PT  - JOURNAL ARTICLE
AU  - Yu, Lushan
AU  - Pu, Jianbin
AU  - Zuo, Minjuan
AU  - Zhang, Xia
AU  - Cao, Yang
AU  - Chen, Shifeng
AU  - Lou, Yan
AU  - Zhou, Quan
AU  - Hu, Haihong
AU  - Jiang, Huidi
AU  - Chen, Jianzhong
AU  - Zeng, Su
TI  - Hepatic Glucuronidation of Isoneochamaejasmin A from the Traditional Chinese Medicine <em>Stellera Chamaejasme</em> L. Root
AID  - 10.1124/dmd.113.055962
DP  - 2014 Apr 01
TA  - Drug Metabolism and Disposition
PG  - 735--743
VI  - 42
IP  - 4
4099  - http://dmd.aspetjournals.org/content/42/4/735.short
4100  - http://dmd.aspetjournals.org/content/42/4/735.full
SO  - Drug Metab Dispos2014 Apr 01; 42
AB  - Isoneochamaejasmin A (INCA), a biflavonoid, is one of main active ingredients in the dried root of Stellera chamaejasme L., a widely used traditional Chinese medicine. In the present study, we identified the glucuronidation metabolite of INCA and characterized the UDP glucuronosyltransferases (UGTs) responsible for INCA glucuronidation. 7-O-glucuronide (M1) and 4′-O-glucuronide (M2) were identified by incubation of INCA with human liver microsomes (HLMs) in the presence of UDP glucuronic acid, and their structures were confirmed by high-resolution mass spectrometry and nuclear magnetic resonance analyses. Although INCA is a single enantiomer molecule, its M1 metabolite showed two equal-size peaks on a πNAP stationary phase but only one peak on a C18 stationary phase, indicating that the 7-/7′′- and 4′-/4′′′-hydroxyl groups of INCA were in different spatial configurations relative to each other. Among the recombinant human UGT isoform test and correlation analysis, UGT1A1, UGT1A3, and UGT1A9 were found to mediate M1 formation, whereas only UGT1A3 mediated M2 formation. Kinetic studies showed obvious species differences between human, mouse, rat, dog, and pig liver microsomes. UGT1A1, HLMs, and human intestinal microsomes, but not human kidney microsomes, exhibited substrate inhibition for the formation of M1. UGT1A1-mediated formation of M1 showed a 6- and 11-fold higher Vmax than did UGT1A3- and UGT1A9-mediated formation of M1, respectively. The results of the relative activity factor assay showed that UGT1A1 contributed approximately 75% in the formation of M1. These findings collectively indicate that UGT1A1 is the major enzyme in the formation of M1, whereas UGT1A3 is the major enzyme in the formation of M2.