Free radical scavenging activity, phenolic contents and cytotoxicity of selected Nigerian medicinal plants

We investigated the antioxidant ability, phenolic contents and cytotoxic effects of seven widely edible Nigerian medicinal plants, as a means of validating their ethnomedicinal use. Standard antioxidant assays assessed the capability of the extracts in scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl ((OH)-O-center dot), and superoxide anion (O-2(center dot-)) radicals, as well as in inhibiting lipid peroxidation. The extracts possessed significant antioxidant activity compared to standards and the 7-amino actinomycin and WST-1 cytotoxicity assays proved that they were non-toxic to human peripheral blood mononuclear cells, and the A2.01 cell line. Landolphia owariensis and Irvingia gabonensis had the most antioxidant activity in the DPPH assay, compared to ascorbic acid. They also significantly inhibited lipid peroxidation. I. gabonensis and Nauclea lattfolia powerfully quenched the (OH)-O-center dot radical compared to alpha-tocopherol. The extracts' antioxidant activity and lipid peroxidation inhibitory potencies correlated with their phenolic and flavonoid contents. Thus, the antioxidant activities could be factors contributing substantially to their traditional medicinal use. (C) 2011 Published by Elsevier Ltd.