The protective effects of eugenol on carbon tetrachloride induced hepatotoxicity in rats

Our earlier studies in vitro have shown that eugenol inhibits liver microsomal monooxygenase activities and carbon tetrachloride (CCl4)-induced lipid peroxidation (Free Rad. Res. 20, 253-266, 1994). The objective of the present investigation was to study the in vivo protective effect of eugenol against CCl4 toxicity. Eugenol (5 or 25 mg/kg body wt) given orally for 3 consecutive days did not alter the levels of serum glutamic oxalacetic transaminase (SGOT), microsomal enzymes such as cytochrome P450 reductase, glucose-6-phosphatase (G-6-Pase) xenobiotic-metabolizing enzymes (aminopyrine-N-demethylase, N-nitrosodimethylamine-demethylase and ethoxyresorufin-O-deethylase) and liver histology. Doses of eugenol (5 or 25 mg/kg) administered intragastrically to each rat on three consecutive days i.e. 48 hr, 24 hr and 30 min before a single oral dose of CCl4 (2.5 ml/kg body wt) prevented the rise in SGOT level without appreciable improvement in morphological changes in liver. Eugenol pretreatment also did not influence the decrease in microsomal cytochrome P450 content, G-6-Pase and xenobiotic-metabolizing enzymes brought about by CCl4. Since eugenol is metabolized and cleared rapidly from the body, the dose schedule was modified in another experiment. Eugenol (0.2, 1.0, 5.0 or 25 mg/kg) when given thrice orally i.e. prior to (-1 hr) along with (0 hr) and after (+3 hr) the i.p. administration of CCl4 (0.4 ml/kg) prevented significantly the rise in SGOT activity as well as liver necrosis. The protective effect was more evident at 1 mg and 5 mg eugenol doses. However, the decrease in microsomal G-6-Pase activity by CCl4 treatment was not prevented by eugenol suggesting that the damage to endoplasmic reticulum is not protected. The protective effect of eugenol against CCl4 induced hepatotoxicity is more evident when it is given concurrently or soon after rather than much before CCl4 treatment.