Structure of flavonoids influences the degree inhibition of Benzo(a)pyrene - induced DNA damage and micronuclei in HepG2 cells.

Flavonoids are plant derivatives of flavone of which chemical structure is characterized by various degrees of hydroxylation and glycosidic substitution. In the present study we investigated the protective effect of two structurally different groups of flavonoids against-benzo[a]pyrene (B(a)P)-induced genotoxic effects on human hepatocellular carcinoma (HepG2) cells. The first group of flavonoids: fisetin, kaempferol, galangin, quercetin, and luteolin, hydroxylated at the 3´,4´-position on the B ring, 3 - position of C ring and on the A ring was able to inhibit significantly B(a)P-induced genotoxic effects in a greater degree than the second group of flavonoids: chrysin, 7-hydroxyflavone, 7,8-dihydroxyflavone and baicalein (hydroxylated on the A ring) which showed a statistically significant inhibition of genotoxicity mainly at higher concentrations (10 and 25 µM). The tenth flavonoid tested rutin, which contains hydroxyl group at the position 3 of C ring, substituted by the sugar rutinose, was not able to inhibit effectively genotoxic changes induced by B(a)P. Our results, obtained with help of micronucleus test and single cell gel electrophoresis (comet assay) suggest that inhibition of B(a)P-induced DNA lesions and micronuclei correlates with the structural arrangement and organization of the hydroxyl groups in the molecular structure of the flavonoids tested.