Bioethanol production from waste paper through fungal biotechnology
- Authors: Voigt, Paul George
- Date: 2010
- Subjects: Biomass energy , Cellulose -- Biodegradation , Waste paper -- Recycling , Biomass chemicals -- Economic aspects , Renewable energy sources , Fungi -- Biotechnology , Enzymes -- Biotechnology
- Language: English
- Type: Thesis , MSc , Masters
- Identifier: vital:3861 , http://hdl.handle.net/10962/d1013447
- Description: Bioethanol is likely to be a large contributor to the fuel sector of industry in the near future. Current research trends are geared towards utilizing food crops as substrate for bioethanol fermentation; however, this is the source of much controversy. Utilizing food crops for fuel purposes is anticipated to cause massive food shortages worldwide. Cellulose is the most abundant renewable resource on earth and is subject to a wide array of scientific study in order to utilize the glucose contained within it. Waste paper has a high degree of cellulose associated with it, which makes it an ideal target for cellulose biotechnology with the ultimate end goal of bioethanol production. This study focussed on producing the necessary enzymes to hydrolyse the cellulose found in waste paper and using the sugars produced to produce ethanol. The effects of various printing inks had on the production of sugars and the total envirorunental impact of the effluents produced during the production line were also examined. It was found that the fungus Trichoderma longibrachiatum DSM 769 grown in Mandel's medium with waste newspaper as the sole carbon source at 28 °C for 6 days produced extracellular cellulase enzymes with an activity of 0.203 ± 0.009 FPU.ml⁻¹, significantly higher activity as compared to other paper sources. This extracellular cellulase was used to hydrolyse waste newspaper and office paper, with office paper yielding the highest degree of sugar production with an end concentration of 5.80 ± 0.19 g/1 at 40 °C. Analysis by HPLC showed that although glucose was the major product at 4.35 ± 0.12 g/1, cellobiose was also produced in appreciable amounts (1.97 ± 0.71 g/1). The sugar solution was used as a substrate for Saccharomyces cerevisiae DSM 1333 and ethanol was produced at a level of 1.79 ± 0.26 g/1, the presence of which was confirmed by a 600 MHz NMR spectrum. It was found that cellobiose was not fermented by this strain of S. cerevisiae. Certain components of inks (the PAHs phenanthrene and naphthalene) were found to have a slight inhibitory effect (approximately 15% decrease) on the cellulase enzymes at very high concentrations (approximately 600 μg/1 in aqueous medium), while anthracene had no effect. Whole newsprint ink was shown not to sorb glucose. The environmental analysis of the effluents produced showed that in order for the effluents to be discharged into an aqueous ecosystem they would have to be diluted up to 200 times. They were also shown to have the potential to cause severe machinery damage if reused without proper treatment.
- Full Text:
- Date Issued: 2010
- Authors: Voigt, Paul George
- Date: 2010
- Subjects: Biomass energy , Cellulose -- Biodegradation , Waste paper -- Recycling , Biomass chemicals -- Economic aspects , Renewable energy sources , Fungi -- Biotechnology , Enzymes -- Biotechnology
- Language: English
- Type: Thesis , MSc , Masters
- Identifier: vital:3861 , http://hdl.handle.net/10962/d1013447
- Description: Bioethanol is likely to be a large contributor to the fuel sector of industry in the near future. Current research trends are geared towards utilizing food crops as substrate for bioethanol fermentation; however, this is the source of much controversy. Utilizing food crops for fuel purposes is anticipated to cause massive food shortages worldwide. Cellulose is the most abundant renewable resource on earth and is subject to a wide array of scientific study in order to utilize the glucose contained within it. Waste paper has a high degree of cellulose associated with it, which makes it an ideal target for cellulose biotechnology with the ultimate end goal of bioethanol production. This study focussed on producing the necessary enzymes to hydrolyse the cellulose found in waste paper and using the sugars produced to produce ethanol. The effects of various printing inks had on the production of sugars and the total envirorunental impact of the effluents produced during the production line were also examined. It was found that the fungus Trichoderma longibrachiatum DSM 769 grown in Mandel's medium with waste newspaper as the sole carbon source at 28 °C for 6 days produced extracellular cellulase enzymes with an activity of 0.203 ± 0.009 FPU.ml⁻¹, significantly higher activity as compared to other paper sources. This extracellular cellulase was used to hydrolyse waste newspaper and office paper, with office paper yielding the highest degree of sugar production with an end concentration of 5.80 ± 0.19 g/1 at 40 °C. Analysis by HPLC showed that although glucose was the major product at 4.35 ± 0.12 g/1, cellobiose was also produced in appreciable amounts (1.97 ± 0.71 g/1). The sugar solution was used as a substrate for Saccharomyces cerevisiae DSM 1333 and ethanol was produced at a level of 1.79 ± 0.26 g/1, the presence of which was confirmed by a 600 MHz NMR spectrum. It was found that cellobiose was not fermented by this strain of S. cerevisiae. Certain components of inks (the PAHs phenanthrene and naphthalene) were found to have a slight inhibitory effect (approximately 15% decrease) on the cellulase enzymes at very high concentrations (approximately 600 μg/1 in aqueous medium), while anthracene had no effect. Whole newsprint ink was shown not to sorb glucose. The environmental analysis of the effluents produced showed that in order for the effluents to be discharged into an aqueous ecosystem they would have to be diluted up to 200 times. They were also shown to have the potential to cause severe machinery damage if reused without proper treatment.
- Full Text:
- Date Issued: 2010
Isolation and characterization of antiplasmodial metabolites from South African marine alga
- Authors: Afolayan, Anthonia Folake
- Date: 2008
- Subjects: Malaria -- Africa Antimalarials -- Therapeutic use Malaria -- Prevention Malaria -- Drug therapy Marine algae -- Therapeutic use Natural products -- Therapeutic use Plasmodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3739 , http://hdl.handle.net/10962/d1003063
- Description: Malaria is one of the three most deadly diseases in Africa. Although there are available treatments, their efficacy has been greatly reduced over the past two decades due to the development of resistance to currently available drugs. This has necessitated the search for new and effective antimalarial agents. This project approached the search for new antimalarial compounds in two ways: (i) by screening natural products isolated from marine algae against the Plasmodium parasite and (ii) by modification of selected isolated active compounds to target 1-deoxY-đ-xylulose 5-phosphate reductoisomerase (DXR), an enzyme found in the nonmevalonate isoprenoid biosynthetic pathway of Plasmodium Jalciparum. It was envisaged that such a compound would exhibit dual action on the Plasmodium parasite. Extracts obtained from 22 marine algae were prefractionated by solvent partitioning and were screened for anti plasmodial activity against the chloroquine sensitive (CQS) P. Jalciparum D 10 strain. Overall, 50% of the algae screened produced at least one crude fraction with activity against P. Jalciparum. Extracts of the algae Sargassum heterophyllum, Plocamium cornutum, Amphiroa ephedrea and Pterosiphonia cloiophylla gave the most promising results. Fractionation of S. heterophyllum afforded three tetraprenyltoluquinols (3.1, 3.2 and 3.5) and an all-trans-fucoxanthin (3.6). Three new compounds (4.5, 4.6 and 4.7) and two known halogenated monoterpenes (4.1 and 4.4) were isolated from P. cornutum. Each of the isolated compounds from both S. heterophyllum and P. cornutum showed antiplasmodial activity with IC₅₀ values ranging from 2.0 - 15.3 μM for S. heterophyllum and 13 - 230 μM for P. cornutum. Attempts to synthetically modify halogenated monoterpene 4.4 by dihydroxylation and phosphorylation in order to inhibit the DXR enzyme was unsuccessful. However, the hemiterpene analogue (5.42) of the halogenated monoterpenes was successfully phosphorylated and dihydroxylated to give compound 5.45 which showed promising activity against DXR. The result obtained indicated that the proposed phosphorylation and dihydroxylation of the halogenated monoterpene 4.4 would result in the synthesis of a potent DXR inhibitor and therefore a potential antimalarial agent with dual mode of action on the Plasmodium parasite.
- Full Text:
- Date Issued: 2008
- Authors: Afolayan, Anthonia Folake
- Date: 2008
- Subjects: Malaria -- Africa Antimalarials -- Therapeutic use Malaria -- Prevention Malaria -- Drug therapy Marine algae -- Therapeutic use Natural products -- Therapeutic use Plasmodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3739 , http://hdl.handle.net/10962/d1003063
- Description: Malaria is one of the three most deadly diseases in Africa. Although there are available treatments, their efficacy has been greatly reduced over the past two decades due to the development of resistance to currently available drugs. This has necessitated the search for new and effective antimalarial agents. This project approached the search for new antimalarial compounds in two ways: (i) by screening natural products isolated from marine algae against the Plasmodium parasite and (ii) by modification of selected isolated active compounds to target 1-deoxY-đ-xylulose 5-phosphate reductoisomerase (DXR), an enzyme found in the nonmevalonate isoprenoid biosynthetic pathway of Plasmodium Jalciparum. It was envisaged that such a compound would exhibit dual action on the Plasmodium parasite. Extracts obtained from 22 marine algae were prefractionated by solvent partitioning and were screened for anti plasmodial activity against the chloroquine sensitive (CQS) P. Jalciparum D 10 strain. Overall, 50% of the algae screened produced at least one crude fraction with activity against P. Jalciparum. Extracts of the algae Sargassum heterophyllum, Plocamium cornutum, Amphiroa ephedrea and Pterosiphonia cloiophylla gave the most promising results. Fractionation of S. heterophyllum afforded three tetraprenyltoluquinols (3.1, 3.2 and 3.5) and an all-trans-fucoxanthin (3.6). Three new compounds (4.5, 4.6 and 4.7) and two known halogenated monoterpenes (4.1 and 4.4) were isolated from P. cornutum. Each of the isolated compounds from both S. heterophyllum and P. cornutum showed antiplasmodial activity with IC₅₀ values ranging from 2.0 - 15.3 μM for S. heterophyllum and 13 - 230 μM for P. cornutum. Attempts to synthetically modify halogenated monoterpene 4.4 by dihydroxylation and phosphorylation in order to inhibit the DXR enzyme was unsuccessful. However, the hemiterpene analogue (5.42) of the halogenated monoterpenes was successfully phosphorylated and dihydroxylated to give compound 5.45 which showed promising activity against DXR. The result obtained indicated that the proposed phosphorylation and dihydroxylation of the halogenated monoterpene 4.4 would result in the synthesis of a potent DXR inhibitor and therefore a potential antimalarial agent with dual mode of action on the Plasmodium parasite.
- Full Text:
- Date Issued: 2008
Isolation and structure elucidation of halogenated metabolites from Portieria hornemannii and Portieria tripinnata
- Authors: Adam, Mohammed
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64674 , vital:28591
- Description: The red marine algal genus, Portieria, is known to produce a number of potent cytotoxic compounds with anticancer potential. The most important anticancer lead produced by this genus is the compound halomon. Unfortunately, the lack of sufficient quantities of this compound hampered its further development. Two Portieria species, Portieria hornemannii and Portieria tripinnata, are found along the South African coastline. Recent studies, based on DNA analysis, suggest that Portieria hornemannii may in fact be divided into several cryptic species. The current project is part of a larger study designed to investigate the use of secondary metabolites to identify new marine algal species. In this study 1H NMR profiles of the organic extracts of selected Portieria spp were compared in order to identify new species. Selected compounds were then isolated and characterised as potential chemotaxonomic markers. Four halogenated monoterpenes were isolated from Portieria hornemannii. Two of these were new compounds 4-(3-bromo-4-chloro-4-methylpentyl)-3-chlorofuran-2(5H)-one, which were isomers of each other. The two known compounds had been previously isolated from Portieria hornemannii samples off the Madagascar coast. These compounds could prove to be useful as chemotaxonomic marker compounds, as they have never been isolated from any other species of marine algae. Three known halogenated monoterpenes were isolated from Portieria tripinnata. These compounds had been previously isolated from different species of marine algae and therefore, could not serve as chemotaxonomic marker compounds for this species of marine alga. Further work needs to be done on Portieria tripinnata, with regards to its chemistry, as it is a species of marine algae that has not been previously researched.
- Full Text:
- Date Issued: 2015
- Authors: Adam, Mohammed
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64674 , vital:28591
- Description: The red marine algal genus, Portieria, is known to produce a number of potent cytotoxic compounds with anticancer potential. The most important anticancer lead produced by this genus is the compound halomon. Unfortunately, the lack of sufficient quantities of this compound hampered its further development. Two Portieria species, Portieria hornemannii and Portieria tripinnata, are found along the South African coastline. Recent studies, based on DNA analysis, suggest that Portieria hornemannii may in fact be divided into several cryptic species. The current project is part of a larger study designed to investigate the use of secondary metabolites to identify new marine algal species. In this study 1H NMR profiles of the organic extracts of selected Portieria spp were compared in order to identify new species. Selected compounds were then isolated and characterised as potential chemotaxonomic markers. Four halogenated monoterpenes were isolated from Portieria hornemannii. Two of these were new compounds 4-(3-bromo-4-chloro-4-methylpentyl)-3-chlorofuran-2(5H)-one, which were isomers of each other. The two known compounds had been previously isolated from Portieria hornemannii samples off the Madagascar coast. These compounds could prove to be useful as chemotaxonomic marker compounds, as they have never been isolated from any other species of marine algae. Three known halogenated monoterpenes were isolated from Portieria tripinnata. These compounds had been previously isolated from different species of marine algae and therefore, could not serve as chemotaxonomic marker compounds for this species of marine alga. Further work needs to be done on Portieria tripinnata, with regards to its chemistry, as it is a species of marine algae that has not been previously researched.
- Full Text:
- Date Issued: 2015
Isolation, characterization and biomimetic oxidation of selected marine natural products and their analogues
- Authors: Mutsvairo, Tafadzwa
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64685 , vital:28592
- Description: Marine brown algae produce a variety of terpenes with a wide range of biological activities. However, very few phytochemical studies of brown algae have been conducted in South Africa. Therefore, in our continued search for biologically active natural products, we examined the South African brown alga Brassicophycus brassicaeformis. The dichloromethane-methanol extract of B.brassicaeformis was fractionated by silica gel column chromatography followed by normal phase HPLC to give pure four pure compounds which were identified by spectroscopic methods as; fucosterol, fucoxanthin and two monogalactosyldiacylglycerol lipids. Many potential drug molecules such as natural products have failed to reach the market due to poor pharmacokinetic and metabolic profiles despite having potent biological activity. Therefore the importance of early drug metabolism studies in the drug development process is clear. A biomimetic oxidation model was used for in vitro drug metabolism studies to predict any possible metabolites that could be produced by these natural products. Two biomimetic oxidation models catalyzed by two water soluble metalloporphyrins as biomimics of cytochrome P450, in the presence of two terminal oxidants either hydrogen peroxide or iodobenzene diacetete were successfully developed. The models were applied to a range of natural products. The oxidation of the quinone natural products, sargahydroquinoic acid, and lapachol was most easily achieved by metalloporphyrins employed in this study.
- Full Text:
- Date Issued: 2016
- Authors: Mutsvairo, Tafadzwa
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64685 , vital:28592
- Description: Marine brown algae produce a variety of terpenes with a wide range of biological activities. However, very few phytochemical studies of brown algae have been conducted in South Africa. Therefore, in our continued search for biologically active natural products, we examined the South African brown alga Brassicophycus brassicaeformis. The dichloromethane-methanol extract of B.brassicaeformis was fractionated by silica gel column chromatography followed by normal phase HPLC to give pure four pure compounds which were identified by spectroscopic methods as; fucosterol, fucoxanthin and two monogalactosyldiacylglycerol lipids. Many potential drug molecules such as natural products have failed to reach the market due to poor pharmacokinetic and metabolic profiles despite having potent biological activity. Therefore the importance of early drug metabolism studies in the drug development process is clear. A biomimetic oxidation model was used for in vitro drug metabolism studies to predict any possible metabolites that could be produced by these natural products. Two biomimetic oxidation models catalyzed by two water soluble metalloporphyrins as biomimics of cytochrome P450, in the presence of two terminal oxidants either hydrogen peroxide or iodobenzene diacetete were successfully developed. The models were applied to a range of natural products. The oxidation of the quinone natural products, sargahydroquinoic acid, and lapachol was most easily achieved by metalloporphyrins employed in this study.
- Full Text:
- Date Issued: 2016
Isolation, structural characterisation and evaluation of cytotoxic activity of natural products from selected South African marine red algae
- Authors: Knott, Michael George
- Date: 2012
- Subjects: Marine algae -- South Africa , Red algae -- South Africa , Pharmaceutical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3862 , http://hdl.handle.net/10962/d1015460
- Description: The medicinal chemistry of selected marine algae indigenous to South Africa was investigated. Following the isolation and characterisation of a number of new and known compounds, the associated in vitro cytotoxic profiles of these new compounds was investigated. Plocamium maxillosum yielded two new cyclic polyhalogenated monoterpenes which were characterised as 2E-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.1) and 2Z-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.2) on the basis of one and two dimensional NMR spectroscopic data and MS analysis. These compounds were also found to have good cytotoxic activity against breast cancer cell lines. Although these compounds are based on a regular monoterpene skeleton, they represent an uncommon feature not often seen in cyclic halogenated monoterpenes from marine algae. Plocamium robertiae yielded one new cyclic polyhalogenated monoterpene identified as 4,5- dibromo-5-chloromethyl-1-chlorovinyl-2-chloro-methylcyclohexane (2.6) and one known compound called 2,4-dichloro-1-chlorovinyl-1-methylcyclohexane-5-ene or Plocamene D (2.9). Portieria hornemannii was collected from Port Edward in Natal and yielded three new compounds, namely; 3Z-1,6-dibromo-3-(bromomethylidene)-2,7-dichloro-7-methyloctane (3.1), 1E,3Z-1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.2), 1Z,3Z- 1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.3), and one known compound, namely; 3S,6R-6-bromo-3-(bromomethyl)-3,7-dichloro-7-methyloct-1-ene (3.4). Compounds 3.1 and 3.2 showed no cytotoxic activity against breast cancer cells. Another Portieria hornemannii sample was collected from Noordhoek in the Eastern Cape, it yielded one known compound referred to as 3Z-6-bromo-3-(bromomethylidene)-2,7- dichloro-7-methyloct-1-ene (3.5), as well as one new compound called portieric acid A (3.6) or 5-bromo-2-(bromomethylidene)-6-chloro-6-methylheptanoic acid. Portieric acid A showed slight cytotoxic activity and also represents a new class of compound within the genus Portieria. The isolation of secondary metabolites from the South African red alga, Laurencia glomerata, yielded two known compounds; 7-hydroxylaurene (4.9) and cis-neolaurencenyne (4.12), as well as one chamigrane related compound (4.11). Laurencia flexuosa yielded one known compound called 3Z-bromofucin (4.13). Using 1H NMR, GC and molecular systematics, a novel method for identifying different species of Laurencia was also investigated.
- Full Text:
- Date Issued: 2012
- Authors: Knott, Michael George
- Date: 2012
- Subjects: Marine algae -- South Africa , Red algae -- South Africa , Pharmaceutical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3862 , http://hdl.handle.net/10962/d1015460
- Description: The medicinal chemistry of selected marine algae indigenous to South Africa was investigated. Following the isolation and characterisation of a number of new and known compounds, the associated in vitro cytotoxic profiles of these new compounds was investigated. Plocamium maxillosum yielded two new cyclic polyhalogenated monoterpenes which were characterised as 2E-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.1) and 2Z-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.2) on the basis of one and two dimensional NMR spectroscopic data and MS analysis. These compounds were also found to have good cytotoxic activity against breast cancer cell lines. Although these compounds are based on a regular monoterpene skeleton, they represent an uncommon feature not often seen in cyclic halogenated monoterpenes from marine algae. Plocamium robertiae yielded one new cyclic polyhalogenated monoterpene identified as 4,5- dibromo-5-chloromethyl-1-chlorovinyl-2-chloro-methylcyclohexane (2.6) and one known compound called 2,4-dichloro-1-chlorovinyl-1-methylcyclohexane-5-ene or Plocamene D (2.9). Portieria hornemannii was collected from Port Edward in Natal and yielded three new compounds, namely; 3Z-1,6-dibromo-3-(bromomethylidene)-2,7-dichloro-7-methyloctane (3.1), 1E,3Z-1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.2), 1Z,3Z- 1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.3), and one known compound, namely; 3S,6R-6-bromo-3-(bromomethyl)-3,7-dichloro-7-methyloct-1-ene (3.4). Compounds 3.1 and 3.2 showed no cytotoxic activity against breast cancer cells. Another Portieria hornemannii sample was collected from Noordhoek in the Eastern Cape, it yielded one known compound referred to as 3Z-6-bromo-3-(bromomethylidene)-2,7- dichloro-7-methyloct-1-ene (3.5), as well as one new compound called portieric acid A (3.6) or 5-bromo-2-(bromomethylidene)-6-chloro-6-methylheptanoic acid. Portieric acid A showed slight cytotoxic activity and also represents a new class of compound within the genus Portieria. The isolation of secondary metabolites from the South African red alga, Laurencia glomerata, yielded two known compounds; 7-hydroxylaurene (4.9) and cis-neolaurencenyne (4.12), as well as one chamigrane related compound (4.11). Laurencia flexuosa yielded one known compound called 3Z-bromofucin (4.13). Using 1H NMR, GC and molecular systematics, a novel method for identifying different species of Laurencia was also investigated.
- Full Text:
- Date Issued: 2012
Marine biotechnology : evaluation and development of methods for the discovery of natural products from fungi
- Authors: Pather, Simisha
- Date: 2005 , 2013-06-18
- Subjects: Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3839 , http://hdl.handle.net/10962/d1007652 , Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Description: One of the major impediments in the development of marine natural products is the provision of biologically active natural products in sufficient quantity for complete pharmacological evaluation, clinical trials and eventual commercial production. Marine microorganisms show great promise in providing a renewable source of biologically active natural products. The main aim of this study was to develop and evaluate methods for the isolation, identification and cultivation of marine fungi from the South African marine environment for the production of biologically active secondary metabolites. Twenty-four species of fungi were isolated from marine algae collected from the intertidal zone near Port Alfred, South Africa. The fungi were cultivated in small-scale under static and agitated conditions and their crude intra- and extracellular organic extracts were screened by ¹H NMR and a series of bioassays. Using this as a basis, one isolate was selected for further study. By analyses of the lTS1 region of the ribosomal DNA, the fungal isolate was identified as a marine-derived isolate of Eurotium rubrum (Aspergillus ruber). Although E. rubrum has been isolated from the marine environment, no investigations have been undertaken to determine the adaptation of these isolates to the marine environment. In order to optimise productivity, creativity and incubation time, the fungus was cultivated in small-scale using a variety of carbon (glucose, fructose, lactose, sucrose, marmitol and maltose) and nitrogen sources (ammonium tartrate, urea, peptone and yeast extract). An HPLC-DAD method was developed to assess the metabolic creativity and productivity under different fermentation conditions. Distinctive variations in the range and yield of metabolites produced as well as morphology and growth time were observed. The crude extracts from all fermentations were combined and six known compounds were isolated by reversed-phase chromatography and their structures elucidated by spectroscopic techniques. The known compounds were fIavoglaucin, aspergin, isodihydroauroglaucin, isotetrahydroauroglaucin, neoechinuline A and physcion. Neoechinuline A, isodihydroauroglaucin and isotetrahydroauroglaucin showed activity against oesophageal and cervical cancer cell lines.
- Full Text:
- Date Issued: 2005
- Authors: Pather, Simisha
- Date: 2005 , 2013-06-18
- Subjects: Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3839 , http://hdl.handle.net/10962/d1007652 , Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Description: One of the major impediments in the development of marine natural products is the provision of biologically active natural products in sufficient quantity for complete pharmacological evaluation, clinical trials and eventual commercial production. Marine microorganisms show great promise in providing a renewable source of biologically active natural products. The main aim of this study was to develop and evaluate methods for the isolation, identification and cultivation of marine fungi from the South African marine environment for the production of biologically active secondary metabolites. Twenty-four species of fungi were isolated from marine algae collected from the intertidal zone near Port Alfred, South Africa. The fungi were cultivated in small-scale under static and agitated conditions and their crude intra- and extracellular organic extracts were screened by ¹H NMR and a series of bioassays. Using this as a basis, one isolate was selected for further study. By analyses of the lTS1 region of the ribosomal DNA, the fungal isolate was identified as a marine-derived isolate of Eurotium rubrum (Aspergillus ruber). Although E. rubrum has been isolated from the marine environment, no investigations have been undertaken to determine the adaptation of these isolates to the marine environment. In order to optimise productivity, creativity and incubation time, the fungus was cultivated in small-scale using a variety of carbon (glucose, fructose, lactose, sucrose, marmitol and maltose) and nitrogen sources (ammonium tartrate, urea, peptone and yeast extract). An HPLC-DAD method was developed to assess the metabolic creativity and productivity under different fermentation conditions. Distinctive variations in the range and yield of metabolites produced as well as morphology and growth time were observed. The crude extracts from all fermentations were combined and six known compounds were isolated by reversed-phase chromatography and their structures elucidated by spectroscopic techniques. The known compounds were fIavoglaucin, aspergin, isodihydroauroglaucin, isotetrahydroauroglaucin, neoechinuline A and physcion. Neoechinuline A, isodihydroauroglaucin and isotetrahydroauroglaucin showed activity against oesophageal and cervical cancer cell lines.
- Full Text:
- Date Issued: 2005
Synthesis and biological evaluation of truncated sarganaphthoquinoic acid derivatives as Hsp90 inhibitors
- Authors: Chiwakata, Maynard T
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64708 , vital:28594
- Description: Hsp90 inhibition has been at the centre of attention in current research due to the possibility of “cracking down” on the entire process leading to the development of malignant cancers. Small underlying principles common in all types of cancers have been determined that govern the transformation of normal human cells into cancerous cells, with all relying on the ATPase activity of Hsp90 protein. Hsp90 protein is therefore an attractive drug target that if successfully inhibited can result in the remission of cancer tumours by one form of treatment. To date, no Hsp90 inhibitor has been sanctioned for cancer treatment as most are still in clinical development. Our research was therefore inspired by reports that indicated the potential of quinones / naphthoquinones to act as Hsp90 inhibitors. Preliminary results of a few selected marine natural product quinone systems i.e. sargaquinoic acid (SQA) (2.47) and lapachol (3.6) showed moderate cytotoxicity and weak interactions with the Hsp90 molecular chaperone, and evidence suggested C-terminal binding of these molecules. No correlation has been determined yet between cytotoxicity and Hsp90 inhibition, hence we aimed to develop natural product inspired molecules that exhibit both cytotoxic and Hsp90 inhibition properties. Due to limited amounts of the natural product that can be acquired from natural sources, synthetic analogues were opted for. Isolation of a few selected quinones was conducted to have material that could be used in biological assays. For structural modifications, a series of truncated naphthoquinone systems were prepared adopting the sarganaphthoquinoic acid (3.5) scaffold. The naphthoquinones were prepared via Diels-Alder reactions of relevant benzoquinones with myrcene, followed by aromatization reactions using MnO2. Various alkyl and aryl amines were then coupled to the C-2/3 position of the naphthoquinone using Michael’s addition reactions. Tricyclic naphthoquinones were also synthesized from reactions with hypotaurine and citral. Design of the analogues incorporated functionalities from known Hsp90 inhibitors e.g. geldanamycin (2.28) and its analogues. Preliminary results obtained showed that coupling of naphthoquinones with aryl-amines resulted in the most cytotoxic compounds (4.14-4.19) with IC50 values as low as 0.3 μM against Hs578T breast cancer carcinoma (triple negative). Most of the alkyl amines (4.20-4.25) had IC50 values greater than 50 μM except for 4.20 and 4.21 that showed IC50 values of 7.6 μM and 2.6 μM respectively. Tricyclic naphthoquinones (4.28-4.29) showed moderate cytotoxic activity of approximately 10 μM. Hsp90 inhibition was assessed by client protein degradation assays, of which SQA (2.47), showed the best Hsp90 inhibition properties, followed by compound 4.20. The most cytotoxic arylamino-naphthoquinone (4.16) and tricyclic naphthoquinones (4.28-4.29) showed only moderate inhibition. None of the compounds led to Hsp70 induction, suggesting possible binding to the C-terminus of Hsp90. Interactions at the binding site were assessed by molecular docking studies and saturation transfer difference (STD) NMR. Docking studies were conducted on the N-terminus of Hsp90 and better binding was observed for arylamino naphthoquinones (4.14-4.19) than for other series of compounds. Unfortunately, the co-crystal structure for the C-terminus of Hsp90 is unavailable, hence docking study comparisons on both domains could not be conducted. However, STD NMR offered a platform to assess binding interactions between the naphthoquinones and the N- or C-terminal domains of Hsp90. However no interactions were observed at both the N- and C- termini of Hsp90 due to either weak binding of ligands to the protein or poor water solubility of the ligands. From these preliminary results, naphthoquinones bind to Hsp90 protein but conclusive remarks to which terminal domain they bind to could not be made. The best candidate from amongst the series of naphthoquinones prepared that showed moderate cytotoxicity and promising Hsp90 inhibition was compound 4.20. We therefore succeeded in developing a new series of naphthoquinones that possess moderate cytotoxicity and show Hsp90 inhibition.
- Full Text:
- Date Issued: 2015
- Authors: Chiwakata, Maynard T
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64708 , vital:28594
- Description: Hsp90 inhibition has been at the centre of attention in current research due to the possibility of “cracking down” on the entire process leading to the development of malignant cancers. Small underlying principles common in all types of cancers have been determined that govern the transformation of normal human cells into cancerous cells, with all relying on the ATPase activity of Hsp90 protein. Hsp90 protein is therefore an attractive drug target that if successfully inhibited can result in the remission of cancer tumours by one form of treatment. To date, no Hsp90 inhibitor has been sanctioned for cancer treatment as most are still in clinical development. Our research was therefore inspired by reports that indicated the potential of quinones / naphthoquinones to act as Hsp90 inhibitors. Preliminary results of a few selected marine natural product quinone systems i.e. sargaquinoic acid (SQA) (2.47) and lapachol (3.6) showed moderate cytotoxicity and weak interactions with the Hsp90 molecular chaperone, and evidence suggested C-terminal binding of these molecules. No correlation has been determined yet between cytotoxicity and Hsp90 inhibition, hence we aimed to develop natural product inspired molecules that exhibit both cytotoxic and Hsp90 inhibition properties. Due to limited amounts of the natural product that can be acquired from natural sources, synthetic analogues were opted for. Isolation of a few selected quinones was conducted to have material that could be used in biological assays. For structural modifications, a series of truncated naphthoquinone systems were prepared adopting the sarganaphthoquinoic acid (3.5) scaffold. The naphthoquinones were prepared via Diels-Alder reactions of relevant benzoquinones with myrcene, followed by aromatization reactions using MnO2. Various alkyl and aryl amines were then coupled to the C-2/3 position of the naphthoquinone using Michael’s addition reactions. Tricyclic naphthoquinones were also synthesized from reactions with hypotaurine and citral. Design of the analogues incorporated functionalities from known Hsp90 inhibitors e.g. geldanamycin (2.28) and its analogues. Preliminary results obtained showed that coupling of naphthoquinones with aryl-amines resulted in the most cytotoxic compounds (4.14-4.19) with IC50 values as low as 0.3 μM against Hs578T breast cancer carcinoma (triple negative). Most of the alkyl amines (4.20-4.25) had IC50 values greater than 50 μM except for 4.20 and 4.21 that showed IC50 values of 7.6 μM and 2.6 μM respectively. Tricyclic naphthoquinones (4.28-4.29) showed moderate cytotoxic activity of approximately 10 μM. Hsp90 inhibition was assessed by client protein degradation assays, of which SQA (2.47), showed the best Hsp90 inhibition properties, followed by compound 4.20. The most cytotoxic arylamino-naphthoquinone (4.16) and tricyclic naphthoquinones (4.28-4.29) showed only moderate inhibition. None of the compounds led to Hsp70 induction, suggesting possible binding to the C-terminus of Hsp90. Interactions at the binding site were assessed by molecular docking studies and saturation transfer difference (STD) NMR. Docking studies were conducted on the N-terminus of Hsp90 and better binding was observed for arylamino naphthoquinones (4.14-4.19) than for other series of compounds. Unfortunately, the co-crystal structure for the C-terminus of Hsp90 is unavailable, hence docking study comparisons on both domains could not be conducted. However, STD NMR offered a platform to assess binding interactions between the naphthoquinones and the N- or C-terminal domains of Hsp90. However no interactions were observed at both the N- and C- termini of Hsp90 due to either weak binding of ligands to the protein or poor water solubility of the ligands. From these preliminary results, naphthoquinones bind to Hsp90 protein but conclusive remarks to which terminal domain they bind to could not be made. The best candidate from amongst the series of naphthoquinones prepared that showed moderate cytotoxicity and promising Hsp90 inhibition was compound 4.20. We therefore succeeded in developing a new series of naphthoquinones that possess moderate cytotoxicity and show Hsp90 inhibition.
- Full Text:
- Date Issued: 2015
Synthesis, characterisation and biological activity of 2-(methylthiomethyl)anilines, 2-(methylthio)anilines, their Schiff-base derivatives and metal(II) (Co, Ni, Cu) complexes
- Olalekan, Temitope Elizabeth
- Authors: Olalekan, Temitope Elizabeth
- Date: 2013
- Subjects: Aniline , Schiff bases , Ligands , Nuclear magnetic resonance spectroscopy , Chelates , X-ray crystallography , Antimalarials
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4562 , http://hdl.handle.net/10962/d1020868
- Description: A series of 31 sulfur-nitrogen donor ligands and 64 metal(II) complexes have been investigated. The thiomethylated aniline ligands 2–(methylthiomethyl)aniline 2MT and 2–(methylthio)aniline 2MA were synthesized with their substituted derivatives (-Me, -MeO, -Cl, -Br, -NO2) to serve as chelating agents. These ligands behave as bidentate ligands with SN donor group with Co(II), Ni(II) and Cu(II). The Co(II) and Ni(II) complexes have the ML2Cl2 molecular formula while the Cu(II) complexes formed with MLCl2 stoichiometry where L is the bidentate ligand. The ligands and their metal(II) complexes have been characterized by elemental analysis and with spectroscopic techniques. The trend observed in the NMR spectra and IR frequencies of the thiomethylated compounds shows there is a significant difference between the 2MT and 2MA series as a result of sulfur lone pairs extending the conjugation of the aromatic ring in the case of the latter. The effect of the position and electronic nature of ring substituent on the NMR shifts of the amine protons is discussed. The 6- and 5-membered chelate complexes formed by the 2MT and 2MA ligands respectively do not show significant diversity in their spectroscopic properties. From the elemental analysis for the Co(II) and Ni(II) complexes, their compositions reveal 1:2 M:L stoichiometry with 2 chlorine atoms from the respective metal salts. In addition, the spectroscopic data are largely indicative of tetragonally distorted structures for these solid complexes. The X-ray crystallography data reveal the Cu(II) complexes exist as square pyramidal dimers and with long Cu–Cl equitorial bonds fit into the tetragonally distorted octahedral structure. The electrolytic nature of Co(II) and Cu(II) complexes in DMF were found to be similar, they behave as non electrolytes in contrast to Ni(II) complexes which are 1:1 electrolytes. The electronic spectra of these metal(II) complexes were found to be different for both their solid forms and in solutions of DMF and DMSO and this has been discussed. The thiomethylated aniline ligands possess the amine and thioether groups which are present in many known biologically active compounds, hence the biological activity of the ligands and their metal complexes were tested against three strains of bacteria and one fungus. The methoxy-substituted derivatives were found to possess better inhibitory activity and this was similarly reflected in the metal(II) complexes. The activity of the complexes can be said to be in the order, Cu(II) > Co(II) > Ni(II). The Schiff-base derivatives were prepared from the ligands and para-methoxysalicylaldehyde and their Cu(II) complexes were synthesized in order to determine their biological activity. The Schiff-base ligands were found to be less active than their parent ligands. The Cu(II) complexes are not soluble in water, DMSO or DMF, as a result and could not be evaluated for their biological activity. Based on the good results from the antimicrobial evaluation, the antiplasmodial activity of some of the Co(II), Ni(II) and Cu(II) complexes of the thiomethylated ligands against Plasmodium falciparum (FCR-3) was determined. At 50 μM concentration level, the Cu(II) complexes show activity equal or better than the prophylactic chloroquine. The Cu(II) complexes with the methoxy-substituted demonstrated exceptional activity but their Co(II) and Ni(II) analogues did not show any activity. The cytotoxicity of the active Cu(II) complexes at 50 μM concentration was determined against the breast cancer cell line (MDA-MB-231). The compounds destroyed the cancer cell in the range of 28–40%, thus showing their preferred activity against the parasitic cell instead of the cancer cell. The selectivity demonstrated by these compounds have shown them to be potential antimalarial agents and this could be further investigated.
- Full Text:
- Date Issued: 2013
- Authors: Olalekan, Temitope Elizabeth
- Date: 2013
- Subjects: Aniline , Schiff bases , Ligands , Nuclear magnetic resonance spectroscopy , Chelates , X-ray crystallography , Antimalarials
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4562 , http://hdl.handle.net/10962/d1020868
- Description: A series of 31 sulfur-nitrogen donor ligands and 64 metal(II) complexes have been investigated. The thiomethylated aniline ligands 2–(methylthiomethyl)aniline 2MT and 2–(methylthio)aniline 2MA were synthesized with their substituted derivatives (-Me, -MeO, -Cl, -Br, -NO2) to serve as chelating agents. These ligands behave as bidentate ligands with SN donor group with Co(II), Ni(II) and Cu(II). The Co(II) and Ni(II) complexes have the ML2Cl2 molecular formula while the Cu(II) complexes formed with MLCl2 stoichiometry where L is the bidentate ligand. The ligands and their metal(II) complexes have been characterized by elemental analysis and with spectroscopic techniques. The trend observed in the NMR spectra and IR frequencies of the thiomethylated compounds shows there is a significant difference between the 2MT and 2MA series as a result of sulfur lone pairs extending the conjugation of the aromatic ring in the case of the latter. The effect of the position and electronic nature of ring substituent on the NMR shifts of the amine protons is discussed. The 6- and 5-membered chelate complexes formed by the 2MT and 2MA ligands respectively do not show significant diversity in their spectroscopic properties. From the elemental analysis for the Co(II) and Ni(II) complexes, their compositions reveal 1:2 M:L stoichiometry with 2 chlorine atoms from the respective metal salts. In addition, the spectroscopic data are largely indicative of tetragonally distorted structures for these solid complexes. The X-ray crystallography data reveal the Cu(II) complexes exist as square pyramidal dimers and with long Cu–Cl equitorial bonds fit into the tetragonally distorted octahedral structure. The electrolytic nature of Co(II) and Cu(II) complexes in DMF were found to be similar, they behave as non electrolytes in contrast to Ni(II) complexes which are 1:1 electrolytes. The electronic spectra of these metal(II) complexes were found to be different for both their solid forms and in solutions of DMF and DMSO and this has been discussed. The thiomethylated aniline ligands possess the amine and thioether groups which are present in many known biologically active compounds, hence the biological activity of the ligands and their metal complexes were tested against three strains of bacteria and one fungus. The methoxy-substituted derivatives were found to possess better inhibitory activity and this was similarly reflected in the metal(II) complexes. The activity of the complexes can be said to be in the order, Cu(II) > Co(II) > Ni(II). The Schiff-base derivatives were prepared from the ligands and para-methoxysalicylaldehyde and their Cu(II) complexes were synthesized in order to determine their biological activity. The Schiff-base ligands were found to be less active than their parent ligands. The Cu(II) complexes are not soluble in water, DMSO or DMF, as a result and could not be evaluated for their biological activity. Based on the good results from the antimicrobial evaluation, the antiplasmodial activity of some of the Co(II), Ni(II) and Cu(II) complexes of the thiomethylated ligands against Plasmodium falciparum (FCR-3) was determined. At 50 μM concentration level, the Cu(II) complexes show activity equal or better than the prophylactic chloroquine. The Cu(II) complexes with the methoxy-substituted demonstrated exceptional activity but their Co(II) and Ni(II) analogues did not show any activity. The cytotoxicity of the active Cu(II) complexes at 50 μM concentration was determined against the breast cancer cell line (MDA-MB-231). The compounds destroyed the cancer cell in the range of 28–40%, thus showing their preferred activity against the parasitic cell instead of the cancer cell. The selectivity demonstrated by these compounds have shown them to be potential antimalarial agents and this could be further investigated.
- Full Text:
- Date Issued: 2013
The chemistry of Algoa Bay ascidians
- Authors: Bromley, Candice Leigh
- Date: 2016
- Subjects: Sea squirts -- South Africa -- Algoa Bay , Marine metabolites , Chemistry, Analytic , Liquid chromatography , Inductively coupled plasma mass spectrometry , Metal ions , Nucleosides , Vanadium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4560 , http://hdl.handle.net/10962/d1020606
- Description: This thesis investigates the chemistry of 25 ascidian species collected from Algoa Bay, South Africa with a concerted focus on metal accumulation by these ascidians and the possible interaction of these metals with ascidian metabolites. Chapter 2 details the screening techniques employed to establish the presence of nitrogenous metabolites (1H- 15N HMBC), hyper-accumulated metal ions (ICP-MS) and potential metal ion/ ascidian metabolite complexes (LC-ICP-MS/ESI-MS). Unfortunately, exhaustive attempts to detect intact metal ion/ascidian metabolite complexes through the use of liquid chromatography with parallel inductively coupled plasma mass spectrometry/electrospray mass spectrometry (LC-ICPMS/ ESI-MS) were unsuccessful. However, the LC-ICP-MS/ESI-MS data obtained for the crude organic extracts of six of the Algoa Bay ascidian species, Distaplia skoogi, Aplidium monile, Aplidium sp., Didemnum sp., Leptoclindines sp. and Polycitor sp. enabled identification of a number of ten halogenated metabolites, namely the indoles 2.28-2.30, and the tyramine and tyrosine derivatives (2.31-2.33, 2.41, 2.43, 2.44 and 2.46), within the ascidian extracts. This study confirmed that LC-ICP-MS/ESI-MS is a powerful tool for the dereplication of halogenated metabolites in complex mixtures especially where these compounds are present in very small amounts. This study is also the first report of these compounds (eight of which are known) in African ascidians. Compounds 2.32 and 2.46 have not been reported before from a marine source. Compounds 2.28-2.30 and 2.33 were present in sufficient amounts in the respective ascidian extracts to allow their isolation and structure elucidation using standard spectroscopic techniques Chapter 3 explores the ability of ascidians to accumulate a wide range of metal ions at concentrations which are often orders of magnitude higher than those of the surrounding sea water. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the total ion concentrations of 24 metals in 25 Algoa Bay ascidian species. To the best of our knowledge this is the largest and most extensive investigation of metal concentrations in a group of different ascidians occurring in the same area. Hypotheisizing that the metal ion concentrations for each ascidian specimen screened may represent a unique fingerprint for each specimen principal component analysis (PCA) was used in an attempt to establish whether there were spatial, temporal or phylogenetic relationships associated with the metal concentration fingerprints of the ascidians that formed part of this study. The PCA results showed that there were no statistically significant relationships between ascidian metal ion concentrations and either the collection year or the collection site of the ascidians. However, species from the family Didemnidae provided the clearest statistical evidence supporting a phylogenetic relationship between these ascidians and their hyperaccumulated metal ion profiles. Furthermore, these results suggested that ascidian species are indeed actively concentrating metal ions from the surrounding sea water and are not simply sinks for passively accumulated metal ions. Interestingly, the concentration of vanadium in the set of ascidians studied did not appear to correlate with any of the other metals accumulated by these ascidians suggesting that there is possibly a unique method employed for the accumulation of vanadium by ascidians. Chapter 4 investigated this possibility further after the nucleosides 4.10, 4.11, 4.13, 4.15, 4.17 and 4.40 were isolated from the vanadium accumulating ascidian Aplidium monile. Studies into the interactions between nucleosides and vanadyl are unfortunately rare and usually qualitative in nature with limited information provided about the stability or structures of the complexes formed. The vanadyl accumulating aplousobranch ascidians e.g. Aplidium monile dominated our study of Algoa Bay ascidians therefore providing us with the rationale to investigate the relatively little studied binding ability and stability of vandyl-nucleoside complexes. Potentiometric studies were conducted to determine the stability constants of complexes formed between the oxovanadium ion vanadyl (VO2+) and the commercially available nucleosides 4.10-4.14. The data afforded by this analysis clearly confirmed the complexity of the vanadyl/nucleoside complexation and suggested that guanosine (4.12) formed the most stable complex with oxovanadium ions. We were also able to establish a third protonation constant for the hydroxyl moiety in 4.12 with a logK 8.87 which has not been previously reported. Finally, Chapter 5 revisited the cytoxicity two Algoa Bay ascidians, Clavelina sp. and Atriolum marinense the extracts from which produced promising bioactivity results in previous studies against oesophageal cancer cells. The HP-20 fractionated extracts of Clavelina sp. and Atriolum marinense proved to be similalrly cytotoxic to breast cancer cells. With the exception for the 100% acetone(aq)fractions the NMR data for both species suggested that most active non polar fractions were dominated by what appeared to be structurally unremarkable fatty acid glycerides and as such were not pursued further. Purification of the 100% acetone(aq)fraction of A. marinense resulted in the isolation of a styrene trimer, 5.1, common to both ascidian extracts. The NMR simulation software WIN-DAISY was employed to confirm the structure of 5.1. Attempts to establish if 5.1 was an isolation artefact or a product of marine pollution were inconclusive
- Full Text:
- Date Issued: 2016
- Authors: Bromley, Candice Leigh
- Date: 2016
- Subjects: Sea squirts -- South Africa -- Algoa Bay , Marine metabolites , Chemistry, Analytic , Liquid chromatography , Inductively coupled plasma mass spectrometry , Metal ions , Nucleosides , Vanadium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4560 , http://hdl.handle.net/10962/d1020606
- Description: This thesis investigates the chemistry of 25 ascidian species collected from Algoa Bay, South Africa with a concerted focus on metal accumulation by these ascidians and the possible interaction of these metals with ascidian metabolites. Chapter 2 details the screening techniques employed to establish the presence of nitrogenous metabolites (1H- 15N HMBC), hyper-accumulated metal ions (ICP-MS) and potential metal ion/ ascidian metabolite complexes (LC-ICP-MS/ESI-MS). Unfortunately, exhaustive attempts to detect intact metal ion/ascidian metabolite complexes through the use of liquid chromatography with parallel inductively coupled plasma mass spectrometry/electrospray mass spectrometry (LC-ICPMS/ ESI-MS) were unsuccessful. However, the LC-ICP-MS/ESI-MS data obtained for the crude organic extracts of six of the Algoa Bay ascidian species, Distaplia skoogi, Aplidium monile, Aplidium sp., Didemnum sp., Leptoclindines sp. and Polycitor sp. enabled identification of a number of ten halogenated metabolites, namely the indoles 2.28-2.30, and the tyramine and tyrosine derivatives (2.31-2.33, 2.41, 2.43, 2.44 and 2.46), within the ascidian extracts. This study confirmed that LC-ICP-MS/ESI-MS is a powerful tool for the dereplication of halogenated metabolites in complex mixtures especially where these compounds are present in very small amounts. This study is also the first report of these compounds (eight of which are known) in African ascidians. Compounds 2.32 and 2.46 have not been reported before from a marine source. Compounds 2.28-2.30 and 2.33 were present in sufficient amounts in the respective ascidian extracts to allow their isolation and structure elucidation using standard spectroscopic techniques Chapter 3 explores the ability of ascidians to accumulate a wide range of metal ions at concentrations which are often orders of magnitude higher than those of the surrounding sea water. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the total ion concentrations of 24 metals in 25 Algoa Bay ascidian species. To the best of our knowledge this is the largest and most extensive investigation of metal concentrations in a group of different ascidians occurring in the same area. Hypotheisizing that the metal ion concentrations for each ascidian specimen screened may represent a unique fingerprint for each specimen principal component analysis (PCA) was used in an attempt to establish whether there were spatial, temporal or phylogenetic relationships associated with the metal concentration fingerprints of the ascidians that formed part of this study. The PCA results showed that there were no statistically significant relationships between ascidian metal ion concentrations and either the collection year or the collection site of the ascidians. However, species from the family Didemnidae provided the clearest statistical evidence supporting a phylogenetic relationship between these ascidians and their hyperaccumulated metal ion profiles. Furthermore, these results suggested that ascidian species are indeed actively concentrating metal ions from the surrounding sea water and are not simply sinks for passively accumulated metal ions. Interestingly, the concentration of vanadium in the set of ascidians studied did not appear to correlate with any of the other metals accumulated by these ascidians suggesting that there is possibly a unique method employed for the accumulation of vanadium by ascidians. Chapter 4 investigated this possibility further after the nucleosides 4.10, 4.11, 4.13, 4.15, 4.17 and 4.40 were isolated from the vanadium accumulating ascidian Aplidium monile. Studies into the interactions between nucleosides and vanadyl are unfortunately rare and usually qualitative in nature with limited information provided about the stability or structures of the complexes formed. The vanadyl accumulating aplousobranch ascidians e.g. Aplidium monile dominated our study of Algoa Bay ascidians therefore providing us with the rationale to investigate the relatively little studied binding ability and stability of vandyl-nucleoside complexes. Potentiometric studies were conducted to determine the stability constants of complexes formed between the oxovanadium ion vanadyl (VO2+) and the commercially available nucleosides 4.10-4.14. The data afforded by this analysis clearly confirmed the complexity of the vanadyl/nucleoside complexation and suggested that guanosine (4.12) formed the most stable complex with oxovanadium ions. We were also able to establish a third protonation constant for the hydroxyl moiety in 4.12 with a logK 8.87 which has not been previously reported. Finally, Chapter 5 revisited the cytoxicity two Algoa Bay ascidians, Clavelina sp. and Atriolum marinense the extracts from which produced promising bioactivity results in previous studies against oesophageal cancer cells. The HP-20 fractionated extracts of Clavelina sp. and Atriolum marinense proved to be similalrly cytotoxic to breast cancer cells. With the exception for the 100% acetone(aq)fractions the NMR data for both species suggested that most active non polar fractions were dominated by what appeared to be structurally unremarkable fatty acid glycerides and as such were not pursued further. Purification of the 100% acetone(aq)fraction of A. marinense resulted in the isolation of a styrene trimer, 5.1, common to both ascidian extracts. The NMR simulation software WIN-DAISY was employed to confirm the structure of 5.1. Attempts to establish if 5.1 was an isolation artefact or a product of marine pollution were inconclusive
- Full Text:
- Date Issued: 2016
The design, synthesis and antiplasmodial activity of a series of halogenated fosmidomycin analogues and hybrid drugs
- Authors: Afolayan, Anthonia Folake
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64370 , vital:28538
- Description: Malaria continues to be a devastating disease and a major cause of death in sub-Saharan Africa. With resistance against most of the available antimalarial drugs, there is a need for ongoing research and development of antimalarial agents. Fosmidomycin and its acetyl analogue FR900098 have been identified as potent inhibitors of Plasmodium falciparum, the causative agent of the most deadly form of malaria. Clinical trials of these agents have revealed poor absorption due to their high hydrophilicity. In the present studies the effect of halogenation of the acyl chain as well as the biological effect of extending the acyl sidechain was explored. This provided the basis on which fosmidomycin hybrids were designed to investigate the feasibility of hybrid extending into NADPH binding pocket. Synthesis of a series of halogenated FR900098 analogues was carried out in three stages. This included i) The introduction of the phosphonate group by reaction with 1,3dibromopropane in an Arbuzov reaction, ii) The introduction of a hydroxamate group by reaction of the propyl phosphonate by means of a nucleophilic substitution reaction with BocNHOBn and iii) The introduction of a halogenated acyl side chain on a protected fosmidomycin backbone. The synthesis of fosmidomycin-hybrids for which chloroquinefosmidomycin hybrids were used as the prototype, involved convergence of the two separately constructed moieties i.e. fosmidomycin and the quinoline moieties in a covalent linkage. The quinoline moiety was easily synthesized from the reaction of 4,7dichloroquinoline with 1,2-diamino ethane. The aminoquinoline so formed resulted in chloroquine-fosmidomycin hybrids 3.8 and 3.9 when reacted with halogenated FR900098 analogues. Antiplasmodial assays were conducted on the chloroquine-fosmidomycin hybrids and the halogenated fosmidomycin derivatives against the chloroquine resistant Gambian FCR-3 strain of P. falciparum. The most potent iodoacetyl fosmidomycin analogues 2.21 gave an IC50 value of 5.54 µM which is eight times more potent than the known antiplasmodial FR900098 which gave an IC50 value of 41.67 µM. All the halogenated FR900098 analogues showed better antiplasmodial activity than their non-halogenated derivatives. This indicated that the presence of halogens in the FR900098 analogues contributes to their biological Chapter 1 Literature review activity. The acetyl and propyl linked hybrids 3.8 and 3.9 showed potent antiplasmodial activity with IC50 values of 0.18 and 0.82 µM respectively. These were by far the most potent hybrids synthesized and provided leads for a new class of promising antimalarial agents. Preliminary E. coli DXR enzyme inhibition assays were carried out on the halogenated fosmidomycin analogues. The results showed good inhibition of the enzyme by the phosphonic acids of the chloroacetyl and chloropropyl analogues 2.1 and 2.2 respectively. Molecular modelling of the compounds on E. coli (PDB code: 2EGH) and P. falciparum (PDB code: 3AUA) DXR showed strong binding of the halogenated fosmidomycin analogues while the hybrids in the absence of docked NADPH showed minimum binding to the enzymes.
- Full Text:
- Date Issued: 2012
- Authors: Afolayan, Anthonia Folake
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64370 , vital:28538
- Description: Malaria continues to be a devastating disease and a major cause of death in sub-Saharan Africa. With resistance against most of the available antimalarial drugs, there is a need for ongoing research and development of antimalarial agents. Fosmidomycin and its acetyl analogue FR900098 have been identified as potent inhibitors of Plasmodium falciparum, the causative agent of the most deadly form of malaria. Clinical trials of these agents have revealed poor absorption due to their high hydrophilicity. In the present studies the effect of halogenation of the acyl chain as well as the biological effect of extending the acyl sidechain was explored. This provided the basis on which fosmidomycin hybrids were designed to investigate the feasibility of hybrid extending into NADPH binding pocket. Synthesis of a series of halogenated FR900098 analogues was carried out in three stages. This included i) The introduction of the phosphonate group by reaction with 1,3dibromopropane in an Arbuzov reaction, ii) The introduction of a hydroxamate group by reaction of the propyl phosphonate by means of a nucleophilic substitution reaction with BocNHOBn and iii) The introduction of a halogenated acyl side chain on a protected fosmidomycin backbone. The synthesis of fosmidomycin-hybrids for which chloroquinefosmidomycin hybrids were used as the prototype, involved convergence of the two separately constructed moieties i.e. fosmidomycin and the quinoline moieties in a covalent linkage. The quinoline moiety was easily synthesized from the reaction of 4,7dichloroquinoline with 1,2-diamino ethane. The aminoquinoline so formed resulted in chloroquine-fosmidomycin hybrids 3.8 and 3.9 when reacted with halogenated FR900098 analogues. Antiplasmodial assays were conducted on the chloroquine-fosmidomycin hybrids and the halogenated fosmidomycin derivatives against the chloroquine resistant Gambian FCR-3 strain of P. falciparum. The most potent iodoacetyl fosmidomycin analogues 2.21 gave an IC50 value of 5.54 µM which is eight times more potent than the known antiplasmodial FR900098 which gave an IC50 value of 41.67 µM. All the halogenated FR900098 analogues showed better antiplasmodial activity than their non-halogenated derivatives. This indicated that the presence of halogens in the FR900098 analogues contributes to their biological Chapter 1 Literature review activity. The acetyl and propyl linked hybrids 3.8 and 3.9 showed potent antiplasmodial activity with IC50 values of 0.18 and 0.82 µM respectively. These were by far the most potent hybrids synthesized and provided leads for a new class of promising antimalarial agents. Preliminary E. coli DXR enzyme inhibition assays were carried out on the halogenated fosmidomycin analogues. The results showed good inhibition of the enzyme by the phosphonic acids of the chloroacetyl and chloropropyl analogues 2.1 and 2.2 respectively. Molecular modelling of the compounds on E. coli (PDB code: 2EGH) and P. falciparum (PDB code: 3AUA) DXR showed strong binding of the halogenated fosmidomycin analogues while the hybrids in the absence of docked NADPH showed minimum binding to the enzymes.
- Full Text:
- Date Issued: 2012
The investigation of novel marine microorganisms for the production of biologically active metabolites
- Authors: Sunkel, Vanessa Ann
- Date: 2009 , 2013-07-15
- Subjects: Antibiotics , Drugs -- Research , Metabolites , Marine biotechnology , Marine metabolites -- Therapeutic use , Microorganisms -- Effect of drugs on , Penicillium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3812 , http://hdl.handle.net/10962/d1004579 , Antibiotics , Drugs -- Research , Metabolites , Marine biotechnology , Marine metabolites -- Therapeutic use , Microorganisms -- Effect of drugs on , Penicillium
- Description: New drugs, particularly antibiotics, are urgently required to combat the increasing problem of antibiotic resistant human pathogens. Due to the scarcity of products available today, the pharmaceutical industry is now under pressure to reassess compounds derived from plants, soil and marine organisms. Pharmaceutical companies are showing renewed interest in marine biotechnology as the oceans represent a rich source of both biological and chemical diversity of novel molecular structures with anti-cancer, anti-inflammatory and antibiotic properties. Formerly unexplored locations, such as deep ocean sediments, show great potential as a source of genetically novel microorganisms producing structurally unique secondary metabolites. In this research, a metabolite producing marine Pseudoalteromonas strain, known as AP5, was initially used to develop methods for the detection, optimisation of production and extraction of bioactive metabolites from other potentially novel marine isolates. Two hundred and seventy six (276) marine isolates from water and sediment samples from the Antarctic Ocean and Marion Island were isolated. Ten visually different isolates were screened for bioactivity against Gram-positive and -negative bacteria, fungi and yeast. Three out of the 10 isolates, WL61 , WL 114 and WL 136, appeared to be novel Streptomyces spp. showing activity against different test organisms. Many of these marine microorganisms are difficult to culture in the laboratory, particularly when they are cultivated continuously in shake flasks as they can stop producing bioactive compounds. The cultivation of marine isolates in bioreactors may be a more beneficial process for the optimisation of metabolite production compared to conventional liquid fermentation techniques whereby the solid-liquid-air interface of membrane bioreactors can imitate the natural environment of microbes. The membrane bioreactor system is a stable growth environment with low shear that supports steady-state biofilm growth consisting of a high cell density due to a high mass transfer of nutrients and oxygen to the cells. This approach was employed and isolates WL61, WL114 and WL136 were immobilised onto ceramic membranes using Quorus single fibre bioreactors (SFR). The SFRs were used to establish the most suitable growth medium for continuous secondary metabolite production. The best growth conditions were applied to the Quorus multifibre bioreactor (MFR) for scale up of biologically active metabolites, highlighting the potential of bioreactor technology for use in bioprospecting for isolating and screening novel and known organisms for new and interesting natural products. Furthermore, the Quorus MFR was shown to be suitable for the production of high yields of antimicrobial metabolites and is an efficient new fermentation production system. Purification by HPLC fractionation was used to characterise four major compounds from isolate WL 114 extracts. NMR structure elucidation identified one of the two primary compounds as Bisphenol A. The complete chemical structure for the second potent bioactive compound could not be determined due to the low concentration and volume of material. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2009
- Authors: Sunkel, Vanessa Ann
- Date: 2009 , 2013-07-15
- Subjects: Antibiotics , Drugs -- Research , Metabolites , Marine biotechnology , Marine metabolites -- Therapeutic use , Microorganisms -- Effect of drugs on , Penicillium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3812 , http://hdl.handle.net/10962/d1004579 , Antibiotics , Drugs -- Research , Metabolites , Marine biotechnology , Marine metabolites -- Therapeutic use , Microorganisms -- Effect of drugs on , Penicillium
- Description: New drugs, particularly antibiotics, are urgently required to combat the increasing problem of antibiotic resistant human pathogens. Due to the scarcity of products available today, the pharmaceutical industry is now under pressure to reassess compounds derived from plants, soil and marine organisms. Pharmaceutical companies are showing renewed interest in marine biotechnology as the oceans represent a rich source of both biological and chemical diversity of novel molecular structures with anti-cancer, anti-inflammatory and antibiotic properties. Formerly unexplored locations, such as deep ocean sediments, show great potential as a source of genetically novel microorganisms producing structurally unique secondary metabolites. In this research, a metabolite producing marine Pseudoalteromonas strain, known as AP5, was initially used to develop methods for the detection, optimisation of production and extraction of bioactive metabolites from other potentially novel marine isolates. Two hundred and seventy six (276) marine isolates from water and sediment samples from the Antarctic Ocean and Marion Island were isolated. Ten visually different isolates were screened for bioactivity against Gram-positive and -negative bacteria, fungi and yeast. Three out of the 10 isolates, WL61 , WL 114 and WL 136, appeared to be novel Streptomyces spp. showing activity against different test organisms. Many of these marine microorganisms are difficult to culture in the laboratory, particularly when they are cultivated continuously in shake flasks as they can stop producing bioactive compounds. The cultivation of marine isolates in bioreactors may be a more beneficial process for the optimisation of metabolite production compared to conventional liquid fermentation techniques whereby the solid-liquid-air interface of membrane bioreactors can imitate the natural environment of microbes. The membrane bioreactor system is a stable growth environment with low shear that supports steady-state biofilm growth consisting of a high cell density due to a high mass transfer of nutrients and oxygen to the cells. This approach was employed and isolates WL61, WL114 and WL136 were immobilised onto ceramic membranes using Quorus single fibre bioreactors (SFR). The SFRs were used to establish the most suitable growth medium for continuous secondary metabolite production. The best growth conditions were applied to the Quorus multifibre bioreactor (MFR) for scale up of biologically active metabolites, highlighting the potential of bioreactor technology for use in bioprospecting for isolating and screening novel and known organisms for new and interesting natural products. Furthermore, the Quorus MFR was shown to be suitable for the production of high yields of antimicrobial metabolites and is an efficient new fermentation production system. Purification by HPLC fractionation was used to characterise four major compounds from isolate WL 114 extracts. NMR structure elucidation identified one of the two primary compounds as Bisphenol A. The complete chemical structure for the second potent bioactive compound could not be determined due to the low concentration and volume of material. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2009
The isolation and characterisation of secondary metabolites from selected South African marine red algae (Rhodophyta)
- Authors: Fakee, Jameel
- Date: 2013
- Subjects: Metabolites Marine algae -- South Africa Marine algae -- Therapeutic use Metabolites -- Therapeutic use Marine metabolites Plocamocera Red algae Laurencia Delisea flaccida
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3733 , http://hdl.handle.net/10962/d1001472
- Description: Secondary metabolites from natural sources are fast growing as popular drug leads. The structural novelty and favourable biological activity that these compounds display contribute to their popularity as drugs of the future. Examples of such compounds include the potent anticancer drug paclitaxel isolated from the bark of a yew tree as well as the more commonly known analgesic aspirin which stems from the bark of the willow tree. The biological activities exhibited by these secondary metabolites are vast and range from antimicrobial to anticancer activity to mention but a few. As a result, the isolation of novel compounds from natural sources is on the rise. The South African seaboard is home to a wealth of various marine algal species which produce fascinating secondary metabolites. For example, Portierria hornemanii was shown to produce halomon, a halogenated monoterpene which has displayed promising cytotoxic activity. This study thus focused primarily on pursuing novel compounds from three endemic South African marine algal species which have never been analysed previously from a chemical perspective. These are Plocamium rigidum (Bory de Saint-Vincent), Laurencia natalensis (Kylin) and Delisea flaccida (Suhr) Papenfuss. Four known compounds and one new halogenated monoterpene, (2E,5E,7Z)-8-chloro- 7-(dichloromethyl)-4-hydroxy-3-methylocta-2,5,7-trienal, were isolated from Plocamium rigidum. The breast cancer (MCF-7 cell line) inhibitory activity for these compounds was assessed and it was observed that an increase in the lipophilic nature of the compounds produced more favourable IC50 values. A pre-cursor to bromofucin type compounds, cis-laurencenyne, was isolated from Laurencia natalensis, as well as a new acetoxy chamigrane type compound, 4-bromo- 3,10-dichloro-7-hydroxy-3,7,11,11-tetramethylspiro [6.6] undec-1-yl acetate. Delisea flaccida was seen to contain two known bromofuranone type compounds isolated as an isomeric mixture, 1-[(5Z)-4-bromo-5-(bromomethylidene)-2-oxo-2,5- dihydrofuran-3-yl] butyl acetate and 1-[(5E)-4-bromo-5-(bromomethylidene)-2- oxo-2,5-dihydrofuran-3-yl]butyl acetate. These compounds are famous for their ability to inhibit bacterial biofilm production and they have been isolated before from an Australian Delisea spp , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: Fakee, Jameel
- Date: 2013
- Subjects: Metabolites Marine algae -- South Africa Marine algae -- Therapeutic use Metabolites -- Therapeutic use Marine metabolites Plocamocera Red algae Laurencia Delisea flaccida
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3733 , http://hdl.handle.net/10962/d1001472
- Description: Secondary metabolites from natural sources are fast growing as popular drug leads. The structural novelty and favourable biological activity that these compounds display contribute to their popularity as drugs of the future. Examples of such compounds include the potent anticancer drug paclitaxel isolated from the bark of a yew tree as well as the more commonly known analgesic aspirin which stems from the bark of the willow tree. The biological activities exhibited by these secondary metabolites are vast and range from antimicrobial to anticancer activity to mention but a few. As a result, the isolation of novel compounds from natural sources is on the rise. The South African seaboard is home to a wealth of various marine algal species which produce fascinating secondary metabolites. For example, Portierria hornemanii was shown to produce halomon, a halogenated monoterpene which has displayed promising cytotoxic activity. This study thus focused primarily on pursuing novel compounds from three endemic South African marine algal species which have never been analysed previously from a chemical perspective. These are Plocamium rigidum (Bory de Saint-Vincent), Laurencia natalensis (Kylin) and Delisea flaccida (Suhr) Papenfuss. Four known compounds and one new halogenated monoterpene, (2E,5E,7Z)-8-chloro- 7-(dichloromethyl)-4-hydroxy-3-methylocta-2,5,7-trienal, were isolated from Plocamium rigidum. The breast cancer (MCF-7 cell line) inhibitory activity for these compounds was assessed and it was observed that an increase in the lipophilic nature of the compounds produced more favourable IC50 values. A pre-cursor to bromofucin type compounds, cis-laurencenyne, was isolated from Laurencia natalensis, as well as a new acetoxy chamigrane type compound, 4-bromo- 3,10-dichloro-7-hydroxy-3,7,11,11-tetramethylspiro [6.6] undec-1-yl acetate. Delisea flaccida was seen to contain two known bromofuranone type compounds isolated as an isomeric mixture, 1-[(5Z)-4-bromo-5-(bromomethylidene)-2-oxo-2,5- dihydrofuran-3-yl] butyl acetate and 1-[(5E)-4-bromo-5-(bromomethylidene)-2- oxo-2,5-dihydrofuran-3-yl]butyl acetate. These compounds are famous for their ability to inhibit bacterial biofilm production and they have been isolated before from an Australian Delisea spp , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
The isolation, characterisation and chemotaxonomic significance of secondary metabolites from selected South African Laurencia spp. Rhodophyta
- Authors: Fakee, Jameel
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64696 , vital:28593
- Description: Bioprospection of marine organisms as a potential source for lead drugs is becoming increasingly popular. The secondary metabolome of these organisms consists of structurally diverse molecules possessing unprecedented carbon skeletons, the biosynthesis of which occurs via complex metabolomic pathways driven by specialist enzymes. This structural novelty is highly influential on the favourable bioactivity these compounds display. A prominent example of such a compound is trabectedin marketed as Yondelis®. Registered for the treatment of soft tissue sarcomas, this marine drug was developed from extracts of the tunicate Ecteinascidia turbinata. South Africa is renowned for possessing a highly diverse marine biota including several endemic species of marine red algae belonging to the Laurencia sensu stricto genus, which falls within the Laurencia complex. Despite having a good reputation for fascinating secondary metabolites, the taxonomy of Laurencia natural products is proving challenging for reasons including the presence of cryptic species, as well as individual species displaying morphological variability. The aim of this study was thus to isolate secondary metabolites from various South African Laurencia spp. and subsequently assess their chemotaxonomic significance by analysis of a parallel plastid rbcL phylogeny study of Laurencia spp. This study reports the first phycochemical investigation into Laurencia natalensis Kylin, Laurencia cf. corymbosa J.Agardh, Laurencia complanata (Suhr) Kützing, Laurencia sodwaniensis Francis, Bolton, Mattio and Anderson submitted, Laurencia multiclavata Francis, Bolton, Mattio and Anderson submitted, and a South African specimen of Laurenciella marilzae Gil-Rodríguez, Sentíes, Díaz-Larrea, Cassano and M.T. Fujii (basionym: Laurencia marilzae) originally described from Spain. Additionally, the chemical profiles of previously explored species Laurencia flexuosa Kützing and Laurencia glomerata Kützing were re-investigated. The organic extracts of the above species afforded 31 compounds belonging to a wide array of structural classes including halo-chamigranes, linear C15 acetogenins, indole alkaloids, cuparanes and cyclic bromo-ethers. A new tri-cyclic keto-cuparane (4.4) was isolated from L.cf. corymbosa alongside the new cuparanes 4.1 and 4.7. Algoane (5.9), a unique marker compound isolated from L. natalensis, was previously only reported from a sea-hare. Such marker compounds which are exclusive to an individual algal species increase the ease of their subsequent identification. The feasibility of chemotaxonomy as an additional tool to classify Laurencia spp. Was established as broad predictions of a specimen’s phylogeny, based on representatives of its secondary metabolome, proved viable. The study specimens were shown to possess similar chemical profiles to their sister species e.g. L. complanata, L. sodwaniensis and L. multiclavata produced similar metabolites to their sister species as inferred by an rbcL phylogeny tree. Finally, a 1H NMR profiling study on the crude organic extracts of various Laurencia spp. generated distinctive, reproducible spectra, exposing the value of NMR spectroscopy as a rudimentary species discernment tool.
- Full Text:
- Date Issued: 2015
- Authors: Fakee, Jameel
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64696 , vital:28593
- Description: Bioprospection of marine organisms as a potential source for lead drugs is becoming increasingly popular. The secondary metabolome of these organisms consists of structurally diverse molecules possessing unprecedented carbon skeletons, the biosynthesis of which occurs via complex metabolomic pathways driven by specialist enzymes. This structural novelty is highly influential on the favourable bioactivity these compounds display. A prominent example of such a compound is trabectedin marketed as Yondelis®. Registered for the treatment of soft tissue sarcomas, this marine drug was developed from extracts of the tunicate Ecteinascidia turbinata. South Africa is renowned for possessing a highly diverse marine biota including several endemic species of marine red algae belonging to the Laurencia sensu stricto genus, which falls within the Laurencia complex. Despite having a good reputation for fascinating secondary metabolites, the taxonomy of Laurencia natural products is proving challenging for reasons including the presence of cryptic species, as well as individual species displaying morphological variability. The aim of this study was thus to isolate secondary metabolites from various South African Laurencia spp. and subsequently assess their chemotaxonomic significance by analysis of a parallel plastid rbcL phylogeny study of Laurencia spp. This study reports the first phycochemical investigation into Laurencia natalensis Kylin, Laurencia cf. corymbosa J.Agardh, Laurencia complanata (Suhr) Kützing, Laurencia sodwaniensis Francis, Bolton, Mattio and Anderson submitted, Laurencia multiclavata Francis, Bolton, Mattio and Anderson submitted, and a South African specimen of Laurenciella marilzae Gil-Rodríguez, Sentíes, Díaz-Larrea, Cassano and M.T. Fujii (basionym: Laurencia marilzae) originally described from Spain. Additionally, the chemical profiles of previously explored species Laurencia flexuosa Kützing and Laurencia glomerata Kützing were re-investigated. The organic extracts of the above species afforded 31 compounds belonging to a wide array of structural classes including halo-chamigranes, linear C15 acetogenins, indole alkaloids, cuparanes and cyclic bromo-ethers. A new tri-cyclic keto-cuparane (4.4) was isolated from L.cf. corymbosa alongside the new cuparanes 4.1 and 4.7. Algoane (5.9), a unique marker compound isolated from L. natalensis, was previously only reported from a sea-hare. Such marker compounds which are exclusive to an individual algal species increase the ease of their subsequent identification. The feasibility of chemotaxonomy as an additional tool to classify Laurencia spp. Was established as broad predictions of a specimen’s phylogeny, based on representatives of its secondary metabolome, proved viable. The study specimens were shown to possess similar chemical profiles to their sister species e.g. L. complanata, L. sodwaniensis and L. multiclavata produced similar metabolites to their sister species as inferred by an rbcL phylogeny tree. Finally, a 1H NMR profiling study on the crude organic extracts of various Laurencia spp. generated distinctive, reproducible spectra, exposing the value of NMR spectroscopy as a rudimentary species discernment tool.
- Full Text:
- Date Issued: 2015
The isolation, quantification and synthetic modification of antiplasmodial natural products from sargassum heterophyllum
- Authors: Munedzimwe, Tatenda Carol
- Date: 2012
- Subjects: Malaria -- Developing countries -- Prevention , Antimalarials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3871 , http://hdl.handle.net/10962/d1018252
- Description: Malaria is one of the most deadly parasitic diseases known to man. Although the number of malaria cases reported each year is decreasing, this disease continues to pose health and economic problems mainly in developing countries. Significant progress has been made in the fight against this disease. This includes the discovery and development of potent antimalarial agents. However, the development of resistance to most of these potent antimalarials has made the development of new antiplasmodial agents of paramount importance. Several promising antiplasmodial agents have been found from the marine environment. Amongst these are the tetraprenylated toluquinols from the brown alga: Sargassum heterophyllum. These metabolites have been reported to exhibit a range of antiplasmodial activity; however, the mechanisms by which these compounds bring about their antiplasmodial activity and the pharmacophoric groups responsible for such activity are unknown. Two species of Sargassum algae were encountered during the course of this project. From the investigation of the geographical and seasonal variation of metabolites of S. heterophyllum and S. elegans we established that there were no significant intra and inter site variations amongst metabolite profiles of both species both within and between the sampled seasons. These results enabled us to establish that the collection of both species from three different sites on the eastern coast of South Africa namely; Kenton on Sea, Port Alfred and Noordhoek in autumn, winter or spring would qualitatively yield the same metabolites. A comparison of metabolite profiles of both species also revealed no qualitative differences between metabolites of S. heterophyllum and S. elegans. The quantities of selected prenylated metabolites extracted from S. heterophyllum using four different extraction techniques was also assessed using qNMR as the method of quantification. This led to the identification of optimal extraction techniques and conditions for the extraction of sargahydroquinoic acid (1.38), sargaquinoic aid (1.39) and sargachromenol (2.10) from S. heterophyllum. From this study, the extraction of algae by soxhlet extraction using EtOH as the extraction solvent led to the extraction of the highest quantities of sargahydroquinoic acid. The potential of other extraction techniques such as microwave assisted extraction, to yield high quantities of the selected metabolites were also identified. With gram quantities of sargahydroquinoic acid (1.38) in hand, this compound was modified by oxidation, reduction, acetylation, methylation and cyclization reactions to yield nine derivatives. The derivatives and four naturally occurring prenylated toluquinols were assessed for antiplasmodial and cytotoxic activity against the FCR-3 Gambian Chloroquine resistant strain of P. falciparum and the MDA-MB-231 breast carcinoma cell line respectively. Comparison of antiplasmodial data for all twelve compounds showed that the hydroquinone moeity of sargahydroquinoic acid (1.38) is important for antiplasmodial activity while esterification of the carboxylic acid group in 1.38 resulted in more potent antiplasmodial compounds. Of all twelve compounds, compound 5.2, the hydroquinone methyl ester of 1.38 was found to be the most potent antiplasmodial compound with an IC₅₀ value of 1.94 μM and a selectivity index of 22.68.
- Full Text:
- Date Issued: 2012
- Authors: Munedzimwe, Tatenda Carol
- Date: 2012
- Subjects: Malaria -- Developing countries -- Prevention , Antimalarials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3871 , http://hdl.handle.net/10962/d1018252
- Description: Malaria is one of the most deadly parasitic diseases known to man. Although the number of malaria cases reported each year is decreasing, this disease continues to pose health and economic problems mainly in developing countries. Significant progress has been made in the fight against this disease. This includes the discovery and development of potent antimalarial agents. However, the development of resistance to most of these potent antimalarials has made the development of new antiplasmodial agents of paramount importance. Several promising antiplasmodial agents have been found from the marine environment. Amongst these are the tetraprenylated toluquinols from the brown alga: Sargassum heterophyllum. These metabolites have been reported to exhibit a range of antiplasmodial activity; however, the mechanisms by which these compounds bring about their antiplasmodial activity and the pharmacophoric groups responsible for such activity are unknown. Two species of Sargassum algae were encountered during the course of this project. From the investigation of the geographical and seasonal variation of metabolites of S. heterophyllum and S. elegans we established that there were no significant intra and inter site variations amongst metabolite profiles of both species both within and between the sampled seasons. These results enabled us to establish that the collection of both species from three different sites on the eastern coast of South Africa namely; Kenton on Sea, Port Alfred and Noordhoek in autumn, winter or spring would qualitatively yield the same metabolites. A comparison of metabolite profiles of both species also revealed no qualitative differences between metabolites of S. heterophyllum and S. elegans. The quantities of selected prenylated metabolites extracted from S. heterophyllum using four different extraction techniques was also assessed using qNMR as the method of quantification. This led to the identification of optimal extraction techniques and conditions for the extraction of sargahydroquinoic acid (1.38), sargaquinoic aid (1.39) and sargachromenol (2.10) from S. heterophyllum. From this study, the extraction of algae by soxhlet extraction using EtOH as the extraction solvent led to the extraction of the highest quantities of sargahydroquinoic acid. The potential of other extraction techniques such as microwave assisted extraction, to yield high quantities of the selected metabolites were also identified. With gram quantities of sargahydroquinoic acid (1.38) in hand, this compound was modified by oxidation, reduction, acetylation, methylation and cyclization reactions to yield nine derivatives. The derivatives and four naturally occurring prenylated toluquinols were assessed for antiplasmodial and cytotoxic activity against the FCR-3 Gambian Chloroquine resistant strain of P. falciparum and the MDA-MB-231 breast carcinoma cell line respectively. Comparison of antiplasmodial data for all twelve compounds showed that the hydroquinone moeity of sargahydroquinoic acid (1.38) is important for antiplasmodial activity while esterification of the carboxylic acid group in 1.38 resulted in more potent antiplasmodial compounds. Of all twelve compounds, compound 5.2, the hydroquinone methyl ester of 1.38 was found to be the most potent antiplasmodial compound with an IC₅₀ value of 1.94 μM and a selectivity index of 22.68.
- Full Text:
- Date Issued: 2012
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