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    Antioxidant activities of ethanol extracts of Hypericum triquetrifolium and Hypericum scabroides
    (Taylor & Francis Ltd, 2008) Kizil, Goeksel; Kizil, Murat; Yavuz, Murat; Emen, Sevil; Hakimoglu, Fidan
    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 mu g/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 mu g 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.
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    Öğe
    Protective Ability of Ethanol Extracts of Hypericum scabroides Robson & Poulter and Hypericum triquetrifolium Turra against Protein Oxidation and DNA Damage
    (Korean Society Food Science & Technology-Kosfost, 2009) Kizil, Goeksel; Kizil, Murat; Ceken, Bircan
    The present study was conducted to determine the protective ability of the ethanol extracts of Hypericum scabroides Robson & Poulter (HS) and Hypericum triquetrifolium Turra (HT) against the protein oxidation and DNA damage induced by Fenton system. The ability of HS and HT to prevent oxidative damage to bovine serum albumin (BSA) induced by Fe3+/H2O2 and ascorbic acid was investigated. The ethanol extracts of HS and HT at different concentrations (50-1,000 mu g/mL) efficiently prevented protein oxidation induced by hydroxy radical as assayed by protein oxidation markers including protein carbonyl fort-nation (PCO) and polyacrylamide gel electrophoresis. The effect of ethanol extracts of HS and HT on DNA cleavage induced by UV-photholysis of H2O2 using pBluescript M13+ plasmid DNA were investigated. These extracts significantly inhibited DNA damage induced by reactive oxygen species (ROS). Therefore, HS and HT extracts may be useful in the food industry as effective synthetic antioxidants.