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

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 syntheticantioxidants. 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 ìg/ml and 5.32 ± 1.05 ìg/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 (