[Aryl Hydrocarbon Receptor Ligand Activity of Extracts from 62 Herbal Medicines and Effect on Cytochrome P450...

Aryl hydrocarbon receptor (AhR) ligand activity of the extracts of 62 herbal medicines was examined using yeast reporter assay. Fifty-eight herbal extracts exhibited AhR ligand activity. The highest activity was observed with Ogon (Scutellariae Radix), followed by Oren (Coptidis Rhizoma), Kujin (Sophorae Radix) and Shoma (Cimicifiigae Rhizoma). When these extracts were treated with hesperinase, a hydrolase for sugar conjugates, the aglycones showed higher activity than the parent extracts. Among the constituents of Ogon extract, baicalein and wogonin showed AhR ligand activity, while the sugar conjugate of baicalein, baicalin, was inactive. Among the flavonoid components of these herbal medicines, flavone and chrysin exhibited high ligand activity for AhR. Ethoxyresorufin O-dealkylase (EROD) activity due to CYP1A1 in HepG2 cells was enhanced by the addition of baicalein. Baicalein also decreased the 3-methylcholanthrene-induced increase of EROD activity, but this effect was not statistically significant. When wogonin or baicalein was orally administered at the dose of 100 mg/kg to mice, EROD activity in liver was only slightly changed. Furthermore, when Ogon extract was co-administered with 3-methylcholanthrene, the EROD and methoxyresorufin O-dealkylase activities were not significantly changed. These results indicate that many herbal extracts have AhR ligand activity, and their inducing effect on CYP1A1/2 can be evaluated in HepG2 cells.