Comparative evaluation of the chemopreventive efficacy of green and black tea polyphenols in the hamster buccal pouch carcinogenesis model.

OBJECTIVES

To evaluate the comparative chemopreventive efficacy of green tea polyphenols (Polyphenon-E) and black tea polyphenols (Polyphenon-B) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis.

DESIGN AND METHODS

Hamsters were divided into 6 groups. Animals in group 1 served as controls. Animals in groups 2 and 3 were administered 0.05% Polyphenon-E and B, respectively, in the diet. The right buccal pouches of animals in groups 4-6 were painted with 0.5% DMBA three times a week for 14 weeks. While group 4 received no further treatment, hamsters in groups 5 and 6 received diet containing 0.05% Polyphenon-E and B, respectively. The status of carcinogen-metabolising enzymes, lipid peroxidation and glutathione-dependent antioxidants in the buccal pouch and liver, as well as the frequency of bone marrow micronuclei were used as biomarkers.

RESULTS

Application of DMBA induced HBP carcinomas, increased genotoxicity with an imbalance in carcinogen-metabolising enzymes and the cellular redox status. Inhibition of HBP carcinomas by Polyphenon-E and B was associated with a significant decrease in phase I enzymes, modulation of lipid peroxidation and enhanced antioxidant and phase II enzyme activities.

CONCLUSION

The greater efficacy of Polyphenon-B in inhibiting HBP carcinogenesis suggests that it may have a major impact in the chemoprevention of oral cancer.