Preventive effect of tannic acid on 2-acetylaminofluorene induced antioxidant level, tumor promotion and hepatotoxicity: a chemopreventive study.

Tannic acid, present in almost every food derived from plants, has been widely investigated as a chemopreventive agent because, apart from its use as a food additive, pharmacological studies have demonstrated its many health-promoting properties. In this study, we show the modulatory effect of tannic acid on 2-acetylaminofluorene (2-AAF)-mediated hepatic oxidative stress and cell proliferation in rats. 2-AAF (50 mg/kg body weight) caused reduction in hepatic glutathione content and the activities of hepatic anti-oxidant enzymes and phase-II metabolizing enzymes with an enhancement of xanthine oxidase activity, lipid peroxidation and hydrogen peroxide content. 2-AAF treatment also induced serum oxaloacetate and pyruvate transaminase, lactate dehydrogenase and gamma-glutamyl transpeptidase. Treatment of rats orally with tannic acid (125 and 250 mg/kg body weight) resulted in significant recovery of hepatic glutathione content, antioxidant and phase-II metabolizing enzymes. Also, significant decreases in lipid peroxidation, xanthine oxidase, hydrogen peroxide generation and liver damage marker enzymes were observed. The antiproliferative efficacy of the tannic acid was also evaluated. The promotion parameters induced (ornithine decarboxylase activity and DNA synthesis) by 2-AAF administration in the diet with partial hepatectomy (PH) were also significantly suppressed, dose dependently, by tannic acid. Hence, we propose that tannic acid might suppress the promotion stage via inhibition of oxidative stress and polyamine biosynthetic pathway.