Browsing by Author "Marx, Jan-Taljaard"
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- ItemThe spatial and temporal effect on the phytochemicals of Dodonaea viscosa var. angustifolia (L.f.) Benth(Stellenbosch : Stellenbosch University, 2021-04) Marx, Jan-Taljaard; Makunga, Nokwanda Pearl; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.ENGLISH ABSTRACT: Dodonaea viscosa var. angustifolia is extremely polymorphic and has a worldwide distribution. It is an important traditional medicinal plant in South Africa, that has been used for centuries for its medicinal benefits. The knowledge regarding the metabolites responsible for the plant’s medicinal value is still limited. D. viscosa var. angustifolia has been shown to have antibacterial, antifungal and antioxidant potential. D. viscosa var. angustifolia flavonoids related to kaempferol and derivatives are thought to be some of the main compounds that contribute to the antioxidant activity of the species. Due to the natural medicinal value of the plant, there is potential to commercialize the extracts as an alternative treatment to modern medicine. Numerous communities are also still reliant on wild harvested medicinal plants as a more affordable option. It has been reported by the traditional healers in the Western Cape claim that certain areas and seasons yield greater medicinal potential. Due to the suggestion of a geographical and seasonal effect on D. viscosa var. angustifolia medicinal value and evidence in literature of geographical and seasonal effect on metabolite production, the idea of this study was to identify variation in significant compound production between season and geographical areas. D. viscosa var. angustifolia populations occur in very diverse environments and its well known that plants adapt their metabolite production to biotic and abiotic factors. The aim of this study was thus to determine if there was annual, seasonal and geographical variation in the chemical profile between different populations and whether certain environmental conditions lead to greater medicinal potential. D. viscosa var. angustifolia samples that were collected from Cederberg, De Hoop and Stellenbosch in the years, 2015, 2017 and 2019; and, chemical profiles were compared with each other. Samples gathered from the Cederberg, De Rust, De Hoop and Stellenbosch in winter, spring and summer were assessed and compared to determine if there was significant chemical variation between the populations and their respective seasons. The chemical profile of populations sampled in Kenya was also compared to South Africa populations, to further study the effect of geographical variation. Furthermore, the effect of the soil’s chemical profile on the chemical profile of D. viscosa var. angustifolia was also studied and the potential of stored samples to retain their antioxidant potential. All the sample extract data were obtained via liquid chromatography-mass spectrometry (LC-MS) before the application of a non- targeted and semi-targeted metabolomics approaches to determine chemotypic differences amongst test phytoextracts. From the South Africa populations 10 individuals were sampled per locality, season and year. For the Kenya populations, 3 individuals were sampled with 3 replicates. In total 35 chemicals were tentatively identified by comparing literature of spectral data and online metabolomics with the obtained intensity, retention time, chromatogram peak and their respective MSE ion fragmentation data of D. viscosa var. angustifolia. Based on the principal component analysis (PCA) for the year comparison, the 2019 population clusters all grouped together, while the 2015 and 2017 populations indicated some overlap. For the seasonal comparison, the De Rust population formed isolated clusters for each season, with no overlap between the other populations. The multifactorial analysis also indicated that the soil chemical profile did not have a significant effect on the metabolite profile of D. viscosa var. angustifolia (p = 0.93). From the partial-least- squares discriminant analysis (PLS-DA) each Kenya population formed its own unique cluster and only the Stellenbosch population formed a sperate cluster with no overlap occurring between the other South African populations. Therefore, most populations formed their own unique clusters and the respective heatmaps elucidate on which compounds contributed to the unique cluster formations. Some of the medicinal compounds compared in each chapter were pinocembrin, rhamnocitrin and santin. The production of pinocembrin remained constant between the years occurring at a relative intensity value of 252.43, with significant decline only found from the year 2015 to 2017 in the Cederberg population (p < 0.01). The Cederberg 2019 population produced significantly more pinocembrin than the other South Africa populations (p < 0.01). The production of pinocembrin, occurring at a relative intensity value of 211.56, did not differ significantly between seasons. It was apparent in the Kenya and South Africa comparison that the production of pinocembrin was significantly more in Nanyuki, Narok and the Cederberg populations (p < 0.01). Between seasons and across years the production of rhamnocitrin did not differ significantly, however, it was found that Narok and Nairobi produced significantly more rhamnocitrin (p < 0.01) than the other populations. The production of santin also did not vary across years or between seasons, but the Nanyuki and Narok plants had significantly more santin (p < 0.01) than the other populations. Overall, it was evident that the metabolite production of several compounds differs between years, seasons and geographical region. This signifies that D. viscosa var. angustifolia is robust in maintaining some of its medicinal properties between seasons and across years, and highlights that geographical region has a substantial effect on its medicinal efficacy. This indicates that the genetic constituents should be prioritized for the commercialization or cultivation of D. viscosa var. angustifolia and that climate conditions and seasonal variation will not severely affect its potential as a phytomedicine. Promoting the cultivation of D. viscosa var. angustifolia would thus preserve wild populations and promote further genetic diversity, which can lead to greater sustainable exploitation of this species for future generations.