Comparative studies on antioxidant activities of extracts and fractions from the leaves and stem of Epimedium koreanum Nakai.

The antioxidant potency of various extracts and fractions from the leaves and stem of Epimedium koreanum Nakai was evaluated using three esteblished methods, specifically the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radica-scavenging activity assay, the inhibitory effect on lipid peroxidation induced by Fe(2+)/ascorbate (MDA) assay and the ferric reducing power (FRP) assay. The amounts of total phenolics and total flavonoids in the extracts and fractions were determined by spectrophotometric methods and the content of icariin was determined by HPLC. The results showed that all the extracts and fractions exhibited antioxidant activities at different magnitudes of potency. The leaf extract and fractions demonstrated superior antioxidant activity in most of the assays. The decreasing order of antioxidant activities among the extracts/fractions assayed through the three methods were found to be n-BuOH fraction>ethyl acetate fraction>ethanol extract>petroleum ether fraction>water fraction. A positive correlation was found between the amounts of total phenolics, total flavonoids and icariin and DPPH radical scavenging activity (R(2) = 0.9935, 0.9944 and 0.9997, respectively) and inhibitory activity on lipid peroxidation (R(2) = 0.9987, 0.9830 and 0.9886, respectively). The results suggested that Icariin was one of the main constituents contribute to the antioxidant activity of Epimedium koreanum Nakai and the n-BuOH fractions of leaf extract might be valuable antioxidant natural sources.