Potent and selective inhibition of magnolol on catalytic activities of UGT1A7 and 1A9.

Liangliang Zhu, Guangbo Ge, Yong Liu, Guiyuan He, Sicheng Liang, Zhongze Fang, Peipei Dong, Yunfeng Cao, Ling Yang

Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.

Xenobiotica; the fate of foreign compounds in biological systems 2012 Oct

filter terms:

1. Human exposure to magnolol can reach a high dose in daily life. Our previous studies indicated that magnolol showed high affinities to several UDP-glucuronosyltransferases (UGTs) This study was designed to examine the in vitro inhibitory effects of magnolol on UGTs, and further to evaluate the possibility of the in vivo inhibition that might happen. 2. Assays with recombinant UGTs and human liver microsomes (HLM) indicated that magnolol (10 µM) can selectively inhibit activities of UGT1A9 and extra-hepatic UGT1A7. Inhibition of magnolol on UGT1A7 followed competitive inhibition mechanism, while the inhibition on UGT1A9 obeyed either competitive or mixed inhibition mechanism, depending on substrates. The K(i) values for UGT1A7 and 1A9 are all in nanomolar ranges, lower than possible magnolol concentrations in human gut lumen and blood, indicating the in vivo inhibition on these two enzymes would likely occur. 3. In conclusion, UGT1A7 and 1A9 can be strongly inhibited by magnolol, raising the alarm for safe application of magnolol and traditional Chinese medicines containing magnolol. Additionally, given that UGT1A7 is an extra-hepatic enzyme, magnolol can serve as a selective UGT1A9 inhibitor that will act as a new useful tool in future hepatic glucuronidation phenotyping.

Citation

Liangliang Zhu, Guangbo Ge, Yong Liu, Guiyuan He, Sicheng Liang, Zhongze Fang, Peipei Dong, Yunfeng Cao, Ling Yang. Potent and selective inhibition of magnolol on catalytic activities of UGT1A7 and 1A9. Xenobiotica; the fate of foreign compounds in biological systems. 2012 Oct;42(10):1001-8