Antioxidant activity of Knipholone anthrone

Knipholone anthrone (KA), isolated from an Ethiopian medicinal plant, Kniphofia foliosa, Hochst (Asphodelaceae) has been shown to display a potent antiprotozoal activity and a relatively little cytotoxic effect on mammalin cells. In the present study, the antioxidant potential of KA was assessed using a variety of in vitro assay models. KA displayed a concentration-dependant scavenging effect against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The IC50 values obtained for KA and the positive control (−)-epicatechin (EC) in the DPPH assay were 22 ± 1.5 and 8.7 ± 0.9 μM (mean ± SEM; n = 3 separate experiments), respectively. KA displayed a better activity than EC in scavenging superoxide anions and preventing deoxyribose degradation by hydroxyl radicals. KA appeared to form a complex with Fe2+, displayed a concentration-dependant reducing power, and also protected (at concentrations of 4.4 μM and above) isolated DNA from damage induced by Fenton reaction-generated hydroxyl radicals.