Free radical scavenging activity and phenolic contents of Anthocleista djalonensis (Loganiaceae) leaf extract

Abstract

Anthocleista djalonensis extract is widely used in Nigerian folk medicine to treat conditions whose pathogenesis implicate oxidative stress, such as diabetes and hepatitis. However, little is known of the mechanism underlying these activities. In this study, the free radical scavenging potential of a methanol extract of A. djalonensis leaves was assessed by measuring its capability for scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH.) radical, superoxide anion radical (O2.–), hydroxyl radical (.OH), nitric oxide radicals (NO.), as well as its ability to inhibit lipid peroxidation, using appropriate assay systems compared to natural and synthetic antioxidants. Total phenolic, flavonoid and flavonol contents were determined by spectrophotometric methods. This extract showed a very potent DPPH. and O2.– anion radical scavenging activities (IC50 = 8.69 ± 0.95 µg/ml and 5.32 ± 1.05 µg/ml respectively) and also significantly inhibited the accumulation of nitrite in vitro. The .OH radical and non-enzymatic lipid peroxidation inhibitory potentials of the extract were significantly higher (p0.05) than that of standard antioxidants (IC50 = 33.06 ± 5.65 µg/ml and 59.14 ± 4.64 µg/ml respectively). The plant extract yielded 0.989 ± 0.097 mg gallic acid equivalents phenolic content and 48.52 ± 1.10 mg rutin equivalents flavonoid content. The present study provides evidence that the methanol extract of A. djalonensis is a potential source of natural antioxidants. The observed antioxidant potentials of the extract suggest that it could impart health benefits when consumed. However, further investigation to verify its effect in vivo and isolate the active principles is warranted.