Limited scientific data are available to validate the use of a variety of indigenous Nigerian plants to treat diseases whose pathogenesis implicates oxidative stress. We have, therefore, investigated the antioxidant ability, phenolic contents and cytotoxic effect of seven widely used Nigerian medicinal plants. Standard antioxidant assays were used to assess the capability of the extracts to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (.OH), superoxide anion (O2.-) radicals as well as to inhibit lipid peroxidation. Furthermore, the cytotoxic effect of the extracts on human peripheral blood mononuclear cells (PBMC) and A2.01 cell line was investigated ex vivo using 7-amino actinomycin and WST-1 cytotoxicity assay. The extracts possessed significant antioxidant activity compared to standard antioxidants, and had relatively low cytotoxicity. Landolphia owariensis and Irvingia gabonensis had the most potent antioxidant activity in the DPPH assay (IC50 = 8.8 ± 0.2 and 12.7 ± 0.4 μg/ml respectively) compared to ascorbic acid (4.9 ± 0.1 μg/ml) and also significantly inhibited the Fe2+/ascorbate-induced lipid peroxidation (IC50 = 31.9 ± 1.4 and 59.1 ± 1.6 μg/ml respectively). I. gabonensis and Nauclea latifolia were found to be powerful quenchers of .OH radical (IC50 = 25.5 ± 1.7 and 37.6 ± 4.7 μg/ml respectively) compared to α-tocopherol (IC50 =38.9 ± 2.8 μg/ml). The antioxidant activity and lipid peroxidation inhibitory potency of the plant extracts correlated significantly with their total phenolics and flavonoid contents. These results suggest that the inherent antioxidant activity of these extracts could be a substantial contributing factor to their traditional medicinal use.
Loading....