Evaluation of selected South African plant species for antioxidant, antiplatelet, and cytotoxic activity

The antioxidant, antiplatelet, and cytoxoxic effects of seven South African plant extracts, namely, Combretum vendae A. E. van Wyk (Combretaceae), Commiphora harveyi (Engl.) Engl. (Burseraceae), Khaya anthotheca (Welm.) C. DC (Meliaceae), Kirkia wilmsii Engl. (Kirkiaceae), Loxostylis alata A. Spreng. ex Rchb. (Anacardiaceae), Ochna natalitia (Meisn.) Walp. (Ochnaceae), and Protorhus longifolia (Bernh. Ex C. Krauss) Engl. (Anacardiaceae), were evaluated using established in vitro assays. All the extracts showed comparably low toxicity except for the extract of C. harveyi that showed high hemagluttination assay titer value, which indicates toxicity. The extracts of P. longifolia, K. wilmsii, O. natalitia, L. alata, C. harveyi, and C. vendae exhibited antioxidant properties in the qualitative assay using DPPH. In the quantification of antioxidation using ABTS, only the extracts of P. longifolia, L. alata, and C. vendae showed antioxidant activity with respective TEAC values of 1.39, 1.94, and 2.08. Similarly, in the quantitative DPPH assay, L. alata (EC50, 3.58 +/- 0.23 mu g/mL) and K. wilmsii (EC50, 3.57 +/- 0.41 mu g/mL) did not differ significantly (p <= 0.05) from the control. K. anthotheca showed a higher EC50 (176.40 +/- 26.56 mu g/mL) value, and differed significantly (p <= 0.05) from all the other extracts and control. In addition, the extracts of C. vendae and C. harveyi showed significant (p <= 0.05) antiplatelet activity and did not differ from the control (aspirin) with EC50 of 0.06 +/- 0.01 mu g/mL and 0.19 +/- 0.00 mu g/mL, respectively. Lower EC50 values in the antioxidant and antiplatelet studies are indicative of superior activity of the plant extract against oxidation and platelet aggregation.