Antioxidant activities of ethanol extracts of Hypericum triquetrifolium and Hypericum scabroides

Abstract

The antioxidative potential of ethanol extracts of Hypericum triquetrifolium Turra (Hypericaceae) and Hypericum scabroides Robson & Poulter (Hypericaceae) were investigated for the first time using 1,1-diphenyl-2-picrylhydrazyl (DPPH), metal chelating, reducing power, hydroxyl radical, total antioxidant activity, and lipid peroxidation inhibition assays. Both extracts tested were found to be highly active in the DPPH radical scavenging assay. The IC50 values of H. triquetrifolium (HT) and H. scabroides (HS) in the DPPH radical scavenging assay were 39.0 and 33.8 μg/mL, respectively. The amounts of total phenolic compounds were also determined, and total phenolic content of 1 mg H. triquetrifolium and H. scabroides ethanol extracts were equivalent to 267 and 333 μg gallic acid. Metal chelating ability was found to be low compared with EDTA. Both ethanol extracts of Hypericum species exhibited a high reducing power, suggesting that extracts had strong electron-donating capacity. The degradation of deoxyribose by hydroxyl radicals was shown to be inhibited by Hypericum extracts, acting mainly by scavenging hydroxyl radicals rather than as chelators of iron ions. Total antioxidant activity of ethanol extracts of HT and HS were tested by using ferric thiocyanate (FTC) and thiobarbituric acid (TBA) methods. Antioxidative activities of both extracts were found to be comparable with vitamin E. Moreover, both extracts showed notable capacity to suppress Fe2 +-induced lipid peroxidation in rat brain homogenate. The results obtained in the current study indicate that ethanol extracts of HS and HT are a potential source of natural antioxidants. © 2008 Informa Healthcare USA, Inc.