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

Abstract

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 µg/mL) and K. wilmsii (EC₅₀, 3.57 ± 0.41 µg/mL) did not differ significantly (p ≤ 0.05) from the control. K. anthotheca showed a higher EC₅₀ (176.40 ± 26.56 µg/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 µg/mL and 0.19 ± 0.00 µg/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.

Keywords::

• South African plants
• antioxidant assay
• antiplatelet activity
• cytotoxicity effect

Acknowledgements

The permission granted to us by the University of Pretoria Botanical Garden and the Lowveld National Botanical Garden, Nelspruit to collect the plant leaves is also greatly acknowledged.

Declaration of interest

We have acknowledged funds received from the SA-NRF for the study. The funds were provided to one of the authors (MM Suleiman) as PhD bursary at the University of Pretoria.