The use of gabions as a tool for ecological engineering
- Authors: Seath, Jessica Lauren
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434987 , vital:73121
- Description: Anthropogenic activities are centred in coastal ecosystems, including the development of harbours and/or marinas. The artificial structures used in coastal development typically has a different composition, orientation and level of complexity to that of natural ecosystems contributing to loss of biodiversity and increased incidence of invasive species. Ecological engineering research is attempting to identify different types of structures and materials that can increase species diversity and target species of conservation concern in coastal systems. The aim of this study was to investigate the efficacy of gabions (rock filled structures) as an ecological engineering tool by comparing community structure on these structures with pre-existing seawall structures within a small harbour and marina in South Africa (Knysna Harbour). The objectives of the study were to compare the differences in; 1) fish and; 2) colonising organisms’ diversity and composition between two artificial structures. Thirteen gabion boxes were deployed in Knysna Harbour and together with corresponding seawalls, monitored quarterly over a period of 12 months (August 2020 – August 2021) to assess taxon and functional richness, diversity, abundance and composition of fish, invertebrate and algal species. Physico-chemical characteristics of the water body were also monitored quarterly. Remote underwater video systems were used to quantify MaxN (maximum number of a fish species in the frame at any one time during each set that gives an indication of relative abundance) and identify fish species. The results of the two-way crossed ANOVAs indicated that gabion habitats recruited greater numbers and more types of fish species and from more functional groups than the seawalls, especially omnivorous and carnivorous fish. Additionally, photoquadrats were used to quantify percentage cover, counts and to identify colonising taxa. The results of the two-way crossed ANOVAs indicated that gabions hosted greater numbers of species resulting in a higher overall diversity and abundance of colonising organisms than seawalls. By contrast, the seawalls supported more types of functional groups of colonising organisms than gabions, largely due to abundances of different algal species. The results from the crossed PERMANOVAs indicated that the composition of fish and colonising organisms were vastly different from one another, and that each habitat was supporting very different functional groups. Results indicate that whilst both gabions and seawalls contain several alien species, that the ratio of native to alien species is higher in gabion habitats. Additionally, this research observed that gabion structures hosted four species listed on the IUCN Red List of Threatened Species. This study has highlighted that the use of gabions (with their natural increased complexity) could be important to consider for the future of urban coastal development in harbours such as in Knysna Harbour. Ecological engineering projects using gabions have the potential to be used in South Africa in projects that aim at increasing biodiversity in urban coastal environments. As well as increasing the settlement and abundance of habitat-forming ecosystem engineers to ensure the long-term stability of these ecosystems. They can be used both in the development of new costal development projects as well as in an ad-hoc fashion where they can be interspersed on seawalls in harbours. Additionally, gabions have the potential to be used in projects that target species of conservation concern such as the endangered Knysna Seahorse (Hippocampus capensis). It is, however, important to monitor the invasion by non-native species in future ecological engineering projects in South Africa as well as their potential for creating ecological traps (a situation in which an organism may be convinced to settle in a low-quality habitat) for certain species. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2024
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Octa carboxy metal (II) phthalocyanine covalent films as pH sensitive electrochemical sensor for neurotransmitters
- Authors: Moyo, Iphithuli
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424525 , vital:72161
- Description: Octa acyl chloride metallophthalocyanines of cobalt (CoOAClPc) and iron (FeOAClPc) were synthesized and characterized using spectroscopic and electrochemical techniques. The metallophthalocyanines were fabricated as thin films onto phenylethylamine (PEA) pre-grafted Au electrode following a covalent amide reaction. The spectroscopic and electrochemical characterization confirmed the modification of the bare Au with PEA monolayer thin film (Au-PEA) and the covalent immobilization of MOAClPc to yield Au-PEA-MOAClPc (where M is Co and Fe). The acyl chloride functional groups were hydrolyzed forming pH sensitive thin films of terminal carboxylic acid (-COOH) functional groups (Au-PEA-MOCAPc). The Au-PEA-MOCAPc electrode exhibited pH selectivity and sensitivity properties towards the negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-MOCAPc electrodes were studied for their electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters; dopamine (DA), epinephrine (EP) and norepinephrine (NOR). The electrodes were further investigated in the screening of ascorbic and uric acids by means of pH sensitive functional groups. The modification process exhibited good reproducibility. Excellent electrocatalytic and electroanalytical properties were observed. The limits of detection (LOD) determined using 3σ/m was found to be 64 nM, 0.22 μM and 0.17 μM for DA, EP and NOR respectively using Au-PEA-CoOCAPc. For Au-PEA-FeOCAPc, the LOD was found to 0.24 μM, 0.45 μM and 0.34 μM for DA, EP and NOR respectively. The Au-PEA-MOCAPc electrodes screened off the strong interferents, ascorbic and uric acid. The Au-PEA-FeOCAPc electrode was evaluated for its potential application in real sample analysis using new born calf serum, and it showed excellent percentage recoveries. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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Pharmaco-chemical investigation of Erythrina caffra: extracts, isolated compounds and their biological activities
- Authors: Nogqala, Simnikiwe
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422459 , vital:71944
- Description: In this study, secondary metabolites isolated from Erythrina caffra, a medicinal plant indigenous to South Africa, were investigated. E. caffra is well-known for its healing properties and it is traditionally used for treating bacterial infections like tuberculosis (TB), abscesses, tooth aches and ear infections. Its extracts have also been used to treat cancer. Though many studies have been done on this plant, most of them tended to focus solely on the isolated compounds. In the present study however, extracts, fractions and isolated compounds from E. caffra were evaluated for their anticancer, anti-oxidant, anti-enzymatic, antibacterial and cytotoxicity. The methanol crude extract (B1) from the stem bark of E. caffra was used to extract alkaloidic fractions (B2 and B3) using ethyl acetate and n-butanol respectively, a third fraction (B4) was also extracted using ethyl acetate this fraction was called a neutral fraction. The neutral fraction (B4) was fractionated and through a sequence of column chromatography three active secondary metabolites were isolated. The isolated compounds included Lupeol (1), stigmasterol (2) and 5,7-Dihydroxy-4'-methoxy-3',5'-diprenylflavanone (3). These isolated compounds were characterized and identified using spectroscopic techniques including IR, NMR and high-resolution Mass Spectrometry. Using the cell line HCC-70, isolated from a primary ductal carcinoma, in vitro anticancer assays were carried out on the crude extract from the bark, fractions, isolated compounds and an unseparated mixture of two compounds. These samples were also evaluated for their anti-oxidant, anti-enzymatic, antibacterial and cytotoxicity activities. The crude extract inhibited the cell viability by over 30% and had no effect on the HeLa cells at concentrations of 20μM. Abyssinone V’ 4-methyl-ether (3) and the mixture of stigmasterol (2) and an unidentified compound exhibited potent anticancer activity against the HCC-70 cell line with IC50 of 18.05μM and 9.04μM respectively. Antibacterial assays were also carried out on the crude extracts, fractions and concoctions made from the fractions with the best activity combined with the ones that performed poorly. The concoctions were prepared as two separate series (S and N series). The crude extract inhibited more than 80% of the Staphylococcus aureus cells at a concentration of 20μM with only minimal damage to the HeLa cells. In the concoctions however, the N series managed to inhibit over 96% of the S. aureus while exhibiting no cytotoxicity towards HeLa cells. The extract and its fractions also showed good anti-oxidant activities. Molecular docking of these compounds was done on the Human estrogen receptor (PDB ID:3ERT) and Abyssinone V’ 4-methyl-ether (3) showed the best docking score of -6.6 Kcal/mol, for the simulation against Epidermal growth factor receptor (PDB ID: 1M17) Stigmasterol (2) showed the best docking score of -3.8 Kcal/mol. In silico docking on 3ERT and 1M17 were done to test the binding affinity of the isolated compounds to the proteins which are well known to be overexpressed in some types of cancer. Flavonoids isolated from Erythrina species have been reported to possess good antiplasmodial activity. However, due to the minute amounts isolated in the present study in-vitro assays could not be carried out. Nevertheless, in-silico assays were conducted on the most prominent protozoal parasite which causes malaria in the majority of African countries. In-silico simulations were done against Plasmodium falciparum protein (PDB ID: 7KJH), of the tested compounds Abyssinone V’ 4-methyl-ether (3) was found possess the best docking score of -4.4 Kcal/mol. The molecular docking of 7KJH was done to assess the inhibitory potential of the isolated compounds on protozoal parasites. Pharmacokinetic properties of the isolated compounds were also assessed in silico to assist in evaluating the drug likeness of these compounds. The compounds showed a percent human oral absorption of 100% except for Abyssinone V’ 4-methyl-ether (3), which showed 93.83%, this indicates a remarkable oral bioavailability. Stigamsterol (2) exhibited a Caco-2 cell permeability (QPPCaco) greater than 500 which indicates outstanding results for good intestinal absorption. The compounds also displayed a blood-brain partition co-efficient (QPlogBB) ranging from -1.433 to 0.128 suggesting they will have less potential to cross the blood-brain barrier, thus reducing any CNS related toxicity. Molecular networking of the crude extracts and the fractions was done through GNPS which allowed the identification of known compounds including one isolated in the present study, Abyssinone V’ 4-methyl-ether (3). Possible derivatives that have not been isolated from this plant before were also putatively identified. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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