Hepatoprotective effects of purified oleuropein from olive leaf extract against ethanol-induced damages in the rat

Summary Olives and olive oil contain large amounts of oleuropein. This phenolic compound is responsible for their bitter taste and pungent aroma and has been recognized as a powerful hypotensive, hypoglycemic and antioxidant agent. Thus, the aim of the present study was to evaluate the antioxidant properties of oleuropein on ethanol-induced oxidative damage and to examine its beneficial effects on liver function. Thirty-two adult male Sprague-Dawley rats were divided into four equal groups: the first group served as untreated control. The second group of rats were given ethanol (4 g/kg) orally. Group 3 received oral oleuropein (15 mg/kg). The final group of rats were fed ethanol (4 g/kg), 120 min after oral administration of oleuropein (15 mg/kg). All of the treatments were applied for 4 weeks via gavage. Administration of ethanol to rats induced toxicity in their liver, as shown by the significant elevation in the serum levels of transaminases, total cholesterol as well as liver histopathological findings. Elevation of glutathione peroxidase activity, the hepatic main antioxidant enzyme, and total glutathione was observed to suppress oxidative stress in the ethanol group. TBARS (an indicator of lipid peroxidation) concentration is also increased in ethanol-treated rats. In contrast, oleuropein during ethanol treatment in rats resulted in a higher antiperoxidative enzyme activity, catalase, and inhibited toxicity to the liver, as monitored by the reduction in ALT and AST levels and TBARS concentration. It is suggested that oleuropein possesses beneficial antioxidant effects against ethanol-induced liver toxicity, and therefore use of olive leaf extract may have prophylactic value in reducing the common complications resulting from oxidative stress in alcoholism.