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Free-radicals have become a major source of health concern. The search for drug templates led to the screening of Acalypha ciliata, Acalypha hispida, Acalypha indica, Acalypha wilkesiana var. golden-yellow, Acalypha wilkesiana var. lace- acalypha, Acalypha wilkesiana var. red-acalypha, Centrosema procumbens, Centrosema pulmieri, Cyathula prostrata, Pycnanthus angolensis and Tridax procumbens for potential antioxidant activity. The plant extracts tested positive for initial rapid free-radical scavenging activity when sprayed with DPPH reagent. The extracts of A. ciliata, A. hispida, A. indica, A. wilkesiana var. golden-yellow, A. wilkesiana var. lace-acalypha and Tridax procumbens gave marginal antioxidant activity (IC50) of 0.65, 0.61, 0.72, 0.78, 0.76 and 0.67μg mL-1. However, C. prostrata and P. angolensis demonstrated remarkably moderate IC50 of 0.48 and 0.55 μg mL-1 respectively. The determined IC50 of C. prostrata was stronger than that of P. angolensis and compare favourably with the IC50 obtained for vitamin C at 0.45 μg mL-1. Furthermore, the determined IC50 values of C. prostrata and P. angolensis were better than those of vitamins A and E at 0.57 and 0.59 μg mL-1 respectively. The antioxidant activities given by the extracts were instructive because the phytochemical screening of the plants indicated the presence of terpenes, flavonoids and tannins which have been known to exhibit antioxidant activities. The results of the antioxidant assays have revealed C. prostrata and P. angolensis as potential plant templates which could be further investigated in detailed in-vitro and in-vivo studies for potentially safer and cheaper antioxidant drugs for the fight against destructive free-radicals.
Keywords: Free-radicals; antioxidant activity; DPPH reagent; C. prostrata; P. angolensis.