• Proceedings of the Plant Resources Society of Korea Conference
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• v.18 no.1
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• pp.52-60
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• 2005

The objectives of present study were to investigate the hepatoprotective and antioxidative effects of onion extracts. Primary cultures of rat hepatocytes were incubated with 1.5 mM tert-butyl hydroperoxide(t-BHP), potent oxidizing agent for liver injury for 1 hr in the presence or absence of various concentrations (0, 0.01, 0.05, 0.1 or 0.3 mg/ml) of onion extract. Cytotoxicity and cell viability were determined by measuring glutamic oxaloacetic transaminase(GOT) activity, lactate dehydrogenase(LDH) activity and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) value. Lipid peroxidation was evaluated using thiobarbituric acid reactive substances(TBARS) assay. Effects on antioxidant system were determined by measuring catalase, glutathione peroxidase(GSH-Px), glutathione reductase(GSH-Rd) activities as well as DNA strand breaking assay. Incubation with t-BHP alone increased GOT and LDH activities and TBARS concentration but decreased MTT reduction. Onion extracts at the concentration of 0.05 mg/ml began to decrease GOT and LDH activities induced by 1.5 mM t-BHP. Decreased MTT reduction began to be increased by onion extract at the concentration of 0.01 mg/ml. Onion extracts at the concentration of 0.01 mg/ml began to decrease TBARS concentration induced by t-BHP. Taken together, onion extracts prevented t-BHP-induced hepatocyte injury and lipid peroxidation. Catalase, GSH-Px and GSH-Rd activities of hepatocytes were significantly decreased by 1.5 mM t-BHP for 1 hr incubation. Onion extracts, on the other hand, at the concentration of 0.1 mg/ml began to prevent t-BHP-induced decrease in catalase, GSH-Px and GSH-Rd activities. Onion extracts prevented hydroxyl radical-induced single-strand breakage in dose-dependent manner when plasmid DNA was incubated with various concentrations of onion extracts in the presence of Fenton regents producing hydroxyl radical. These results demonstrate that onion extracts suppressed t-BHP-induced cytoctoxicity, decreased viability and lipid peroxidation and increased GSH-Px, GSH-Rd and catalase activities. Thus hepatoprotective and antioxidant effects of onion extract seem to be due to, at least in part, the increase in antioxidant enzyme activities as well as prevention from hydroxyl radical-induced oxidation, followed by inhibition in lipid peroxidation.