Chemopreventive activity of very low dose dietary tannic acid administration in hepatoma bearing C3H male mice

Tannins are plant polyphenols comprising a heterogeneous group of compounds . Tannic acid is a common tannin found in tea, coffee, immature fruits, etc . and it has also been used as a food additive. An increasing body of exper imental evidence supports the hypothesis that tannins exert anticarcinogeni c activity in chemically induced cancers in animal models. in the present s tudy, tannic acid was administered in very low doses in the drinking water of C3H male mice divided into three groups (75 mg/l, 150 mg/l and 300 mg/l) , These animals carry a genetic defect and show a high incidence of spontan eous liver tumors ( > 50%) at an age older than 12 months. The results show ed a decrease in the overall incidence of hepatic neoplasms (adenomas plus carcinomas): 53.3% of animals in the control group developed hepatic neopla sms Versus 33.3% in the group given a low dose of tannic acid 26.6% in the group given a medium dose and 13.3% in the high dosage group. The differenc e was more pronounced in the animals with carcinomas: 4.44% of mice who rec eived tannic acid developed carcinomas versus 33.3% of those in the control group. Tannic acid administration did not affect the PCNA labeling index o f normal hepatocytes. It is concluded that tannic acid dietary intake in lo w doses can exert a strong dose-dependent chemoprotective activity against spontaneous hepatic neoplasm development in C3H male mice, most probably th rough antipromoting mechanisms. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.