TY - JOUR T1 - Regioselective Glucuronidation of Tanshinone IIa after Quinone Reduction: Identification of Human UDP-Glucuronosyltransferases, Species Differences, and Interaction Potential JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1132 LP - 1140 DO - 10.1124/dmd.109.031864 VL - 38 IS - 7 AU - Qiong Wang AU - Haiping Hao AU - Xuanxuan Zhu AU - Guo Yu AU - Li Lai AU - Yitong Liu AU - Yuxin Wang AU - Shan Jiang AU - Guangji Wang Y1 - 2010/07/01 UR - http://dmd.aspetjournals.org/content/38/7/1132.abstract N2 - We have previously identified that the predominant metabolic pathway for tanshinone IIa (TSA) in rat is the NAD(P)H:quinone oxidoreductase 1 (NQO1)-mediated quinone reduction and subsequent glucuronidation. The present study contributes to further research on its glucuronidation enzyme kinetics, the identification of human UDP-glucuronosyltransferase (UGT) isoforms, and the interaction potential with typical UGT substrates. A pair of regioisomers (M1 and M2) of reduced TSA glucuronides was found from human, rat, and mouse, whereas only M1 was found in dog liver S9 incubations. The overall glucuronidation clearance of TSA in human liver S9 was 11.8 ± 0.8 μl/min/mg protein, 0.7-, 0.8-, and 3-fold of that in the mouse, rat, and dog, respectively. Using intrinsic clearance M2/M1 as a regioselective index, opposite regioselectivity was found between human (0.7) and mouse (1.3), whereas no significant regioselectivity was found in rat. In a sequential metabolism system, by applying human liver cytosol as an NQO1 donor combined with a screening panel of 12 recombinant human UGTs, multiple UGTs were found involved in the M1 formation, whereas only UGT1A9 and, to a very minor extent, UGT1A1 and UGT1A3 contributed to the M2 formation. Further enzyme kinetics, correlation, and chemical inhibition studies confirmed that UGT1A9 played a major role in both M1 and M2 formation. In addition, TSA presented a potent inhibitory effect on the glucuronidation of typical UGT1A9 substrates propofol and mycophenolic acid, with an IC50 value of 8.4 ± 1.8 and 8.9 ± 1.9 μM, respectively. This study will help to guide future studies on characterizing the NQO1-mediated reduction and subsequent glucuronidation of other quinones. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics ER -