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Masters Degrees (Biological Sciences)

Permanent URI for this collectionhttps://hdl.handle.net/10413/12380

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Browsing Masters Degrees (Biological Sciences) by Subject "Antibacterial."

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    Foliar secretory cavities of Vepris lanceolata (Lam.) G. Don (Rutaceae): micromorphology and chemical composition of the secretion.
    (2017) Nxumalo, Nozipho Ntombikayise.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
    Secretory structures such as ducts, trichomes and cavities consist of cells that are primary sites synthesizing essential oils and other phytochemical compounds with medicinal properties. Little is known about the micromorphology of secretory structures and the composition of the chemical constituents. There was no information documented on the micromorphology of secretory structures of Vepris lanceolata (Lam.) G. Don (Rutaceae family). The aim of this research was to investigate the micromorphological characteristics of foliar secretory cavities, the chemical composition of the secretion, and the antibacterial activity of leaf extracts of Vepris lanceolata. Scanning electron microscope (SEM) images by chemical fixation and freeze drying revealed no external secretory structures on the surfaces of leaves. SEM images by freeze-fracture showed secretory cavities present in the leaf blade. The cavities were embedded amongst palisade and spongy parenchyma cells, next to the vascular bundle. Cavities were made up of the lumen surrounded by varying layers of epithelial cells, depending on the secretory phase of the cavity. Semi-thin and ultra-thin sections showed that foliar cavities develop schizo-lysigenously, i.e. cavities develop by both separation and degradation of epithelial cells. Transmission electron microscope (TEM) sections showed that during the secretory stage, secretory cells contained oil droplets, vacuoles and vesicles indicating active secretion. Histochemical assays of fresh leaves showed the localization of phytochemical compounds. Cavities turned orange red when stained with Sudan III indicating the presence of lipids and pink with NADI reagent to show essential oils. Cavities also stained positive for polysaccharides, sugars, phenolic compounds, proteins and alkaloids. Phytochemical screening showed the presence of alkaloids, glycosides, carbohydrates, proteins, tannins, phenolic compounds, flavonoids, fixed oils and fats. Preliminary thin layer chromatography (TLC) showed separation of bands indicating groups of active compounds in leaf extracts. Crude (ethanolic and methanolic) and water extracts of leaves showed antibacterial activity against gram positive bacteria Staphylococcus aureus (ATCC 25923) and methicillin-resistant Staphylococcus aureus (ATCC BAA-1683); and five strains of gram-negative bacteria: Escherichia coli (ATCC 25922), Escherichia coli (carbapenem-resistant) (ATCC BAA 2340), Klebsiella pneumonia (ATCC 314588), Pseudomonas aeruginosa (ATCC 27853), as well as Salmonella typhimurium (ATCC14026) according to the disc diffusion method. Leaf extracts have tannins, alkaloids, flavonoids, essential oil and flavonoids responsible for the antimicrobial activity of the plant.
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    Morphology, phytochemistry, and medicinal properties of South African Mangifera indica L. leaves for summer and winter seasons.
    (2021) Maharaj, Arvish.; Naidoo, Yougasphree.; Dewir, Yaser Hassan.
    Herbal preparations of plants continue to present mankind with novel remedies as many of these plants contain important secondary metabolites. Plant species of the family Anacardiaceae are rich in bioactive phytochemicals. Mangifera indica (Anacardiaceae) is an introduced and naturalised species to South Africa. Herbal use of this plant has not been fully documented; however, it is used in traditional medicine. This study aimed at characterizing the morphology, phytochemistry, and biological activity of Mangifera indica leaves harvested in winter and summer. The foliar biology of the plant was conducted by various microscopy techniques such as stereo- and Scanning electron microscopy. The length and diameter of the different trichome types were measured using ImageJ. The non-glandular trichome lengths range between 70 - 200 μm. The peltate gland trichomes consist of 2 rows of 8 oblong cells each with a size ranging from 32- 48 μm. Morphological observations using stereo- and SEM revealed the presence of non-glandular trichomes with cuticular warts and glandular peltate trichomes on the leaves of Mangifera indica. Transmission electron micrographs showed the presence of numerous mitochondria, starch grains, plastoglobuli, and plastids. The results for summer and winter leaves resembled somewhat similar-to-identical morphological characteristics on all fronts. For the phytochemical and biological assays, this study aimed to investigate some of the phytochemical and biological properties using different solvents (hexane, chloroform, and methanol) for extraction of the leaves of Mangifera indica for the summer and winter seasons. Preliminary phytochemical screening for the hexane, chloroform and methanolic extracts was done using a reflux extraction apparatus to uncover the presence of different metabolites and the anti-oxidant screening was done by the radical scavenging activity, which was established using the 2,2-diphenyl-1-picrylhydrazyl assay. Potent radical scavenging activity was exhibited for both summer and winter seasons with hexane and methanolic extracts for summer (IC50 of 19.53 μg/mL and 12.71 μg/mL respectively) and winter (22.32 μg/mL and 14.35 μg/mL respectively) in comparison to the control ascorbic acid which produced an IC50 of 3.20 μg/mL. The summer extracts had better radical scavenging IC50 capacity than winter extracts. The antibacterial activity of the methanolic leaf extracts for summer and winter of Mangifera indica were evaluated against the bacterial species: Gram-negative Escherichia coli (ATCC 25922) and Gram-positive: Staphylococcus aureus (ATCC ATCC 43300). For S. aureus (ATTC 43300), the summer crude extract displayed lower antibacterial activity than the control streptomycin, the summer extracts had a zone of inhibition of 14.17 mm while streptomycin had a 16.67 mm zone of inhibition. winter extracts had a zone of inhibition of 12 mm while streptomycin had a 13.67 mm zone of inhibition. For E. coli (ATCC 25922), the summer crude extract displayed higher antibacterial activity than the control gentamycin; the summer extract had a zone of inhibition of 18.05 mm while gentamycin had a 17.5 mm zone of inhibition. The winter extracts had a zone of inhibition of 8.5 mm. while gentamycin had a 14.5 mm zone of inhibition. Between seasons, summer had better antibacterial activity compared to winter for both Gram-positive and Gram-negative bacteria. Phytochemical screening showed the presence of phenols, flavonoids, tannins, and terpenoids, alkaloids, phytosterols, saponins, steroids, and carbohydrates. Potent radical scavenging activity was exhibited for the hexane and methanolic extracts for summer and winter, indicating that Mangifera indica is a potential source of medicinally important compounds. Antibacterial screening showed positive results with antibacterial properties for both summer and winter samples revealing its valuable biological activities. Summer overall performed better than the winter season. Future studies on this plant species are recommended to advance the use of indigenous herbal medicine or produce novel drug leads. To our knowledge, this study represents the first recent investigation in South Africa describing key foliar micromorphological features, phytochemicals, and biological activities of Mangifera indica L.