Determining the antimicrobial and anticancer potential of seven selected South African plants

Abstract

Different traditional cultures use traditional medicine to prevent, diagnose, improve, or treat illness. It is estimated that 80% of South Africans use traditional medicines as the primary care need and only few of South African medicinal plants have been exploited to their full potential in terms of commercialization. Varieties of phytochemicals (secondary metabolites) that may play a vital role on health improvement are found in plants. Healing and awareness of medicinal plants is an old practice. Thus, in search for treatment of human-related diseases, people used plants in nature as drugs. However, several challenges such as the safety, preparation methods and commercialization were faced. This has led to the search for antimicrobial, antioxidants and anticancer drugs from plant sources. In this study, aqueous and organic (ethanol) plant extracts of leaf and root of Bulbine frutescens, Bulbine natalensis, Chlorophytum comosum, Elytropappus rhinocerotis, Kniphofia uvaria, Tulbaghia violacea and corm of Hypoxis hemerocallidea were screened for antimicrobial, antioxidant and anticancer activities. For antimicrobial activity, plant extracts were screened against four microorganisms (Eschericia coli, Bacillus cereus, Aspergillus niger and Candida albicans). It was observed that shoots and roots of Bulbine frutescens, Bulbine natalensis and shoots of Chlorophytum comosum showed visible/clear zones of inhibition against E. coli, B. cereus and C. albicans, however other selected plant species showed no activity against tested microorganisms. For antioxidant activity, 2,2-diphenyl-l-picrylhydrazyl (DPPH) radical scavenging assay was used for the assessment of antioxidant activity of these selected plants. All plants were extracted with methanol and Trolox was used as the standard. E. rhinocerotis and H. Hemerocallidea showed the highest antioxidant activity of 115.22% and 114.88% respectively. For anticancer activity, the cytotoxicity effect of plant extracts (ethanol and aqueous) at final concentration of 100 μg/ml was assessed against human hepatocellular (HepG2), human colon (Caco-2) and human cervical (HeLa) cell lines using the MTT assay. The results showed that the ethanol extract of the plant materials exhibited high cytotoxicity against the three human cell lines, HepG2, Caco-2 and HeLa tested. The 100% ethanol extract of roots and shoots for all plant extracts displayed high activity against HepG2 compared to the 50% ethanol extract which indicated low anticancer activity. Moderate cytotoxicity was observed in the Caco-2 cell line for 50% ethanol extract. Aqueous extracts showed very little activity on all three human cell lines tested. In this study, it was concluded that antimicrobial, antioxidants and anticancer properties are present in the selected plant organs tested which, however, it warrants further study on the phytochemical properties.