3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Metabolomic exploration of pharmacologically relevant metabolites in Moringa oleifera and Moringa ovalifolia through the use of UPLC-qTOF-MS and multivariate models(2017) Makita, Charlene SampuPlant metabolomics is considered a holistic qualitative and quantitative analysis of primary and secondary metabolites under specific conditions. Metabolomics provides functional information that is important in the biological studies of plants. Moreover, chromatographic techniques in combination with mass spectrometry are presently commonly utilized analytical technologies that are used in metabolomics studies. Moringa oleifera (M. oleifera) is an acclaimed medicinal herb and is considered one of the most superior plants based on its nutritional and medicinal attributes. Signature compounds such as chlorogenic acids and flavonoids found in Moringa plants are considered beneficial as they are responsible for the health properties found in these plants. Out of the 13 species belonging to the Moringaceae family, M. oleifera is the most widely studied. Furthermore, plants are known to produce compounds, such as flavonoids, as a response to biotic stresses (pest resistance) and abiotic stresses (harsh environmental conditions such as drought or cold). Other species belonging to the Moringaceae family such as Moringa ovalifolia (M. ovalifolia), located in the dry desert and semi-desert areas of Namibia, has not been reported much in literature. Moreover, there is very little work done on other classes of compounds that are possibly present in M. ovalifolia. Therefore, the significant correlation between desert plants and their possible increased flavonoid content is of interest in this study and is worth investigating. Moreover, in an effort to compare Moringa species in that regard, a holistic approach to metabolite fingerprinting using UPLC-qTOF-MS was thus employed for the characterization of possible metabolite markers and taxonomical differences in M. ovalifolia and M. oleifera plant species (Paper I). From the results, 17 flavonoid compounds were identified. Interestingly, M. oleifera and M. ovalifolia had a similar aglycone profile, however, they had a different sugar moiety. Rutinoside sugar moieties were only found to be present in M. ovalifolia indicating that it is only capable of attaching the rutinoside sugar moiety to its flavonoid skeleton. M. oleifera, however, is capable of attaching many sugar moieties to its flavonoid skeleton. The outcomes of this research additionally demonstrated for the first time the significance of sugar attachment for taxonomical classification of related species and that the contrasts between the grouped species are likely because of genetic variations as opposed to environmental influences. This study further provided potential chemotaxonomic biomarkers and a classification model was generated to classify and differentiate between closely related Moringa species utilizing multivariate analysis (Paper III). Moreover, chlorogenic acids which are esters formed between derivatives such as cinnamic acid and quinic acid molecules, were identified in M. ovalifolia plants species for the first time (Paper II ). Chlorogenic acids are difficult to identify and differentiate since they are structurally complex. This study demonstrated the effectiveness of an UPLC-ISCID-MS/MS based platform to aid in the profiling of isomers and derivatives of chlorogenic acids present in M. ovalifolia. This approach further showed M. ovalifolia as a valuable source of molecules with therapeutic potential. Based on the classification model generated in Paper II, the biomarkers identified were utilized in order to differentiate between 12 M. oleifera cultivars (Paper III). Three sought after flavonoid compounds, namely, quercetin rutinoside (rutin), kaempferol rutinoside and isorhamnetin rutinoside were identified as potential chemotaxonomic markers amongst the 12 Moringa cultivars. Metabolite distribution patterns of the 12 cultivars were analyzed using a metabolomics approach with the aid of UHPLC-qTOF-MS in combination with multivariate data models such as principal component analysis (PCA), hierarchical clustering analysis (HCA) and box-whiskers plot. According to the results, three main cultivars, namely: TOT4977, CHM and TOT5330 were identified as potential cultivars for pharmacological and nutritional purposes according to the presence and abundance of the three studied rutinoside bearing flavonoid molecules.Item A study of the elemental analysis and the effect of the pressurised hot water extraction method (PHWE) on the antibacterial activity of Moringa oleifera and Moringa ovalifolia plant parts(2015-01-30) Makita, Charlene SampuHeavy metal pollution is an increasing phenomenon and contamination of these heavy metals has detrimental effects on the environment and humans. The concentrations of metals in the soil, leaves, stem bark and flowers of Moringa ovalifolia sampled from Okahandja, Okaukuejo, Halali and Tsumeb in Namibia were investigated. Acid digestion of all samples was performed utilising the microwave technique. Determination of elements from the extracts were analysed by inductively coupled plasma - optical emission spectroscopy (ICP-OES). No lethal amounts of heavy metals were found in the soil, leaves, stem bark and flowers of Moringa ovalifolia. The results from Moringa ovalifolia was compared to spinach from another similar study. On average, Moringa leaves contained more or less similar amounts of Zn (29.4 mg kg-1) and Cr (13.2 mg kg-1) but higher higher amounts of Fe (263.8 mg kg-1) concentrations than spinach, with values of Zn (30.0 mg kg-1), Cr (20.0 mg kg-1) and Fe (190 mg kg-1) from a previous study. In this study, selected statistical methods such as correlation analysis and principal component analysis were used to identify the origin of these metals in the soil, leaves and stem bark collected from the Moringa farm, national parks and the road side in Namibia. From the correlation analysis, it was found that Co, Mg, Cr and Mg pairs were highly significant to each other. The principal component analysis revealed that heavy metals gave 53.41% of the total variance in factor 1. Sources of Mg and Ni could be from vehicle emissions. Factor 2 revealed As, Co, Al, and Si contributing to a total variance of 25.15% Co suggesting that the metals present could be as a result of geologic sources. This iii study proves that statistical analysis may provide a scientific foundation for the observation of heavy metal accumulation in samples. Pressurised hot water extraction (PHWE) was used for the extraction of bioactive compounds from the leaves and stem bark of Moringa ovalifolia and Moringa oleifera samples. The aim of the study was to assess the effect of temperature and extraction process of the Moringa extracts on Staphylococcus aureus (S. areus), Enterococcus faecalis (E. faecelis) and Pseudomonas aeruginosa (P. aeruginosa). The antibacterial activities of the extracts at varying temperatures were evaluated using the disk diffusion method where the zones of inhibition were recorded. ANOVA, which was calculated at a significance level of 0.05, was used to analyse the data. Antimicrobial activity of the stem bark extracts and leaf extracts from different sites extracted at 25˚C and 80˚C showed significant difference. As temperature increased, a decrease in inhibition was observed for stem bark extracts from different sites tested again S. areus, E. faecelis and P. aeruginosa. When the PHWE stem bark extracts collected in Tsumeb, were compared with ethanol and cold water extractions, the PHWE had more activity than other two methods. This proves that PHWE may be used as a novel extraction to get essential compounds from indigenous plant materials.