School of Animal, Plant and Environmental Sciences (ETDs)

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Browsing School of Animal, Plant and Environmental Sciences (ETDs) by SDG "SDG-3: Good health and well-being"

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    An ethnobotanical study of indigenous knowledge of the medicinal plants used by traditional healers in the rural communities of Nkomazi Local Municipality, Mpumalanga province
    (University of the Witwatersrand, Johannesburg, 2024) Khoza, Nompendulo; Dukhan, Shalini; Ramalepe, Phillemon; Risenga, Ida
    Traditional medicine continues to significantly impact many people’s lives amid all the advancements in modern medicine. Many rural communities in Mpumalanga province depend on indigenous traditional medicines to manage various ailments. The available research on the traditional usage of medicinal plants among rural communities in Mpumalanga is highly fragmented and under-researched. The decline of medicinal plant populations has led stakeholders to take various initiatives to counteract over-exploitation, including cultivation as a viable conservation approach. However, the scientists' inadequate understanding of the acceptance of cultivated medicinal plants by traditional healers is one of the issues contributing to the failure of medicinal plant cultivation programs. Consequently, this study aimed to document medicinal plants utilised by the Nkomazi Local Municipality's traditional healers and assess opportunities and constraints for medicinal plant conservation in the Nkomazi Local Municipality. The ethnobotanical data was obtained through semi-structured questionnaires and guided field walks with traditional healers. Individual interviews were conducted with ten traditional healers from eight villages across Nkomazi during field visits between July 2021 and February 2022. The study employed qualitative and quantitative approaches to understand traditional healers' perspectives concerning the ethnobotanical significance and medicinal plant conservation. The study found that the indigenous knowledge of medicinal plants in the Nkomazi Local Municipality is diverse, encompassing 111 species from 59 different families employed to treat 70 ailments. Most of the reported medicinal plants for this study are of Least Concern. Additionally, the top fourteen most reported species in the Nkomazi Local Municipality included commercially valuable plants such as Psidium guajava, Ricinus communis, Sclerocarya birrea, Aloe ferox, Aloe maculata, Leonotis leonurus, and Moringa oleifera. Most of the Nkomazi Local Municipality's traditional healers did not know about protected plant species and the National Environmental Management Act (NEMA). Traditional healers were aware of the decline in wild populations of medicinal plants, which they attributed to various factors such as overharvesting. Diviner’s and herbalist perception of using cultivated plants did not differ significantly (𝜒2=0.4762, df=1, P= 0. 490). The study provided a comprehensive inventory of medicinal plants utilised by Nkomazi traditional healers and essential data for future assessments of the use local use of indigenous medicinal plants.
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    The effects of elevated carbon dioxide on the secondary metabolites and biological activities in Moringa oleifera Lam. and Moringa peregrina Forssk
    (University of the Witwatersrand, Johannesburg, 2023) Moloi, Thato; Dukhan, Shalini; Ramalepe, Phillemon; Risenga, Ida
    Climate is crucial for the distribution and survival of medicinal plants as it can influence phytochemicals and regulatory hormones that are responsible for the normal growth and development, as well as their interactions with the environment. Thus, it is important to understand how climate change will impact these crucial plant compounds and hormones that play a significant role in the plant’s survival and development. With the increasing CO2 in the atmosphere, it is expected that climate change effects will be devastating to the world and Southern Africa. The present study intended to achieve two aims, the first being to investigate the impacts of elevated CO2 (eCO2) on the secondary metabolites and biological activities of two important Moringa species, Moringa oleifera Lam. (M. oleifera) and Moringa peregrina - (Forssk.) Fiori (M. peregrina). The second aim was to investigate how the use of M. oleifera leaf extract (MLE) based and commercial (PhytoStim®) biostimulants influence the productivity as well as the adaptability of M. oleifera and M. peregrina under elevated eCO2. The first set of three-month-old potted plant samples were exposed to 400 ppm (control), 600 ppm and 800 ppm for three months, respectively. The second set of plants were placed in the greenhouse and sprayed (foliar application) with 200 mL of M. oleifera leaf extract (MLE) and 200 mL commercial biostimulant PhytoStim® every second week for three months, respectively. The control samples were unsprayed. The third set of plants were exposed 600 ppm and 800 ppm (separately) and simultaneously sprayed with 200 mL of M oleifera leaf extract (MLE) and 200 mL commercial PhytoStim® (separately) every second week for three months to assess the influence of biostimulants on the adaptability of the Moringa species under eCO2. The control samples under 400 ppm were unsprayed. In this study, 80% methanolic extracts from all the above mentioned treatments of M. oleifera and M. peregrina were screened for 17 secondary metabolite groups (tannins, saponins, flavonoids, quinones, phenols, terpenoids, cardiac glycosides, coumarins, steroids, phlobatannins, anthracyanine, volatile oils, phytosterols, triterpenoids, proteins and amino acid, glycosides, carbohydrates) using qualitative methods. Quantitative analyses were performed to determine the total phenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC) and total proanthocyanidin content (TPAC). The antioxidant assays were performed to determine the reducing, scavenging and chelating abilities against DPPH, H2O2 and metal (Iron) chelating. The antimicrobial activities against gram negative Escherichia coli and gram-positive Staphylococcus aureus, Streptomyces albulus were assessed by using the agar well diffusion assay. In the control samples, out of 17 screened secondary metabolites, four (phytosterols, volatile oils, anthocyanin and phlobatannins) were not detected in both species’ extracts. On average, M. peregrina showed higher total content of tannins, phenolics, flavonoids and proanthocyanidins. M. peregrina showed stronger antioxidant activity against iron chelating and H2O2, whilst M. oleifera showed stronger antioxidant activity against DPPH. Both M. oleifera and M. peregrina extracts displayed an acceptable bacterial growth inhibition capability (ZOI ≥10 mm) with only S. albulus being resistant to the control of M. oleifera. Qualitative phytochemical analysis indicated the presence of secondary metabolites such as tannins, saponins, flavonoids under 600 ppm and a slight decline under 800 ppm in both species. The quantitative analysis indicated an increase in the total content of phenols, flavonoids (flavanols), tannins, and proanthocyanidins. An increase in CO2 resulted in an increase in the activity of antioxidants and antibacterial for both species. On average, Moringa peregrina showed higher accumulation of secondary metabolites, higher antioxidant and antibacterial activities in comparison to Moringa oleifera. The foliar application of MLE and PhytoStim® showed an increase in some secondary metabolites and decrease in metabolites such as tannins and phenols in M. oleifera. The application of biostimulants (MLE and PhytoStim®) also resulted in an increase in TPC, TTC and TPAC in M. peregrina, with a decline in total contents of these compounds in M. oleifera. However, the decline did not negatively impact both species' pharmacological abilities (antioxidant and antimicrobial activities), as they exhibited stronger antioxidant and antimicrobial activities when compared to the untreated plants (control samples). The use of the above mentioned plant based biostimulants resulted in an enhanced adaptability as indicated by the increase in the accumulation of selected screened secondary metabolites plant samples that exhibited signs of stress. The higher accumulation of secondary metabolites was observed under 600 ppm, in combination with PhytoStim® for either species. The combined CO2 and biostimulant treatments improved the total phenolic content (TPC) of both M. oleifera and M. peregrina significantly, with M. oleifera showing higher TPC content when compared to M. peregrina. On average, both M. oleifera and M. peregrina exhibited lower total flavonoid content (TFC), total tannin content (TTC) and total proanthocyanidins (TPAC), with M. oleifera showing higher contents of the above-mentioned phytochemicals in comparison to M. peregrina. The study also highlighted a decline in biological activities for all treatments, with the controls showing higher biological activities for both species. In the three antioxidant assays conducted, the leaf extracts of the controls had significant lower IC50 values for DPPH and H2O2, when compared to the stressed M. oleifera and M. peregrina. Antimicrobial assays also showed no significant difference in the bacterial inhibition capabilities of M. peregrina and M. oleifera under 600 ppm and 800 ppm with either biostimulant application. M. peregrina and M. oleifera controls showed high ZOI for the selected bacterium. The study has demostrated that biostimulants (MLE and PhytoStim®) enhanced the adaptability of both species under potential stress coursed by eCO2. The present study has demonstrated that the exposure to elevated CO2 could alter the accumulation and biological processes (such as antioxidant activity and antimicrobial activity) in both M. oleifera and M. peregrina. Moringa peregrina exhibited more tolerance to elevated CO2 when compared to Moringa oleifera and showed higher antioxidant and antimicrobial activity which might be attributed to the stronger presence of phytochemicals such as flavonoids, phenols and tannins. The data also suggests that both Moringa oleifera and M. peregrina can adapt to high levels of CO2 concentrations (~600 ppm), however, as medicinal plants, it might be difficult to sustain the acclimatisation and tolerance due to membrane oxidation and DNA damage. Therefore, foliar application of the biostimulants could enhance the adaptability and productivity of both species under high levels of CO2. This study may contribute towards better planning on conservation efforts to improve the chances of survival of the Moringa oleifera and M. peregrina and could aid with food security.
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    The Impact of different levels of organic plant-based compost on the macro and micro elements, secondary metabolites and water soluble vitamins content of Moringa oleifera leaves
    (University of the Witwatersrand, Johannesburg, 2023) Ngwenya, Nkazimulo; Risenga, Ida M.; Chimuka, Luke
    Moringa oleifera leaves are a high source of phytochemicals and nutrients inclusive of macro and micro elements, secondary metabolites and water-soluble vitamins. All the M. oleifera plant parts inclusive of its leaves have been widely utilised for nutritional and/ medicinal properties because of its high levels of minerals and phytochemicals. Studies have been conducted targeting the improvement of the quantity of M. oleifera nutrient content. However, with increased consumer awareness of high quality organic, consumer and environmentally safe products there is increased need to improve the quality of M. oleifera products. One of the major factors impacting the quality and quantity of M. oleifera leaf nutrients is cultivation practices. Particularly soil amendments applied to improve plant biomass have also been found to significantly improve nutrient content of M. oleifera leaves. However, the popularly used soil amendments which are in the form of synthetic fertilisers or animal based compost have raised environmental and product safety concerns. They contain, among other contaminants, traces of heavy metals and other toxins which are harmful to both the environment and consumers of the produce. Producers of herbal plants such as M. oleifera are looking for sustainable, environmental safe ways of improving the quantity and quality of the produce. Application of organic plant based compost was therefore investigated as a potential soil amendment source in improving M. oleifera nutrients in an organic, clean sustainable way, and thus improving the quality of the produce. The use of plant based compost to improve the nutritional content of M. oleifera grown in South Africa was reported in this thesis. The primary objective of the study was to assess the impact of the plant-based organic compost on the macro and micro elements composition, secondary metabolite accumulation and distribution and water soluble vitamins content in M. oleifera leaves. This work is novel and worth exploring as it seeks to investigate for the first time the correlation between the use of plant-based organic compost and quality improvement in terms of nutrient content of M. oleifera leaf biomass. Furthermore, this research is the first of its kind which looks at the impact of compost on the nutritional content encompassing, macro and micro nutrients, secondary metabolites and water soluble vitamins in M. oleifera grown in South Africa. In addition, the developed and validated high performance liquid chromatography (HPLC) method for the simultaneous quantification of five B vitamins was successfully used in the identification and quantification of the vitamins. Clay soil and M. oleifera seeds used in the study were obtained from the M. oleifera community farm in Hammanskraal, Gauteng, South Africa. The clay soil was amended with plant-based organic compost purchased from the local nursery store. The amendments achieved four treatment levels namely 15 % compost / soil amendment, 30 % compost / soil amendment, 45 % compost / soil amendment and 60 % compost / soil amendment. Moringa oleifera seeds used were obtained from the same farm. Plant samples were grown in the School of Animal, Plant and Environmental Sciences (APES), University of the Witwatersrand, greenhouse under ambient temperatures. Harvesting of the leaf biomass was done after six months and nutrient analysis was carried out. Analytical techniques such as Spectroscopy and Chromatography were used for the nutrient analysis. Presence and quantity of macro and micro elements in the soil and leaves was analysed using the Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). Whilst, the Ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESI-QTOF-MS) was used to determine plant metabolites, and for the quantification of water-soluble vitamins by coupling it with the diode array detector (DAD). The nutrient analysis revealed that the use of organic plant-based compost for the amendment of clay soil improved the quality of the soil and M. oleifera leaves harvested from each soil amendment. The addition of the organic plant-based compost improved the macro and micro nutrients. Comparison of the different compost levels revealed that addition of plant based compost increased the bioavailability of macro and micro nutrients in the soil and increased their accumulation in M. oleifera leaves. Metabolic fingerprinting of M. oleifera leaf samples using UHPLC-ESI-QTOF-MS followed by untargeted compound analysis exposed variation in the identified metabolites. Further use of multivariate analysis in the form of PCA clustered the samples into five distinct clusters indicating diversity in the distribution of secondary metabolite as influenced by the addition of plant-based compost to the soil. The developed HPLC method was suitable for the simultaneous quantification of five B vitamins based on the low LOD and LOQ values, recovery of 97.8- 99.58% and good linearity. Application of the validated method revealed that, the addition of plant based compost significantly improved the quantity of the tested vitamins (Vitamin B1, B2, B3, B6 and B9). The 30% plant-based organic compost and clay soil combination was identified and recommended as the best compost-soil combination in improving nutrients in M. oleifera leaf biomass. It had the highest level of macro and micro nutrients. Leaves harvested from this soil/compost combination had higher concentration of Ca (45 042.5 mg/Kg), Mg (17 430 mg/Kg), P (8802. 5 mg/Kg). In addition leaves, harvested from 30% compost treatment exhibited the highest number of identified secondary metabolites and had the highest concentration of two of the five tested water soluble vitamins. This knowledge will make great contribution in the M. oleifera industry in South Africa and worldwide particularly for farmers who are into organic M. oleifera production.
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    Uncovering genetic changes underlying adaptation in southern African dwarf chameleons (Bradypodion)
    (University of the Witwatersrand, Johannesburg, 2024) Taft, Jody M.; Alexander, Graham J.
    Natural selection acting on the available range of phenotypes in a population will favour alleles beneficial to an organism’s fitness, resulting in adaptation. Characterizing patterns of adaptive genetic variation in wild populations is a fundamental first step toward understanding the potential for adaptation in response to selection. With recent advances in sequencing technology, the increased availability of high-quality genomic resources has made efforts to identify loci under selection across the genome more tractable. As a result, there is a growing body of research challenging the notion that adaption takes place over deep evolutionary timescales, with evidence of rapid adaptation occurring in a range of taxa. Examples of rapid adaptation are rife within reptiles, particularly in response to contemporary environmental changes such as urbanization. Despite this, insights into the genetic architecture of adaptation in reptiles remain limited as appropriate genomic resources are currently lacking. The southern African dwarf chameleons, Bradypodion, are the most recently diverged lineage in Chamaeleonidae. These arboreal lizards are well known for their high capacity for adaptation, especially in response to environmental change. Bradypodion are known to have undergone rapid diversification linked to habitat specialization resulting in the emergence of few convergent phenotypes, or ecomorphs, across the genus. These lizards occupy a variety of habitat types, from closed-canopy forests to open-canopy habitats such as grasslands, but are also known to occur within urban environments. As ecomorphs of various Bradypodion species display phenotypic convergence in similar habitat types, populations may also converge phenotypically in urban habitats. However, the underlying genetic architecture of these phenotypes remains unknown for Bradypodion, further constrained given the absence of appropriate genomic resources for these lizards. To facilitate insights into the genetic architecture underlying adaptation in Bradypodion, two de novo assembled whole genomes were produced using Pacific Biosciences long-read sequencing data. These assemblies are among the highest-quality squamate genomes published to date. In addition, coalescent analyses of these assemblies indicated that historical changes in effective population size correspond to notable shifts in the southern African environment. Furthermore, the high-quality annotations of both Bradypodion genome assemblies were generated and used to describe the genetic feature landscapes and evaluate the gene family evolution of Bradypodion. Findings indicated that expanded gene families within this genus are likely the result of responses to changing environmental conditions, facilitating the diversification of Bradypodion. In addition, differences in gene family composition at the species level provide insights into underlying genetic pathways resulting in adaptive traits possibly promoting ecomorph divergence across the genus. Lastly, to detect loci under selection, population structure and genetic diversity were assessed in five species of Bradypodion known to have populations in natural and urban habitats using a pairwise comparative approach. While there is evidence of allele frequency differentiation between urban and natural populations, it is uncertain that this is due to selection pressures experienced by the urban population. While links between genes containing outlier loci and the phenotypic traits known to be associated with adaptation in urban habitats are made, it is recommended that these genes be used as candidates for targeted gene modification to evaluate the phenotypes generated by those modifications and contrasted with phenotypes present in urban populations. This thesis provides insights into the mechanistic genomic basis of adaption in Bradypodion. The high-quality genomes and annotations produced here will hopefully serve as a resource for further assessments of genetic adaptation in chameleons and reptiles more broadly. Furthermore, these findings present a framework from which to formulate robust hypotheses to assess candidate genes presented here as likely underlying adaptive phenotypes in urban populations