Cytotoxic and Antioxidant Activities of Selected South African Medicinal Plants

Introduction: Indigenous plants are known to play a pivotal role in the well-being of Africa’s native societies. These plants are believed to be endowed with healing effects against various ailments rooting from oxidative stress. However, most of these plants including Ziziphus mucronata, Warburgia salutaris and Eucomis autumnalis lack scientific reports validating their medicinal properties. Thus, the current study, aimed to investigate the cytotoxic and antioxidant activities of selected South African medicinal plants. Methods: Scavenging activity of the extracts were evaluated on 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide anion (O₂ -) nitric oxide (NO-), hydroxyl anion (-OH) radicals and lipid peroxide (LP) values at varying concentration (20 - 100 μg/mL). Cytotoxic evaluation using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) was conducted on HEK293 cells. Reducing power and metal chelating ability of the extracts were assessed. In the same vein, protective index of DNA plasmid (pET151/D TOPO plasmid) induced free radical by incubating with Fenton’s reagents were tested, in vitro. Reducing and metal chelating ability of the extracts were evaluated in this study. Results: The crude extracts displayed radical scavenging activity and limit peroxidation process. The extracts showed potent ferric reducing power and chelating effects. Cytotoxic effects of the extracts analyzed using the MTT assay displayed low toxicity levels. Furthermore, the extracts were able to protect pET151/D-TOPO plasmid DNA nicking induced by hydroxyl radicals in a Fenton’s reaction mixture. Conclusion: It is evident in this study that the plant extracts are potential antioxidant therapeutics and justify inclusion of indigenous herbs as a complementary agents in the treatment regimen.