A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2014. / Heavy 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/16828 |
| Date | 30 January 2015 |
| Creators | Makita, Charlene |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
Page generated in 0.0017 seconds