Antioxidant and hepatoprotective potentials of olive (Olea europaea L. var. Sigoise) leaves against carbon tetrachloride-induced hepatic damage in rats, and investigation of its constituents by high-performance liquid chromatography-mass spectrometry

The present work explored the preventive potential of ethanolic extract of Olea europaea L. (EEOE) leaves against CCl4-induced liver injury in rats. The fingerprint chromatogram of EEOE was determined by HPLC-MS analysis. The antioxidative potential of EEOE was determined by adopting three approved in vitro methods. The EEOE was orally given at a dose of 400 mg/kg, once a day, for 15 days continuously, succeeded by intraperitoneal (i.p.) injection of CCl4 (0.2%). The hepatoprotective potential was evaluated by estimating biochemical parameters including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, total cholesterol, and triglycerides in the bloodstream. In vivo, the antioxidant ability against CCl4-induced liver injury in rats was assessed by estimating the levels of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total reduced glutathione, and lipid peroxidation in the liver tissues. Further, histological analyses were performed to evaluate the degree of hepatic damage. Nine compounds were identified in the EEOE, principally oleuropein, luteolin-7-O-glucoside, and apigenin. The EEOE exhibited strong radical scavenging activity in DPPH assay. The EEOE significantly decreased the augmentation of serum cholesterol, TG, ALT, AST, ALP, and total bilirubin contents. It also restored hepatic SOD, CAT, GSH-Px activities, and glutathione (GSH) amount, and lowered lipid peroxidation amount comparable to the standard silymarin. The biochemical data were complemented with histological conclusions. These findings are indicative of the protective potential of the EEOE against CCl4-induced hepatotoxicity, which is possibly related to the potent antioxidative capacity of its phenolic compounds.