School of Animal, Plant and Environmental Sciences (ETDs)

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Browsing School of Animal, Plant and Environmental Sciences (ETDs) by Author "Basson, Domonique Courtney"

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    The effects of elevated carbon dioxide concentrations on the physiological and biological characteristics of Portulacaria afra
    (University of the Witwatersrand, Johannesburg, 2024) Basson, Domonique Courtney; Risenga, Ida
    There is a concern that rising atmospheric carbon dioxide (CO₂) concentrations may affect the medicinal or nutritional profile of medicinal plants. Portulacaria afra (P. afra) is a medicinal plant used by traditional healers to treat various skin conditions. The aim of this study was to determine whether elevated CO2 concentrations will affect the physiological and medicinal properties of the leaves, stems, and roots of P. afra. This was achieved by measuring the physiological, phytochemical, antioxidant, and antimicrobial activity of the various plant parts, which were exposed to ambient (420 ppm) and elevated (600 ppm) CO₂ concentrations and comparing them to samples grown in greenhouse conditions. The plant samples were placed in a Conviron climate stimulator for three months. Three harvests were completed during thistime. The physiological properties measured include the weight of the various plant parts as well as the chlorophyll content within the leaves. The phytochemical profile of the plant was examined through a set of standard colour tests (qualitative analysis) and the determination of the total flavonoid content (quantitative analysis) in all three plant parts exposed to the various treatments. The antioxidant activity was determined by analysing the scavenging activity of the extracts against 1,1 diphenyl-2- picrylhydrazel (DPPH) and hydrogen peroxide (H2O2) with the use of a spectrophotometer. The antimicrobial activity determined the extracts’ ability to inhibit the growth of six microorganisms related to skin conditions. The results of this study revealed that there was a 65% and 39% increase in the weight of the leaves and roots, which were exposed to 600 ppm, respectively. A higher phytochemical presence was recorded in plants exposed to 600 ppm. There was a significant increase in flavonoid presence and flavonoid content in the methanolic and hot water plant samples that were exposed to elevated CO2.The leaves, stems, and roots of P. afra exhibit strong scavenging activity against DPPH and even more so towards H2O2. The strongest antioxidant activity was 13 exhibited by the methanolic leaf extracts which were exposed to 600 ppm, against H2O2 (0.2±0.7 mg/ml). The antimicrobial activity of all three plant parts was relatively constant between the different treatments. Despite the relatively weak antimicrobial activity of P. afra (MIC values > 1000 (µg/ml), a notable increase in the antimicrobial activity of the leaves against Cutibacterium. acnes were observed in samples exposed to 600 ppm of CO₂. Portulacaria afra is a medicinal plant that exhibits great resilience towards elevated atmospheric CO2 concentrations. The phytochemical and biological properties in this study displayed either no change or an increase in activity, which suggests that P. afra may continue to provide relief against certain ailments in the future despite rising atmospheric CO2 concentrations