Theses and dissertations (Applied Sciences)

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The accumulation of heavy metals by aquatic plants
(2003) Maharaj, Saroja; Moodley, Kandasamy Govindsamy; Southway-Ajulu, F. A.; Baijnath, Himansu
The pollution of water bodies by heavy metals is a serious threat to humanity. The technique known as phytoremediation is used to clean up these polluted water bodies. The accumulation of heavy metals by aquatic plants is a safer, . cheaper and friendlier manner of cleaning the environment. The aquatic plants -studied in this project are A.sessilis, P.stratiotes, R.steudelii and T.capensis. The accumulation of heavy metals in aquatic plants growing in waste water treatment ponds was investigated. The water, sludge and plants were collected from five maturation ponds at the Northern Waste Water Treatment Works, Sea Cow Lake, Durban. The samples were analysed for Zn, Mn, Cr, Ni, Pb and Cu using ICP-MS. In general it was found that the concentrations of the targeted metals were much lower in the water (0.002 to 0.109 mg/I) compared to sediment/sludge (44 to 1543mg/kg dry wt) and plants (0.4 to 2246 mg/kg dry wt). These results show that water released into the river from the final maturation pond has metal concentrations well below the maximum limits set by international environmental control bodies. It also shows that sediments act as good sinks for metals and that plants do uptake metals to a significant extent. Of the four plants investigated it was found that }t.sessi[ir (leaves, roots and stems) and }A.sessilis (roots and stems) are relatively good collectors of Mn and Cu respectively. These findings are described in the thesis. The concentration of heavy metals in the stems, leaves and roots of the three plants were compared to ascertain if there were differences in the ability of the plant at different parts of the plant to bioaccumulate the six heavy metals studied.
Effects of processing on the characteristics of flour and protein isolates produced from Lablab purpureus
(2020) Naiker, Tremayne Sheldon; Mellem, John Jason; Amonsou, Eric Oscar; Baijnath, Himansu
The utilization of legumes by food industries has grown considerably in intermediate forms other than whole grains. Thus, continuous work is focused on modifying legume-based raw materials for improving its techno-functional properties whilst preserving its nutritive value. The study conducted was aimed at analyzing the effects of processing treatments on the characteristics of flour and protein isolates produced from Lablab purpureus (L.) Sweet (hyacinth bean). Flour was produced from legume grains subjected to steaming (S+A) and dehydration (S+A+D) treatments, following soaking (S). Protein isolates were produced from respective flour fractions using isoelectric precipitation. Samples produced from steaming and dehydration was found useful for potential application as functional food ingredients for nutritional intervention. The respective flour samples contained improved resistant starch (23.44 g/100 g dry starch) content. Swelling and solubility indices were found to be greater at lower temperatures mainly attributed to the pre-gelatinization of starch granules. Thus, they may be potentially suitable for ingredient application in texture modified foods. Protein isolates produced displayed traits typical of high-quality proteins and demonstrated exceptional functionality. The rapid increase in predicted biological values observed suggested improved protein digestibility potential. Samples contained significant concentrations of branched chain and aromatic amino acids highlighting potential health benefits. Protein nanoparticles were produced using Ca2+-induced aggregation (0.00-6.50 mM) from hyacinth bean protein isolate (2% m/v, pH 7). This was to examine its potential for development as food- grade Pickering emulsion stabilizers. Protein solutions containing high Ca2+ concentrations resulted in higher dynamic viscosities (mPa.s). Protein nanoparticles (~172.38 nm) were formed at 3.50 mM Ca2+. The z-average diameter of aggregates was dependent on Ca2+ concentration. Results satisfied certain criteria for nanoparticles to potentially function as Pickering stabilizers. However, nanoparticles were susceptible to 4 M Urea and emulsion creaming became more apparent as storage progressed. The study conducted provides valuable information on how processing could be useful for obtaining value-added legume grain ingredients for potential food applications. Such approach could diversify the use of hyacinth bean and help improve the competitiveness of the legume grain sector.
The essential oil from Cymbopogon validus
(2007) Naidoo, Nelisha; Odhav, Bharti; Baijnath, Himansu
The chemical and biological properties of the essential oil from Cymbopogon validus were investigated. Hydro-distillation was used to extract the oil from C. validus, the flower-heads, leaves, culms and rhizomes. The percentage oil yields obtained from the plant organs varied from 0.05 to 1.23%, with the greatest concentration found in the flower-heads and rhizomes, 1.23 and 1.12% respectively. A sensory evaluation of the oil revealed that the essential oil was slightly murky, pale yellow in colour, had a strong turpentine-like smell and remained liquid at room temperature. The oxidative stability of C. validus oil was evaluated by determining its Rancimat induction period (negative), peroxide value (60.56 meq/kg), iodine value (84.55), percentage free fatty acids (0.19%) and percentage cholesterol (3.03%). These results indicated that the oil was highly susceptible to oxidation. Chromatographic profiles of the oils from C. validus, as well as the plant organs were generated using gas chromatography-mass spectroscopy (GC-MS). Predominant compounds present in the oil included alpha-Cubebene, Camphene, Geraniol, Limonene, Myrcene, Palmitic acid and Sabinene. C. validus essential oil was also investigated for its antimicrobial (disk diffusion), antioxidant (1, 1-Diphenyl-1-Picrylhydrazyl (DPPH) assay), anti-inflammatory (5-lipoxygenase assay), anti-mosquito properties (insecticidal, larvicidal and repellency assays) and toxicity profile (Brine shrimp and Ames assays). The oil showed poor antimicrobial activity and inhibited the growth of only Gram positive bacteria with a minimum inhibitory concentration (MIC) of 0.0625 (vol/vol) for Bacillus, Micrococcus and Staphylococcus species. The oil also exhibited excellent antioxidant activity, scavenging more than 80% of DPPH free radicals and possesses anti-inflammatory activity (IC50=190 ppm). C. validus oil showed good adulticidal activity (53.7% mortality) and excellent larvicidal (100% mortality) and repellent activity (100% repellency) against Anopheles arabiensis mosquitoes. At high concentrations, the oil was toxic to brine shrimp larvae. However, when diluted it was safe and the minimum inhibitory concentration was 0.0001(vol/vol). The absence of revertant colonies at all essential oil concentrations in the Ames test suggest that the oil is not mutagenic. These results lead the way for exploiting C. validus oil as a multi-functional agent that has antibacterial, anti-oxidant, anti-inflammatory, and anti-mosquito properties.
Hypoxis colchicifolia as a potential nutraceutical to address non-communicable diseases
(2020) Moodley, Suggessan; Mellem, John Jason; Baijnath, Himansu
Cancer, hypertension and hyperglycaemia affect millions of individuals worldwide, with many succumbing to these diseases. Conventional medicine and treatments currently used to manage these diseases, although highly effective, have major side effects. Hypoxis colchicifolia is a traditional medicinal plant used in Southern African against an array of ailments. Providing a rationale and assessing the toxicity of the plant is essential for future use as a natural alternative to allopathic medicine. In this study H. colchicifolia corm and leaf extracts were qualitatively assessed for their phytochemical constituents. The total phenolic content was determined using the Folin Ciocalteu method, and toxicity screened using the brine shrimp lethality assay. The antioxidant potential was evaluated using the DPPH (1,1-diphenyl-2-picryl-hydrazyl), ABTS (2,2′-azinobis(3- ethylbenzothiazolline)-6-sulfonic acid), PM (Phosphomolybdenum), CUPRAC (Cupric ion reducing antioxidant capacity) and FRAP (Ferric Reducing Antioxidant Power) radical scavenging methods. This study also evaluated the in vitro anti-diabetic (α-amyalse and α-glucosidase), antihypertensive [ACE (angiotensin-converting enzyme)] and anticancer potential of H. colchicifolia corm as well as leaf solvent extracts (acetone, methanol and aqueous). All extracts showed the presence of key phytochemical constituents and produced no toxicity. There was a clear difference in the total phenolic content of the leaves compared to the corms. Extracts showed good antioxidant potential with different extracts inhibiting different free radicals, indicating selective antioxidant scavenging capacity. The extracts of leaves and corms cannot be used interchangeably as there are differences in the phytochemical composition. Results showed that H. colchicifolia extracts have a moderate anti-diabetic and anti-hypertensive potential. The acetone extract of fresh corms had the best α-amylase potential with an IC50 of 337 µg/mL and acetone extract of fresh corms leading the α-glucosidase inhibition with an IC50 of 22.06 µg/mL. The methanol extract of dried corms exhibited the greatest ACE inhibition with an IC50 of 368.20 µg/mL. Methanol extract of dried leaves showed the least cytotoxicity against non-cancerous cell line HEK-293. Methanol extract of dried leaves inhibited MCF-7 cell line with an IC50 of 3.24 µg/mL, which was lower than that of the positive control, camptothecin (IC50, 8.44 µg/mL). All extracts exhibited a greater inhibitory potential in A549 cells than camptothecin (IC50, 304.20 µg/mL), with aqueous extract of dried corms having the greatest potential of IC50 32.22 µg/mL. This study reveals that H. colchicifolia has potential to act as a therapeutic.
Immune modulatory effect of Dichrostachys cinerea, Carpobrotus dimidiatus, Capparis tomentosa and Leonotis leonurus
(2009) Hurinanthan, Vashka; Odhav, Bharti; Baijnath, Himansu
Dichrostachys cinerea, Carpobrotus dimidiatus, Capparis tomentosa and Leonotis leonurus are all plants that are indigenous to South Africa. These plants are used in traditional medicine to treat various ailments. However, there is little or no scientific data to justify these traditional uses. Furthermore, it is difficult to reconcile traditional knowledge with scientific evidence because of the overwhelming targeting of signal-responsive systems by plant defensive compounds, multiple sites of action and the connectedness of the signaling pathways, which provide many cures and have pleiotropic effects. In order to evaluate the action spectrum of these plants, and validate its widespread use, this research evaluated the antibacterial, antioxidant, anti-inflammatory, anti-mosquito and immunomodulatory properties of these plants. Antimicrobial activity of the extract was determined by evaluating the bactericidal and fungicidal action using the agar disc diffusion assay. Anti-oxidative properties of the extracts were tested using the DPPH photometric assay. Anti-inflammatory properties were carried out using the 5-lipoxygenase assay. The larvicidal, repellency and insecticidal assay was determined against A.arabiensis. The safe use of these plant extracts was determined by evaluating toxicity, a brine shrimp lethality assay and an in vitro cell culture system using human myelogenous leukemia cell line. Potential carcinogenic activity was evaluated using the Ames Salmonella Mutagenecity assay. The immunomodulatory activity of the extracts on human peripheral blood mononuclear cells 6 was evaluated on freshly harvested lymphocytes using the MTT assay. Cytokine response was evaluated by measuring the secretion of interferon-gamma and interleukin-10. Elucidation of the B cells, T cells, activated T cells, CD 4+, CD 8+ and NK cells was performed by flow cytometry. The extracts showed anti-microbial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella oxytoca, Salmonella typhimurium, Serratia marcescens, Bacillus cereus and Tricoderm sp. The highest activity was shown by methanolic and aqueous extracts of L. leonurus leaves followed by methanolic and aqueous extracts of D. cinerea. Extracts of C. tomentosa and D.cinerea demonstrated a higher degree of free radical scavenging than rutin, which was used as a standard indicating that these plants have strong antioxidant properties. None of the plants showed significant anti-inflammatory activity when compared to NDGA. In the anti-mosquito assays, the extracts showed strong repellency and insecticidal activity. L. leonurus extracts demonstrated the highest insecticidal and repellency activity against the mosquito, and was also found to cause ‗knockdown‘ and mortality. The extracts display no toxicity, cytotoxicity and mutagenicity. The immunological studies for immune modulation showed that the methanol extracts of these plants induce a Th1- predominant immune response because they significantly suppressed the secretion of IL-10 and augment IFN-γ production, which are hallmarks used to indicate a stimulation of the innate immune response. This study also provides new information, with respect to the potential use of these plants in producing a mosquito repellent and an immunostimulant.