양파(Allium cepa) 추출물의 간보호 및 항산화 효과

Abstract

The objective of present study was to investigate the hepatoprotective and antioxidativeeffects of onion extracts. Primary cultures of rat hepatocytes were incubated with 1.5 mMtert-butyl hydroperoxide(t-BHP), potent oxidizing agent to liver, for 1 hr in the presence orabsence of various concentrations (0, 0.01, 0.05, 0.1 or 0.3 mg/ml) of onion extract.Incubation with t-BHP increased glutamic oxaloacetic transaminase(GOT) and lactatedehydrogenase(LDH) acitivities and thiobarbituric acid reactive substances(TBARS)concentration but decreased 3-(4,5-dimethylthiazol -2-yl)-2,5-diphenyl tetrazoliumbromide(MTT) reduction. Onion extracts at the concentration of 0.05 mg/ml decreased t-BHP-induced GOT and LDH activities. Onion extract at the concentration of 0.1 mg/mlincreased t-BHP-induced MTT reduction. Onion extract at the concentration of 0.01 mg/mldecreased t-BHP-induced TBARS concentration. Taken together, onion extracts preventedt-BHP-induced hepatocyte injury and lipid peroxidation. Catalase, glutathioneperoxidase(GSH-Px) and glutathione reductase(GSH-Rd) activities of hepatocytes weresignificantly decreased by t-BHP. Onion extracts at the concentration of 0.1 mg/mlprevented t-BHP-induced decrease in catalase, GSH-Px and GSH-Rd activities. Onionextracts prevented hydroxyl radical-induced single-strand breakage in dose-dependentmanner when plasmid DNA was incubated with various concentrations of onion extracts inthe presence of Fenton reagents producing hydroxyl radical. These results demonstrate thatonion extracts suppressed t-BHP-induced cytoctoxicity, decreased viability and lipidperoxidation and increased GSH-Px, GSH-Rd and catalase activities. Thus hepatoprotectiveand antioxidant effects of onion extract seem to be due to, at least in part, the increase inantioxidant enzyme activities as well as prevention from hydroxyl radical-induced oxidation,followed by inhibition of lipid peroxidation.