Inhibitory effect of tannic acid on iron–dextran-augmented and 7,12-dimethyl benz(a)anthracene-initiated skin carcinogenesis

Tannic acid (TA) is naturally occurring polyphenol present in fruits and vegetables. In this study we report that TA inhibits the carcinogenic effect of 7,12-dimethylbenz(a)anthracene (DMBA) in normal and iron-overloaded mice skin. Albino Swiss mice were given iron–dextran and pretreated with a single topical application of tannic acid; after 1 h, tumors were initiated by multiple topically application of DMBA. Appearance, number, and percent tumor incidence were recorded. When compared with the control group, the pretreated groups showed a significantly higher inhibition of tumor incidence. The induction of [3H]thymidine incorporation in cutaneous DNA and lipid peroxidation was inhibited in TA-pertreated animals as compared with the normal control group. Based on this study, we propose that TA significantly inhibits the augmentation potential of iron–dextran. A depletion in lipid peroxidation levels in TA-pretreated groups indicates that excessive generated oxidants in the mice skin tissues may be quenched by TA and because of the chelation of redox active iron and its faster elimination from the body. In conclusion, our data suggest that TA may be an effective chemopreventive agent and may offer protection against iron mediated skin cancer. J. Trace Elem. Exp. Med. 17:21–29, 2004. © 2004 Wiley-Liss, Inc.