Phytoplankton of the Southern Agulhas Large Marine Ecosystem (sACLME)
- Authors: Sonnekus, Martinus Jakobus
- Date: 2020
- Subjects: Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47646 , vital:40261
- Description: The southern Agulhas Large Marine Ecosystem (sACLME) consists of the greater Agulhas Current system, including the areas influenced by the Agulhas Current, the Agulhas Shelf, Agulhas Bank, Agulhas Retroflection as well as the Agulhas Return Current. Four biogeographical regions were identified within the sACLME and the composition of the phytoplankton communities and the associated physico-chemical variables in each were investigated. Water temperature and nitrate concentration were found to be the main drivers of the sACLME phytoplankton community. A total of 215 phytoplankton taxa were identified that were separated into two groups: the Agulhas Current group and the Southwest Indian Ocean Ridge group. The structure of the phytoplankton community was consistently homogeneous throughout the sACLME. Nutrient concentrations of the water varied, but nitrate was the most abundant source of nitrogen, especially in regions that were subjected to the upwelling of cold nutrient-rich water. The phytoplankton communities were significantly influenced by the availability and stoichiometry of the macronutrients nitrogen; phosphorus and silicon. The low mean N:P ratio of 5.5 is an indication that the waters of the sACLME are generally nitrogen limited, as is typical of oceanic systems. There is a change in phytoplankton cell size and functional groups within in the various water masses that are specific to certain biogeographical regions within the Agulhas Current system. It is clear that frontal systems may form barriers between phytoplankton communities.
- Full Text:
- Date Issued: 2020
- Authors: Sonnekus, Martinus Jakobus
- Date: 2020
- Subjects: Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47646 , vital:40261
- Description: The southern Agulhas Large Marine Ecosystem (sACLME) consists of the greater Agulhas Current system, including the areas influenced by the Agulhas Current, the Agulhas Shelf, Agulhas Bank, Agulhas Retroflection as well as the Agulhas Return Current. Four biogeographical regions were identified within the sACLME and the composition of the phytoplankton communities and the associated physico-chemical variables in each were investigated. Water temperature and nitrate concentration were found to be the main drivers of the sACLME phytoplankton community. A total of 215 phytoplankton taxa were identified that were separated into two groups: the Agulhas Current group and the Southwest Indian Ocean Ridge group. The structure of the phytoplankton community was consistently homogeneous throughout the sACLME. Nutrient concentrations of the water varied, but nitrate was the most abundant source of nitrogen, especially in regions that were subjected to the upwelling of cold nutrient-rich water. The phytoplankton communities were significantly influenced by the availability and stoichiometry of the macronutrients nitrogen; phosphorus and silicon. The low mean N:P ratio of 5.5 is an indication that the waters of the sACLME are generally nitrogen limited, as is typical of oceanic systems. There is a change in phytoplankton cell size and functional groups within in the various water masses that are specific to certain biogeographical regions within the Agulhas Current system. It is clear that frontal systems may form barriers between phytoplankton communities.
- Full Text:
- Date Issued: 2020
Antimalarial secondary metabolites from Morinda lucida
- Authors: Chithambo, Bertha
- Date: 2017
- Subjects: Botanical chemistry , Anthraquinones , Antimalarials , Rubiaceae -- Therapeutic use , Malaria -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/45730 , vital:25535
- Description: Antimalarial activities of secondary metabolites from Morinda lucida (Rubiaceae), were investigated. Even though M. lucida is traditionally used to treat malaria, diabetes, jaundice, hypertension, dysentery and many other diseases, the compounds in this plant have not yet been fully investigated and characterised. Most of the studies that have been done on this plant focused on the medicinal properties of the crude extracts but have not gone further to isolate and characterise the compounds. In this study, the methanol - dichloromethane crude extract from the bark of M. lucida was fractionated into fractions 1-8. Fractions 2-5 were purified in order to isolate active secondary metabolites. The isolated pure compounds were characterised and identified. An in vitro antimalarial assay was carried out on the crude extract, fractions, pure compounds and solutions made from different combinations of pure compounds using the parasite lactate dehydrogenase (pLDH) assay. An IC50 done on the methanolic crude extract gave a value of 25 µg/mL. The % cell viability for the crude extract in cell toxicity assay remained at 100%. Each of the pure compounds tested had very little activity. Their activities were increased when samples from the different compounds were mixed. One of these mixtures reduced malaria viability to about 22 % at 20 µM and gave an IC50 value of 17 µM. Antibacterial assays were also carried out on the crude extract and fractions. Fractions 2 and 3 were relatively active (MIC values ranging between 125-1000 µg/mL) against M. cattarhalis and E. faecalis. Fraction 2 was also the most active on S. typhimurium and S. aureus (MIC value of 1000 µg/mL) compared with the other fractions. This same fraction also showed some activity against M. tuberculosis with MIC90 and MIC99 values of 40.9 and 46.3 µg/mL respectively in an anti-tuberculosis assay.The following compounds, comprising of iridoids (asperuloside and asperulosidic acid), terpenoids (stigmasterol, P-sitosterol, campesterol, lanosterol and cycloartenol) and anthraquinones [5,15-O-dimethylmorindol, 1,7-dihydroxy-2-methoxy-5-(methoxymethyl) anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone], were isolated. All these compounds have been isolated from different plants before with the exception of 1,7-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone which were tentatively assigned the structures due to insufficient data. To the best of our knowledge, this is the first report on the identification of all of the mentioned compounds, with the exception of ß-sitosterol and stigmasterol, from M. lucida. Molecular docking was performed on one of the isolated anthraquinones (5,15-O- dimethylmorindol) to check if it can bind to cytochrome bci, a known target for atovaquone. This compound interacted with the same amino acids that atovaquone, a well known antimalarial agent, interacted with on cytochrome bc1 indicating a possible similar mode of action.
- Full Text:
- Date Issued: 2017
- Authors: Chithambo, Bertha
- Date: 2017
- Subjects: Botanical chemistry , Anthraquinones , Antimalarials , Rubiaceae -- Therapeutic use , Malaria -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/45730 , vital:25535
- Description: Antimalarial activities of secondary metabolites from Morinda lucida (Rubiaceae), were investigated. Even though M. lucida is traditionally used to treat malaria, diabetes, jaundice, hypertension, dysentery and many other diseases, the compounds in this plant have not yet been fully investigated and characterised. Most of the studies that have been done on this plant focused on the medicinal properties of the crude extracts but have not gone further to isolate and characterise the compounds. In this study, the methanol - dichloromethane crude extract from the bark of M. lucida was fractionated into fractions 1-8. Fractions 2-5 were purified in order to isolate active secondary metabolites. The isolated pure compounds were characterised and identified. An in vitro antimalarial assay was carried out on the crude extract, fractions, pure compounds and solutions made from different combinations of pure compounds using the parasite lactate dehydrogenase (pLDH) assay. An IC50 done on the methanolic crude extract gave a value of 25 µg/mL. The % cell viability for the crude extract in cell toxicity assay remained at 100%. Each of the pure compounds tested had very little activity. Their activities were increased when samples from the different compounds were mixed. One of these mixtures reduced malaria viability to about 22 % at 20 µM and gave an IC50 value of 17 µM. Antibacterial assays were also carried out on the crude extract and fractions. Fractions 2 and 3 were relatively active (MIC values ranging between 125-1000 µg/mL) against M. cattarhalis and E. faecalis. Fraction 2 was also the most active on S. typhimurium and S. aureus (MIC value of 1000 µg/mL) compared with the other fractions. This same fraction also showed some activity against M. tuberculosis with MIC90 and MIC99 values of 40.9 and 46.3 µg/mL respectively in an anti-tuberculosis assay.The following compounds, comprising of iridoids (asperuloside and asperulosidic acid), terpenoids (stigmasterol, P-sitosterol, campesterol, lanosterol and cycloartenol) and anthraquinones [5,15-O-dimethylmorindol, 1,7-dihydroxy-2-methoxy-5-(methoxymethyl) anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone], were isolated. All these compounds have been isolated from different plants before with the exception of 1,7-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone which were tentatively assigned the structures due to insufficient data. To the best of our knowledge, this is the first report on the identification of all of the mentioned compounds, with the exception of ß-sitosterol and stigmasterol, from M. lucida. Molecular docking was performed on one of the isolated anthraquinones (5,15-O- dimethylmorindol) to check if it can bind to cytochrome bci, a known target for atovaquone. This compound interacted with the same amino acids that atovaquone, a well known antimalarial agent, interacted with on cytochrome bc1 indicating a possible similar mode of action.
- Full Text:
- Date Issued: 2017
Characterisation, antimalarial and biological activities of secondary metabolites from leaves of anonidium mannii
- Authors: Makoni, Pfungwa Gervase
- Date: 2017
- Subjects: Anonidium mannii -- Therapeutic use , Botanical chemistry , Annonaceae -- Therapeutic use , Apocynaceae -- Therapeutic use , Malaria -- Chemotherapy , Tuberculosis -- Chemotherapy , Bacterial diseases -- Chemotherapy , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4797 , vital:20725
- Description: Anonidium mannii is a plant of the Annonaceae genus which is used traditionally in Africa for the treatment of gonorrhoea, malaria, cancer, skin inflammation and dysentery. In this study we will evaluate antimalarial, antifungal, anti - tuberculosis, antibacterial activities and cytotoxicity of different fractions in order to provide a scientific rationale for the traditional use of Anonidium mannii as well as provide possible novel drugs in the treatment of multi drug resistant strains of parasites and bacteria. Extracts from dried leaves were obtained by using solvent extraction and different fractions obtained using column chromatography eluted with solvents of varying polarities to obtain a wide range of metabolites. The antimalarial activity of the various fractions and some pure compounds was evaluated using plasmodium lactate dehydrogenase (pLDH) assay. Cytotoxicity was evaluated using HeLa cells while anti – tuberculosis assay was evaluated using the green fluorescent protein. Antibacterial activity of the extracts was evaluated using micro-dilution assay against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria and Gram-negative (Escherichia coli and Salmonella typhi) bacteria. Antifungal activity was evaluated against Candida albicans. The antimalarial assays yielded some fractions with promising IC50 values. The selected fractions yielded activities ranging between 0.73 μg/mL and 20.23 μg/mL. The fraction with the best activity was obtained from a hexane/ethyl acetate fraction. AM1C, a cholestane, showed the best activity from the pure metabolites that were screened. AM3C, stigmasterol, a pure compound gave the best antifungal activity with an MIC of 0.063 μg/mL. AM9C another pure compound (sterol) showed the best activity against S. typhi with a value of 0.031 μg/mL. AM2C a pure compound showed an activity of 0.063 μg/mL against E. faecalis. The best cytotoxicity was demonstrated by the fraction C2AM3P with a cell viability of 7.1 ± 0.2 % while AM1C had a viability of 20.2 ± 1.2 %. Several pure metabolites were isolated and four of these were positively identified as steroids. Of these steroids the structure of three novel metabolites from A. mannii was deduced. The study showed promising antibacterial, antifungal, anti – tuberculosis, antimalarial and anticancer activity of A. mannii. These results validate the use of A. manni against cancer, skin inflammation which is caused by fungus, malaria and bacterial diseases.
- Full Text:
- Date Issued: 2017
- Authors: Makoni, Pfungwa Gervase
- Date: 2017
- Subjects: Anonidium mannii -- Therapeutic use , Botanical chemistry , Annonaceae -- Therapeutic use , Apocynaceae -- Therapeutic use , Malaria -- Chemotherapy , Tuberculosis -- Chemotherapy , Bacterial diseases -- Chemotherapy , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4797 , vital:20725
- Description: Anonidium mannii is a plant of the Annonaceae genus which is used traditionally in Africa for the treatment of gonorrhoea, malaria, cancer, skin inflammation and dysentery. In this study we will evaluate antimalarial, antifungal, anti - tuberculosis, antibacterial activities and cytotoxicity of different fractions in order to provide a scientific rationale for the traditional use of Anonidium mannii as well as provide possible novel drugs in the treatment of multi drug resistant strains of parasites and bacteria. Extracts from dried leaves were obtained by using solvent extraction and different fractions obtained using column chromatography eluted with solvents of varying polarities to obtain a wide range of metabolites. The antimalarial activity of the various fractions and some pure compounds was evaluated using plasmodium lactate dehydrogenase (pLDH) assay. Cytotoxicity was evaluated using HeLa cells while anti – tuberculosis assay was evaluated using the green fluorescent protein. Antibacterial activity of the extracts was evaluated using micro-dilution assay against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria and Gram-negative (Escherichia coli and Salmonella typhi) bacteria. Antifungal activity was evaluated against Candida albicans. The antimalarial assays yielded some fractions with promising IC50 values. The selected fractions yielded activities ranging between 0.73 μg/mL and 20.23 μg/mL. The fraction with the best activity was obtained from a hexane/ethyl acetate fraction. AM1C, a cholestane, showed the best activity from the pure metabolites that were screened. AM3C, stigmasterol, a pure compound gave the best antifungal activity with an MIC of 0.063 μg/mL. AM9C another pure compound (sterol) showed the best activity against S. typhi with a value of 0.031 μg/mL. AM2C a pure compound showed an activity of 0.063 μg/mL against E. faecalis. The best cytotoxicity was demonstrated by the fraction C2AM3P with a cell viability of 7.1 ± 0.2 % while AM1C had a viability of 20.2 ± 1.2 %. Several pure metabolites were isolated and four of these were positively identified as steroids. Of these steroids the structure of three novel metabolites from A. mannii was deduced. The study showed promising antibacterial, antifungal, anti – tuberculosis, antimalarial and anticancer activity of A. mannii. These results validate the use of A. manni against cancer, skin inflammation which is caused by fungus, malaria and bacterial diseases.
- Full Text:
- Date Issued: 2017
Isolation of xylanolytic multi-enzyme complexes from Bacillus subtilis SJ01
- Authors: Jones, Sarah Melissa Jane
- Date: 2010
- Subjects: Bacillus subtilis , Xylans , Multienzyme complexes , Botanical chemistry , Cellulose , Hemicellulose , Polysaccharides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3974 , http://hdl.handle.net/10962/d1004033 , Bacillus subtilis , Xylans , Multienzyme complexes , Botanical chemistry , Cellulose , Hemicellulose , Polysaccharides
- Description: Cellulose and hemicellulose account for a large portion of the world‘s plant biomass. In nature, these polysaccharides are intertwined forming complex materials that require multiple enzymes to degrade them. Multi-enzyme complexes (MECs) consist of a number of enzymes working in close proximity and synergistically to degrade complex substrates with higher efficiency than individual enzymes. The cellulosome is a cellulolytic MEC produced by anaerobic bacteria that has been studied extensively since its discovery in 1983. The aim of this study was to purify a cellulolytic and/or hemicellulolytic MEC from an aerobic bacterium of the Bacillus genus. Several bacterial isolates were identified using morphological characteristics and 16S rDNA sequencing, and screened for their ability to degrade cellulose and xylan using a MEC. The isolate that produced a high molecular weight protein fraction with the greatest ability to degrade Avicel®, carboxymethyl cellulose (CMC) and birchwood xylan was identified as Bacillus subtilis SJ01. An optimised growth medium, consisting of vitamins, trace elements, birchwood xylan (as the carbon source), and yeast and ammonium sulphate (as the nitrogen sources), increased the production of CMCase and xylanase enzymes from this bacterium. The removal of a competing bacterial strain from the culture and the inhibition of proteases also increased enzyme activities. A growth curve of B. subtilis SJ01 indicated that xylanase production was highest in early stationary growth phase and thus 84 hours was chosen as the best cell harvesting time. To purify the MECs produced by B. subtilis SJ01 size-exclusion chromatography on a Sephacryl S-400 column was used. It was concluded that (for the purposes of this study) the best method of concentrating the culture supernatant prior to loading onto Sephacryl S-400 was the use of ultrafiltration with a 50 kDa cut-off membrane. Two MECs, named C1 and C2 of 371 and 267 kDa, respectively, were purified from the culture supernatant of B. subtilis SJ01. Electrophoretic analysis revealed that these MECs consisted of 16 and 18 subunits, respectively, 4 of which degraded birchwood xylan and 5 of which degraded oat spelt xylan. The MECs degraded xylan substrates (C1: 0.24 U/mg, C2: 0.14 U/mg birchwood xylan) with higher efficiency than cellulose substrates (C1: 0.002 U/mg, C2: 0.01 U/mg CMC), and could therefore be considered xylanosomes. Interestingly, the MECs did not bind to insoluble birchwood xylan or Avicel® and did not contain glycosylated proteins, which are common features of cellulosomes. This study is, therefore, important in revealing the presence of MECs that differ from the cellulosome and that may have particular application in industries requiring high xylanase activity, such as the paper and pulp industry. The abundant genetic information available on B. subtilis means that this organism could also be used for genetic engineering of cellulolytic/hemicellulolytic MECs.
- Full Text:
- Date Issued: 2010
- Authors: Jones, Sarah Melissa Jane
- Date: 2010
- Subjects: Bacillus subtilis , Xylans , Multienzyme complexes , Botanical chemistry , Cellulose , Hemicellulose , Polysaccharides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3974 , http://hdl.handle.net/10962/d1004033 , Bacillus subtilis , Xylans , Multienzyme complexes , Botanical chemistry , Cellulose , Hemicellulose , Polysaccharides
- Description: Cellulose and hemicellulose account for a large portion of the world‘s plant biomass. In nature, these polysaccharides are intertwined forming complex materials that require multiple enzymes to degrade them. Multi-enzyme complexes (MECs) consist of a number of enzymes working in close proximity and synergistically to degrade complex substrates with higher efficiency than individual enzymes. The cellulosome is a cellulolytic MEC produced by anaerobic bacteria that has been studied extensively since its discovery in 1983. The aim of this study was to purify a cellulolytic and/or hemicellulolytic MEC from an aerobic bacterium of the Bacillus genus. Several bacterial isolates were identified using morphological characteristics and 16S rDNA sequencing, and screened for their ability to degrade cellulose and xylan using a MEC. The isolate that produced a high molecular weight protein fraction with the greatest ability to degrade Avicel®, carboxymethyl cellulose (CMC) and birchwood xylan was identified as Bacillus subtilis SJ01. An optimised growth medium, consisting of vitamins, trace elements, birchwood xylan (as the carbon source), and yeast and ammonium sulphate (as the nitrogen sources), increased the production of CMCase and xylanase enzymes from this bacterium. The removal of a competing bacterial strain from the culture and the inhibition of proteases also increased enzyme activities. A growth curve of B. subtilis SJ01 indicated that xylanase production was highest in early stationary growth phase and thus 84 hours was chosen as the best cell harvesting time. To purify the MECs produced by B. subtilis SJ01 size-exclusion chromatography on a Sephacryl S-400 column was used. It was concluded that (for the purposes of this study) the best method of concentrating the culture supernatant prior to loading onto Sephacryl S-400 was the use of ultrafiltration with a 50 kDa cut-off membrane. Two MECs, named C1 and C2 of 371 and 267 kDa, respectively, were purified from the culture supernatant of B. subtilis SJ01. Electrophoretic analysis revealed that these MECs consisted of 16 and 18 subunits, respectively, 4 of which degraded birchwood xylan and 5 of which degraded oat spelt xylan. The MECs degraded xylan substrates (C1: 0.24 U/mg, C2: 0.14 U/mg birchwood xylan) with higher efficiency than cellulose substrates (C1: 0.002 U/mg, C2: 0.01 U/mg CMC), and could therefore be considered xylanosomes. Interestingly, the MECs did not bind to insoluble birchwood xylan or Avicel® and did not contain glycosylated proteins, which are common features of cellulosomes. This study is, therefore, important in revealing the presence of MECs that differ from the cellulosome and that may have particular application in industries requiring high xylanase activity, such as the paper and pulp industry. The abundant genetic information available on B. subtilis means that this organism could also be used for genetic engineering of cellulolytic/hemicellulolytic MECs.
- Full Text:
- Date Issued: 2010
A study of the alkaloid content of the Senecio speciosus/Macrocephalus complex
- Authors: Grue, Margaret Ruth
- Date: 1992
- Subjects: Alkaloids -- Research , Pyrrolizidines -- Research , Botanical chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4362 , http://hdl.handle.net/10962/d1005027 , Alkaloids -- Research , Pyrrolizidines -- Research , Botanical chemistry
- Description: The isolation and identification of pyrrolizidine alkaloids from various plant species from 1988 to May 1991 are reviewed and the alkaloids of two indigenous plant species, Senecio speciosus Willd and Senecio macrocephalus DC, were investigated. A brief review of the methods used for isolation and identification of pyrrolizidines is also given. S. speciosus was found to contain two new alkaloids, 7-senecioyl-9-sarracinylheliotridine and 7-isosarracinyl-9- sarracinyl-heliotridine, which were identified using highfield NMR techniques. A number of other alkaloids were tentatively identified using GC-MS. S. macrocephalus contains very little alkaloid, but a number of pyrrolizidine alkaloids were tentatively identified using GC-MS. Standard alkaloids for GC-MS work were obtained both by extraction from a number of plant species and by synthesis of simple monoester alkaloids. In this process the alkaloid neosarracine, previously described by GC-MS, was isolated and NMR data for this compound are reported for the first time. S. speciosus and S. macrocephalus are morphologically very similar and their counterparts in the Grahamstown district exhibit features characteristic of both species. This could be due to hybridization, genetic mutation or simple variation within the species. The alkaloids of four local plant populations were examined in order to collect taxonomic markers whereby it was hoped that the Grahamstown plants could be satisfactorily classified. Three of the plant populations were found to contain 7-senecioyl-9-sarracinylheliotridine and 7-angelyl-9-sarracinyl-heliotridine. One population was found to contain the known alkaloid retrorsine along with the new alkaloid 2-hydroxy-l, 2-dihydrosenkirkine. The alkaloidal fractions of all four populations were compared using GC-MS and NMR techniques. Tentative taxonomic conclusions were drawn.
- Full Text:
- Date Issued: 1992
- Authors: Grue, Margaret Ruth
- Date: 1992
- Subjects: Alkaloids -- Research , Pyrrolizidines -- Research , Botanical chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4362 , http://hdl.handle.net/10962/d1005027 , Alkaloids -- Research , Pyrrolizidines -- Research , Botanical chemistry
- Description: The isolation and identification of pyrrolizidine alkaloids from various plant species from 1988 to May 1991 are reviewed and the alkaloids of two indigenous plant species, Senecio speciosus Willd and Senecio macrocephalus DC, were investigated. A brief review of the methods used for isolation and identification of pyrrolizidines is also given. S. speciosus was found to contain two new alkaloids, 7-senecioyl-9-sarracinylheliotridine and 7-isosarracinyl-9- sarracinyl-heliotridine, which were identified using highfield NMR techniques. A number of other alkaloids were tentatively identified using GC-MS. S. macrocephalus contains very little alkaloid, but a number of pyrrolizidine alkaloids were tentatively identified using GC-MS. Standard alkaloids for GC-MS work were obtained both by extraction from a number of plant species and by synthesis of simple monoester alkaloids. In this process the alkaloid neosarracine, previously described by GC-MS, was isolated and NMR data for this compound are reported for the first time. S. speciosus and S. macrocephalus are morphologically very similar and their counterparts in the Grahamstown district exhibit features characteristic of both species. This could be due to hybridization, genetic mutation or simple variation within the species. The alkaloids of four local plant populations were examined in order to collect taxonomic markers whereby it was hoped that the Grahamstown plants could be satisfactorily classified. Three of the plant populations were found to contain 7-senecioyl-9-sarracinylheliotridine and 7-angelyl-9-sarracinyl-heliotridine. One population was found to contain the known alkaloid retrorsine along with the new alkaloid 2-hydroxy-l, 2-dihydrosenkirkine. The alkaloidal fractions of all four populations were compared using GC-MS and NMR techniques. Tentative taxonomic conclusions were drawn.
- Full Text:
- Date Issued: 1992
Photosynthetic gas exchange responses to light, temperature, carbon dioxide and water stress, and changes in photosynthetic pigments to light and water stress in two cultivars of Hordeum vulgare L
- Logie, Malcolme Ronald Ruxton
- Authors: Logie, Malcolme Ronald Ruxton
- Date: 1992
- Subjects: Plants -- Photorespiration , Plants -- Transpiration , Botanical chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4210 , http://hdl.handle.net/10962/d1003779
- Description: The gas exchange responses of two cultivars of Hordeum vulgare L., to light, temperature, CO₂ and water stress were investigated in the laboratory. The optimum temperature for net CO₂ assimilation was found to be 25°C and 22.5°C for cv. Clipper and cv. Dayan respectively. Net CO₂ assimilation was reduced at 30°C in cv. Dayan. At low light intensity the highest quantum yield efficiency was 0.051 mol.mol⁻¹ at 30°C for cv. Clipper, and 0.066 mol.mol⁻¹ at 20°C for cv. Dayan. At the same temperature, cv. Clipper had a higher water use efficiency than cv. Dayan, but stomatal conductance for cv. Dayan was higher than cv. Clipper. Stomatal limitation to CO₂ was lowest at the optimum temperature for CO₂ assimilation in both cultivars. Stomata limited CO₂ assimilation in cv. Clipper to a larger degree than in cv. Dayan. Relative stomatal limitation for cv. Clipper at 25°C was 0.280 ± 0.010, and for cv. Dayan at 22.5°C was 0.028 ± 0.011. Short-term exposure to elevated CO₂ concentrations increased CO₂ assimilation in both cultivars, but more so for cv. Clipper. Transpiration rate at elevated CO₂ partial pressures were higher in cv. Dayan than in cv. Clipper. At very high CO₂ (860 μmol.m⁻²s⁻¹) partial pressure water use efficiency in cv. Clipper was higher than cv. Dayan, but at low CO₂ partial pressures water use efficiency in cv. Dayan was higher than cv. Clipper. Water stress reduced the relative leaf water content and net CO₂ assimilation in both cultivars. Cultivar Dayan was more tolerant to water stress, and CO₂ assimilation in this cultivar was less affected by water stress. In both cultivars water stress increased the concentration of chlorophyll a, chlorophyll b, and chlorophyll a+b. The chlorophyll a:b ratio remained relatively constant throughout the stress period. No correlation between relative leaf water content and total carotenoid concentration was observed.
- Full Text:
- Date Issued: 1992
- Authors: Logie, Malcolme Ronald Ruxton
- Date: 1992
- Subjects: Plants -- Photorespiration , Plants -- Transpiration , Botanical chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4210 , http://hdl.handle.net/10962/d1003779
- Description: The gas exchange responses of two cultivars of Hordeum vulgare L., to light, temperature, CO₂ and water stress were investigated in the laboratory. The optimum temperature for net CO₂ assimilation was found to be 25°C and 22.5°C for cv. Clipper and cv. Dayan respectively. Net CO₂ assimilation was reduced at 30°C in cv. Dayan. At low light intensity the highest quantum yield efficiency was 0.051 mol.mol⁻¹ at 30°C for cv. Clipper, and 0.066 mol.mol⁻¹ at 20°C for cv. Dayan. At the same temperature, cv. Clipper had a higher water use efficiency than cv. Dayan, but stomatal conductance for cv. Dayan was higher than cv. Clipper. Stomatal limitation to CO₂ was lowest at the optimum temperature for CO₂ assimilation in both cultivars. Stomata limited CO₂ assimilation in cv. Clipper to a larger degree than in cv. Dayan. Relative stomatal limitation for cv. Clipper at 25°C was 0.280 ± 0.010, and for cv. Dayan at 22.5°C was 0.028 ± 0.011. Short-term exposure to elevated CO₂ concentrations increased CO₂ assimilation in both cultivars, but more so for cv. Clipper. Transpiration rate at elevated CO₂ partial pressures were higher in cv. Dayan than in cv. Clipper. At very high CO₂ (860 μmol.m⁻²s⁻¹) partial pressure water use efficiency in cv. Clipper was higher than cv. Dayan, but at low CO₂ partial pressures water use efficiency in cv. Dayan was higher than cv. Clipper. Water stress reduced the relative leaf water content and net CO₂ assimilation in both cultivars. Cultivar Dayan was more tolerant to water stress, and CO₂ assimilation in this cultivar was less affected by water stress. In both cultivars water stress increased the concentration of chlorophyll a, chlorophyll b, and chlorophyll a+b. The chlorophyll a:b ratio remained relatively constant throughout the stress period. No correlation between relative leaf water content and total carotenoid concentration was observed.
- Full Text:
- Date Issued: 1992
An investigation into chemical and biological assays of new compounds from aloes
- Authors: Mapp, R K
- Date: 1969
- Subjects: Medicinal plants -- Research -- South Africa , Botanical chemistry , Aloe -- Analysis , Aloe -- Research -- South Africa , Aloe , Aloin
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3850 , http://hdl.handle.net/10962/d1012830
- Description: The drug aloes has been known since earliest times and is mentioned in the Ebers papyrus of circa 1,500 B.C. Alexander the Great is reported to have sent a commission to Socotra to investigate the aloes grown there. The chemical composition of aloes is complex, and being of plant origin, subject to variation. Both the complexity of the chemical constituents and their biological variation has resulted in a very large volume of conflicting material being published on this drug export. Since aloes is used as a purgative for both human and veterinary use, it is obviously important that the dosage and consequently the active constituents, should comply to an accurate means of standardisation. To date, despite extensive world wide research into this drug such standardisation has not been achieved. Even the methods used for the assay of the principal constituent, aloin, vary considerably in their results, and to complicate matters new chemical principles have been isolated from aloes in recent years. Consequently the purpose of this work has been to investigate the main chemical assay methods currently in use, and to determine which was the most accurate, and why discrepancies occurred in the selected assay methods. furthermore the results obtained by chemical assay have been compared with those obtained by biological assay in an attempt to correlate aloin content with purgative activity. Newly isolated compounds have been investigated biologically for the first time, and the biological assays of the resinous, glycosidal and other compounds of aloes have been performed. Intro. p.1-2.
- Full Text:
- Date Issued: 1969
- Authors: Mapp, R K
- Date: 1969
- Subjects: Medicinal plants -- Research -- South Africa , Botanical chemistry , Aloe -- Analysis , Aloe -- Research -- South Africa , Aloe , Aloin
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3850 , http://hdl.handle.net/10962/d1012830
- Description: The drug aloes has been known since earliest times and is mentioned in the Ebers papyrus of circa 1,500 B.C. Alexander the Great is reported to have sent a commission to Socotra to investigate the aloes grown there. The chemical composition of aloes is complex, and being of plant origin, subject to variation. Both the complexity of the chemical constituents and their biological variation has resulted in a very large volume of conflicting material being published on this drug export. Since aloes is used as a purgative for both human and veterinary use, it is obviously important that the dosage and consequently the active constituents, should comply to an accurate means of standardisation. To date, despite extensive world wide research into this drug such standardisation has not been achieved. Even the methods used for the assay of the principal constituent, aloin, vary considerably in their results, and to complicate matters new chemical principles have been isolated from aloes in recent years. Consequently the purpose of this work has been to investigate the main chemical assay methods currently in use, and to determine which was the most accurate, and why discrepancies occurred in the selected assay methods. furthermore the results obtained by chemical assay have been compared with those obtained by biological assay in an attempt to correlate aloin content with purgative activity. Newly isolated compounds have been investigated biologically for the first time, and the biological assays of the resinous, glycosidal and other compounds of aloes have been performed. Intro. p.1-2.
- Full Text:
- Date Issued: 1969
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