Baicalein inhibits DMBA-DNA adduct formation by modulating CYP1A1 and CYP1B1 activities

Flavonoids are phenolic compounds isolated from plants, and several of them like genistein and quercetin, have been documented to be effective in preventing cancer. Baicalein, a flavonoid extracted from the root of Scutellaria species, is widely used as a health supplement and herbal medicine in Asian countries. In this study, the chemopreventive effect of baicalein on 7,12-dimethylbenz[a]anthracene (DMBA)-induced DNA damage was evaluated in an established cell culture model. In a preliminary screening, baicalein was identified to be a strong inhibitor to EROD activities induced by DMBA in MCF-7 cells. Subsequent enzyme kinetic analysis revealed that baicalein was a competitive inhibitor to EROD, and CYP1A1 and CYP1B1 gene expressions were also determined. Baicalein could reduce the CYP1A1/1B1 mRNA expressions induced by DMBA, and the mRNA abundance of CYP1A1 appeared to be more responsive than that of CYP1B1. A XRE-luciferase gene reporter assay indicated that AhR transactivation was suppressed. Since CYP1A1/1B1 were responsible for the biotransformation of polycyclic aromatic hydrocarbons, baicalein also demonstrated its ability to reduce DMBA-DNA adduct formation in MCF-7 cells. This study suggested that the natural occurring baicalein could be an agent preventing carcinogen-DNA adduct formation. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.