Thesis ( (M.Sc.)(Wildlife Management)--University of Pretoria, 2001. / Summary in English. Includes bibliographical references.

Thesis (M. Inst. Agrar.(Horticulture)) -- University of Pretoria, 2008. / Includes summary. Includes bibliographical references.

The genus Evides Dejean, 1833 (Coleoptera: Buprestidae) belongs to the family of woodboring beetles commonly known as jewel beetles. This comparative study was undertaken on the morphological characteristics of three species from field specimens, private collections and collections at the Transvaal Museum of Natural History. The genus Evides consists of eleven species and one subspecies in total worldwide. Nine species and one subspecies are endemic to Sub-Saharan Africa. One species is recorded from India and further species from Laos and Vietnam: Bellamy (World Catalogue, in prep.) The objective of the study was to quantify morphological differences between species representing the genus in South Africa. Specimens of E. gambiensis (Laporte & Gory, 1835), E. interstitialis (Obenberger, 1924) and E. pubiventris (Laporte & Gory, 1835) were collected in the Waterberg (Limpopo Province) and additional specimens of E. pubiventris were collected at Ezemvelo Nature Reserve (Gauteng Province). All three species are related, difficult to differentiate in the field and occur on the same host plants, marula (Sclerocarya birrea (A. Rich.) Hochst.) and false marula (Lannea discolor (Sonder) Engl.). Results indicate that there are morphological differences and species can be differentiated according to elytra length, total elytron width, eye size, frons length, frons width and abdomen length.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Wildlife Management))--University of Pretoria, 2007. / Animal and Wildlife Sciences / unrestricted

Metabolomics is a discipline where metabolites are assessed, identified and quantified in different samples. Metabolites are crucial components of the biological system and highly informative about its functional state due to the closeness to functional endpoints and to the organism’s phenotypes. 1H NMR and LC-MS, the commonly used metabolomics analytical platforms were used to annotate the metabolites found in Sclerocarya birrea (S. birrea) leaves from five South African provinces, Limpopo (L), Gauteng (G), North West (NW), Mpumalanga (M) and KwaZulu-Natal (KZN). Supervised Orthogonal Partial Least Square – Discriminant Analysis (OPLS-DA) of the full spectra revealed a clear differentiation of S. birrea leaves from five provinces. In addition, the level of common metabolites were measured and compounds previously found to have anti-diabetes potential ((-)-epicatechin 3-0-galloyl ester, myricetin-3-0-α-L-rhamnopyranoside, gallic acid and Kaempferol-3-0-α-L-rhamnopyranoside) were annotated in the samples. The samples from the five provinces showed anti- diabetic activity when exposed to an in-vitro glucose uptake assay, with the highest activity observed in male samples from M. The sample presented high concentrations of (-)-epicathechin 3-0-galloyl ester, one of the metabolites with anti-diabetes activity. Overall 1H NMR and LC-MS metabolic profiling were successfully applied to discriminate all five sources of S. birrea leaves, and obtained qualitative information of many common metabolites / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Thesis (MSc (Biochemistry))--University of Limpopo (Medunsa Campus), 2009. / Background and Purpose The stem bark, roots and leaves of Sclerocarya birrea (S. birrea), {(A. Rich) Hochst}, subspecies caffra (Sond) Kokwaro are widely used in South Africa and some African countries as folk medicine in the treatment and management of a variety of human ailments, including diabetes mellitus. Although the blood glucose lowering effect of the stem bark extract of S. birrea have been confirmed using experimental animal models of diabetes, there is no clear understanding of the mechanism(s) whereby S. birrea stem bark extracts and/or their components exert their blood glucose lowering effects. The primary aim of the current study was to study the in vitro inhibitory effects of S. birrea stem bark extracts on the activities of selected diabetic related carbohydrate metabolizing enzymes (α-amylase, α-glucosidase and glucose 6-phosphatase). The current study also investigated the acute in vivo effect of S. birrea stem bark acetone extract on postprandial blood glucose levels after oral sucrose loading as well as the effect of S. birrea stem bark aqueous extract on hepatic glucose 6-phosphatase activity. In addition, the long term (21 days) effects of S. birrea stem bark acetone extract on fasting blood glucose levels, plasma insulin levels, plasma triglyceride and body weight in normal and alloxan induced diabetic rats were also investigated. Methods For in vitro studies: Crude hexane, acetone, methanolic and aqueous extracts of the stem bark extract of S. birrea were prepared by means of a sequential solvent extraction procedure and screened for inhibitory activities against human urinary α-amylase, rat pancreatic α-amylase, Bacillus stearothermophilus α-glucosidase and rabbit liver glucose 6-phosphatase using standard procedures for assaying the activities of these enzymes. IC50 values and mode of inhibition of extracts demonstrating appreciable inhibitory activity against α-amylase and α-glucosidase were determined and compared with those of acarbose, a known inhibitor of these two enzymes. The IC50 value and mode of inhibition of extracts demonstrating appreciable inhibitory activity against glucose 6-phosphatase were determined and compared with those of sodium orthovavadate and sodium tungstate, known inhibitors of glucose 6-phosphatase. In vivo studies: In vivo studies were conducted in normal and alloxan induced diabetic male WKY rats. Diabetes was induced in rats that had been fasted for 12 h by a single intraperitoneal injection of 140 mg/kg body weight of alloxan monohydrate freshly dissolved in sterile normal saline. The effect of S. birrea stem bark acetone extract on postprandial blood glucose level was determined in 18 h fasted diabetic and normal rats by administering orally, the plant extract (300 mg/kg) 30 minutes before an oral sucrose loading and measuring postprandial blood glucose levels after sucrose loading by means of a MediSense’s Optimum Xceed Glucometer (MOXG). In addition, rat intestinal dissacharidase (α-glucosidase/sucrase) activity was determined in homogenate of small intestine of rats sacrificed one hour after given orally either plant extract or acarbose. The in vivo effect of S. birrea stem bark extract on glucose 6-phosphatase was determined by measuring the activity of hepatic glucose 6-phosphatase at the end of the study. For the determination of the long term (chronic) effect of S. birrea stem bark crude acetone extract on blood glucose levels, body weight and water intake, alloxan induced diabetic and normal WKY rats were treated daily with S. birrea stem bark crude acetone extract (300 mg/kg) for 21 days. Fasting blood glucose levels and changes in body weight were determined on day 0, 7, 14 and 21 after initiation of treatment by means of a MOXG and gravimetrically respectively. Water intake was determined on the same days that blood glucose levels were determined by measuring the amount of water left overnight by each rat and subtracting this amount from the initial amount water given to each rat. Blood was also collected at the end of the study for the measurement of plasma glucose, triglyceride and insulin levels. Plasma glucose and plasma triglyceride levels were measured using commercially available kits based respectively on the glucose oxidase and the glycerol blanked methods (Beckman Coulter®’s UniCell DXC 800 Synchron® Clinical System). Plasma insulin levels were determined by means of an enzyme linked immunosorbant assay (ELISA) adapted to the Beckman Coulter® Ireland Inc’s UniCell DXI 800 Access® Immunoassay System. Results In vitro studies: The crude methanolic and acetone S. birrea stem bark extracts strongly inhibited both human urinary α-amylase and rat pancreatic α-amylase in a competitive manner. The inhibitory effect of the crude methanolic extract on both enzymes was significantly stronger than acarbose. Hexane and acetone crude extracts of the stem-bark of S. birrea demonstrated the highest percentage inhibition against B. stearothermophilus α-glucosidase. The mode of inhibition of the crude hexane extract on B. stearothermophilus α-glucosidase appeared to be a noncompetitive one. However, the this plant extract appeared to be a less potent inhibitor of α-glucosidase enzyme than acarbose. Rabbit liver glucose 6-phophatase was strongly inhibited by the crude aqueous S, birrea stem bark extract in a competitive manner. In vivo studies: Administration of S birrea stem bark acetone extract 30 min before oral sucrose loading significantly suppressed (P < 0.01) the rise in postprandial blood glucose levels in treated rats compared to control rats. The crude extract also decreased significantly the intestinal disaccharidase activity of experimental rats compared to control rats. These observations suggest that the in vitro inhibitory effects of the crude hexane extract on α-glucosidase enzymes are applicable in vivo Daily, continuous oral treatment of alloxan–induced diabetic and normal WKY rats with S. birrea stem bark extract for 3 weeks resulted in significant reductions in fasting blood glucose levels and water intake of treated diabetic rats compared with diabetic controls. The extract, however, failed to bring about any significant change in the body weight, plasma insulin levels, plasma triglyceride levels and hepatic glucose 6-phosphatase of treated diabetic rats compared to diabetic control rats Conclusions The results of the current study suggest that the observed in vitro inhibitory effect of S. birrea stem bark acetone extract on alpha glucosidase enzymes are applicable in vivo whereas the observed in vitro inhibitory effect of S. birrea stem bark aqueous extract on glucose 6-phosphatase are not applicable in vivo. Furthermore, in the current study S. birrea stem bark acetone extract appears to lower blood glucose levels of alloxan induced diabetic rats without increasing their plasma insulin levels. Thus, it can be concluded on the basis of the current study that S. birrea stem bark acetone and hexane extracts exert their blood glucose lowering effect in alloxan induced diabetic rats in part, through inhibition of intestinal brush border α-glucosidase enzymes.

MSc (Botany) / Department of Botany / The overall aim of this study was to determine the population biology of Sclerocarya birrea (A Rich) Hochst., subspecies caffra (Sond) at Nylsvley Nature Reserve, Limpopo, South Africa. Sclerocarya birrea is a keystone plant species which is rated as one of the most highly valued indigenous trees because of its multiple uses. It is identified as a key species to support the livelihood of rural communities and it is central to various commercial activities. Sclerocarya birrea is also widely used by game in protected areas and by humans in communal areas for its fruit, wood and medicinal properties. Understanding the population biology for this key stone species is important as there are many environmental factors that are affecting its population structure. The study found that the population of S. birrea at Nylsvley Nature Reserve is fairly healthy and is mainly comprised of seedling and adult trees. Evidence of predators feeding on the seeds of Sclerocarya birrea was also recorded in this study. Additionally, disturbance, such as fire and cutting do not have negative impact on S.barrea

Thesis (MSc. (Microbiology)) --University of Limpopo, 2018 / Refer to the document / National Research Foundation (NRF)

Sub-Saharan Africa is a treasure chest of natural materials remaining to be explored for commercial applications and as alternative foods to diversify and improve food sustainability. The Marula tree is available in abundance in South Africa and bears a fruit with a highly nutritious kernel containing high oil and protein content. The oil from the kernels has various applications from food to cosmetics. The accepted oil processing practice is required to be a green technology, producing no effluent or using toxic solvents. Therefore, the oil is extracted using an expeller. However, with average 55 wt. % oil in the kernel the extracted oil yield is far from optimal, typically ranging from as low as 7 wt. % to 47 wt. %. The latter is obtained only with proprietary modified expellers. Therefore, an alternative green technology which retains the native characteristics of the Marula oil is needed. Communication with local producers, South African and Namibian, confirmed the need for investigation of an alternative means of extraction of Marula oil from the seed kernels which can improve the yield and potentially the quality of the oilcake. The latter of which is typically adversely affected by the expelling process. A review of various processing technologies available for oil extraction was completed and supercritical fluid extraction utilizing carbon dioxide as the extraction solvent was identified as a potential solution. An overview on supercritical fluid extraction using carbon dioxide (SFE-CO2) of similar materials to the Marula kernels, such as hazelnuts, walnuts and pine kernels indicates that yields similar to that of solvent extraction and of the quality of the oils obtained by cold pressing can be obtained with the technique. The theory, practical applications, and how one can use the system to improve yield from various natural materials were reviewed. It was determined that the two main parameters one can manipulate on supercritical extraction systems to optimize the yield, were pressure and temperature. Subsequently kernels of the Sclerocarya birrea tree, common name Marula, cultivated in South Africa, were obtained for extraction with supercritical carbon dioxide. The effects of pressure and temperature on extraction yield were investigated. The total maximum yield of Marula kernel oil obtained was found to be 54 wt. %, compared to a solvent extracted yield of 52 wt. %, such that a 100 % oil recovery was obtained with SFE-CO2. The optimal conditions were found to be 450 bar and 60 °C as the yield per kg solvent initially was 41 g kg-1 CO2. Following the extractions, the oils were characterized for fatty acid composition using gas chromatography. Quality parameters of a cold pressed sample and a sample obtained at the optimal extraction conditions were determined and compared; and the results indicate that the two oils are of similar composition and quality. Supercritical fluid extraction using carbon dioxide was successfully verified as a potential processing method for the extraction of Marula oil from the kernels. The SFE-CO2 provided an improved yield compared to cold pressing and a quality of oil similar to cold pressed Marula oil. Additionally, after SFE-CO2 processing, the defatted Marula kernels contain high protein content, 69 wt. %, in the form of a pure white powder. Due to the favourable nutritional content the residue may be used for human consumption to create new products such as meat analogues, porridges, and shakes, or can be sold as a high protein powder. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Sub-Saharan Africa is a treasure chest of natural materials remaining to be explored for commercial applications and as alternative foods to diversify and improve food sustainability. The Marula tree is available in abundance in South Africa and bears a fruit with a highly nutritious kernel containing high oil and protein content. The oil from the kernels has various applications from food to cosmetics. The accepted oil processing practice is required to be a green technology, producing no effluent or using toxic solvents. Therefore, the oil is extracted using an expeller. However, with average 55 wt. % oil in the kernel the extracted oil yield is far from optimal, typically ranging from as low as 7 wt. % to 47 wt. %. The latter is obtained only with proprietary modified expellers. Therefore, an alternative green technology which retains the native characteristics of the Marula oil is needed. Communication with local producers, South African and Namibian, confirmed the need for investigation of an alternative means of extraction of Marula oil from the seed kernels which can improve the yield and potentially the quality of the oilcake. The latter of which is typically adversely affected by the expelling process. A review of various processing technologies available for oil extraction was completed and supercritical fluid extraction utilizing carbon dioxide as the extraction solvent was identified as a potential solution. An overview on supercritical fluid extraction using carbon dioxide (SFE-CO2) of similar materials to the Marula kernels, such as hazelnuts, walnuts and pine kernels indicates that yields similar to that of solvent extraction and of the quality of the oils obtained by cold pressing can be obtained with the technique. The theory, practical applications, and how one can use the system to improve yield from various natural materials were reviewed. It was determined that the two main parameters one can manipulate on supercritical extraction systems to optimize the yield, were pressure and temperature. Subsequently kernels of the Sclerocarya birrea tree, common name Marula, cultivated in South Africa, were obtained for extraction with supercritical carbon dioxide. The effects of pressure and temperature on extraction yield were investigated. The total maximum yield of Marula kernel oil obtained was found to be 54 wt. %, compared to a solvent extracted yield of 52 wt. %, such that a 100 % oil recovery was obtained with SFE-CO2. The optimal conditions were found to be 450 bar and 60 °C as the yield per kg solvent initially was 41 g kg-1 CO2. Following the extractions, the oils were characterized for fatty acid composition using gas chromatography. Quality parameters of a cold pressed sample and a sample obtained at the optimal extraction conditions were determined and compared; and the results indicate that the two oils are of similar composition and quality. Supercritical fluid extraction using carbon dioxide was successfully verified as a potential processing method for the extraction of Marula oil from the kernels. The SFE-CO2 provided an improved yield compared to cold pressing and a quality of oil similar to cold pressed Marula oil. Additionally, after SFE-CO2 processing, the defatted Marula kernels contain high protein content, 69 wt. %, in the form of a pure white powder. Due to the favourable nutritional content the residue may be used for human consumption to create new products such as meat analogues, porridges, and shakes, or can be sold as a high protein powder. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2015