3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Assessing the effect of extreme temperature conditions on the morphology, anatomy and phytochemistry of Moringa Oleifera leaves(2018) Ntsangani, LuvoSince its discovery in India many centuries ago, Moringa oleifera has been used largely in the tropics and subtropics where it is native for nutritional, medicinal and industrial benefits. These benefits are attributed to the antioxidant, antifungal and anti-inflammatory properties in the phytochemical compounds of M. oleifera. Agriculture of M. oleifera in South Africa is currently minimal despite its multiple benefits. Naturalisation of M. oleifera in the country is important in the aid to eliminate the shortage of nutritional food reserves, and utilise the plant as a source for realising and developing new medicinal compounds. Global warming and consequent climate change have caused extreme high and low temperature seasons in the past in South Africa. Studying the effects of extreme high and low temperatures on the growth, performance and phytochemistry of M. oleifera at controlled conditions is vital in understanding its responses and adaptability. M. oleifera grown for three months in a greenhouse of the University of the Witwatersrand was subjected to two extreme temperature conditions of 15/10°C and 47/29°C for seven days (144 hours). The control was kept at ambient temperature (25/22°C). The morphology, histology, total phenolic contents, total flavonoid contents, quercetin and kaempferol concentrations were assessed using dissecting microscope, light electron microscope, UV-Vis spectroscopy and HPLC-UV respectively. The effect of high temperatures showed increased senescence. However, plants that were treated with low temperature appeared to be more tolerant by indicating a delay in leaf senescence. Yellowing, browning, curling and drying of the leaves worsened after 144 hours at high temperature treatment. The histological examination at high temperatures showed intact cellular structures such as upper epidermis, lower epidermis, spongy mesophyll, palisade mesophyll and intercellular spaces in green leaves after 24 hours. However, leaf size decreased over the seven days treatment. The cellular structures in leaves that became yellow had collapsed and showed evidence of necrosis. In the low temperature treatment, 1% of leaves showed signs of leaf curling after VII 48 hours while others remained green and intact. After 144 hours, 5% of leaves showed signs of senescence while others turned dark green and remained intact. Leaves cells such as palisade mesophyll had elongated and thus increased the thickness of the leaves. This was evidence of acclimation to cold temperatures. The total phenolic content increased by 10.1% after 48 hours under high temperatures. However, a decrease of 3.5% and 3.1% was observed after 96 and 144 hours respectively. Quercetin increased by 8.5% after 48 hours then after 96 and 144 hours a decrease of 41.7% and 61.6% was observed respectively. A significant increase in kaempferol concentration of 203.5% after 48 hours was noted. This was followed by a decline after 96 and 144 hours of 43.0% and 24.8% respectively. Concentration of total flavonoid content increased by 11.6% and 33.8% after 48 and 96 hours, and after 144 hours, a decline of 0.4% was observed. The combined evidence from the present study showed that the three months old M. oleifera plants are sensitive and cannot withstand temperatures as high as 47/29°C. However, the species has showed to be positively more tolerant to cold temperatures (15/10°C). This evidence may have meaningful contribution towards the industry, Moringa oleifera farming practices as well as advance the understanding of the effects of extreme temperatures on the species.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.