Inhibitory effect of tannic acid from nutgall on iron-dextran augmented 7,12-dimethyl benz(a)anthracene-initiated and croton oil-promoted skin carcinogenesis

Abstract

Tannic acid (TA) is naturally occurring polyphenols present in fruits and vegetables. In this study, inhibition of the carcinogenic potential of croton oil in normal and iron overloaded mice skin by TA is reported. Albino Swiss mice were given iron-dextran for two weeks and were pretreated with a single topical application of tannic acid. After one hour tumors were initiated by a single dose of 7,12-dimethylbenz(a)anthracene (DMBA) the promoting agent croton oil was applied twice a week for 30 weeks. The appearance, number and percent tumor incidences were recorded. When compared to control groups, the pretreated groups showed a significant high inhibition of tumors incidences. Biochemical studies in mice skin tissues were based on the measurement of lipid peroxidation (LPO). TA diminished cutaneous LPO level in mice skin as compared to the untreated groups. This study showed that TA inhibits the augmentation potentials of croton oil and iron dextran significantly. A depletion in LPO levels in TA pretreated groups indicates that excessive generated oxidants in the mice skin tissues may be quenched by TA because of chelation of redox active iron and its faster elimination from the body. It is supposed that inhibition of iron mediated oxidative stress by TA may be responsible for diminishment of cutaneous tumorigenesis.