Abstract

Anisopus mannii (Asclepiadaceae) –a plant widely used as an anti-diabetic agent in Northern Nigerian traditional medicine, was subjected to antioxidant evaluation. The crude methanol extract, n-butanol and ethyl acetate fractions were investigated for free radical scavenging activity of the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH), total phenolic contents and reducing power assay. The results of the DPPH free radical scavenging at 250 µgml^-1 indicated maximum antioxidant activity of 94.1, 94.3 and 88.7% for crude methanol extract, ethyl acetate and n-butanol fractions, respectively. The total phenolic content was higher in the ethyl acetate fraction (59.60 mg/g gallic acid equivalent GAE) than in the n-butanol fraction (56.40 mg/g GAE) and crude methanol extract (53.20 mg/g GAE). The reducing power of n-butanol fraction was 0.112 nm higher than those of ethyl acetate fraction (0.110 nm) and crude methanol extract (0.106 nm). The antioxidant activities of the crude extract/fractions and the standards at maximum concentration of 250 µgml^-1decreased in the order: ascorbic acid> ethyl acetate fraction> crude methanol extract> Gallic acid> n-butanol fraction, but there was no significant difference (p < 0.05) between them. The phytochemical screening revealed the presence of flavonoids, tannins and saponins. This suggests a potential utility of the plant as a source of phenolic antioxidants and may provide leads in the ongoing search for natural antioxidants from Nigerian medicinal plants to be used in treating diseases related to free radical reactions.

Key words: Anisopus mannii, antioxidants, 1, 1-diphenyl-2-picrylhydrazyl radical, reductive potential, total phenolic contents.