Effect of Onion Extract on the Carbon Tetrachloride-induced Liver Injury in Mouse

Abstract

The protective effects of onion extract (OE), onion powder extracted in ethanol for 2 days, on carbon tetrachloride (CCl₄)-induced hepatotoxicities, the possible mechanisms involved in this protection were investigated in mice. Pretreatment with OE prior to the administration of CCl₄ significantly reduced the increase in serum alanine, aspartate aminotransferase activities, hepatic lipid peroxidation in a dose-dependent manner. In addition, pretreatment with OE significantly prevented the depletion of reduced glutathione content in the liver of CCl₄-intoxicated mice. CCl₄-induced hepatotoxicity was also prevented, as indicated by a liver histopathologic findings. The effects of OE on the cytochrome P450 (P450) 2E1, the major isozyme involved in CCl₄ biotransformation were investigated. Treatment of mice with OE resulted in a significant decrease in P450 2E1-dependent p-nitrophenol, aniline hydroxylation in a dose-dependent manner. Consistent with these observations, the P450 2E1 expressions were also decreased, as determined by immunoblot analysis. OE also exhibited antioxidant effects in FeCl₂-ascorbate induced lipid peroxidation in rat liver homogenates, in superoxide radical scavenging activity. These results show that the protective effects of OE against the CCl₄-induced hepatotoxicity may be due to its ability to block bioactivation of CCl₄, mainly by inhibiting the expression, activities of P450 2E1, by scavenging free radicals.