Flavanols in nuclei and cytoplasm: reduction of the micronuclei-inducing effect of aflatoxin b1 in v79 cells through catechin

Nuclei of V79 cells showed that, in response to the carcinogen aflatoxin B 1 (0.10 - 2.5 μg/ml), the average number of micronuclei was significantly increased in comparison with controls. Pre-incubation of the cells in (+)-catechin at 0.01, 0.10 and 1.00 mg/L resulted in a significant reduction of micronuclei. With epigallocatechin gallate (0.001, 0.01 and 0.1 mg/L), a major flavanol in tea leaves, the reducing beneficial effect was not so pronounced. Using UV-VIS spectroscopic titration, this galloylated tea flavanol was found to associate more strongly with serum albumin than (+)-catechin; this may be one reason why epigallocatechin gallate showed a lower protective effect against the clastogenic properties of aflatoxin B 1 than (+)-catechin. The intracellular localization of flavanols was assayed histochemically with the selective DMACA reagent. Nuclei of V79 cells as well as nuclei from different types of human cells showed a particularly high affinity for added (+)-catechin and (-)-epicatechin. Polymorphonuclear lymphocytes were found to bind maximal amounts of catechins along the border lines of their segments. The inhibition of the formation of aflatoxin B 1 -induced micronuclei by catechins and the predominance of nuclear-associated catechins supports the assumption that the nucleus itself might be the preferred site of protective mechanisms.