Comparison of the Inhibition Capability of Baicalin and Baicalein towards Intestinal UDP-Glucuronosyltransferase (UGT) 1A10

Baicalin, the important flavonoid component isolated from Scutellariae radix, has been demonstrated to exhibit multiple pharmacological activities, and its anti-tumor activity has been drawing more and more attention in recent years: Baicalin can be metabolized into baicalein in intestine. The present study aims to compare the inhibition capability of baicalin and baicalein towards the specific intestinal drug metabolizing enzyme UDP-glucuronosyltransferase (UGT) 1A10. Baicalein showed stronger inhibition than baicalin towards UGT1A10, with the residual activity to be 46.5 and 5.5% of control activity for 100 mu M of baicalin and baicalein, respectively. Noncompetitive inhibition was demonstrated for the inhibition of baicalein towards UGT1A10, and the inhibition kinetic parameter (K-i) was calculated to be 8.1 mu M. All these results showed the stronger inhibition capability of baicalin than baicalein towards intestinal UDP-glucuronosyltransferase (UGT) 1A10.