title: UDP-Glucuronosyltransferases 1A6 and 1A9 are the Major Isozymes Responsible for the 7-O-Glucuronidation of Esculetin and 4-Methylesculetin in Human Liver Microsomes.
abstract: Esculetin (6,7-dihydroxycoumarin, ET) and 4-methylesculetin (6,7-dihydroxy-4-methylcoumarin, 4-ME) are typical coumarin derivatives that are attracting considerable attention because of their wide spectrum of biologic activities, but their metabolism remains unknown. This study aimed to elucidate the in vitro UDP-glucuronosyltransferase (UGT) metabolism characteristics of ET and 4-ME. 7-O-monoglucuronide esculetin (ET-G) and 7-O-monoglucuronide 4-methylesculetin (4-ME-G) were identified by liquid chromatography-mass spectrometry (LC-MS) and (1)H-nuclear magnetic resonance ((1)HNMR) when ET or 4-ME was incubated with human liver (HLM) in the presence of UDP-glucuronic acid. Screening assays with 12 human expressed UGTs demonstrated that the formations of ET-G and 4-ME-G were almost exclusively catalyzed by UGT1A6 and UGT1A9. Phenylbutazone and carvacrol (UGT1A6 and UGT1A9 chemical inhibitors, respectively) at different concentrations (50, 100, and 200 μM) significantly inhibited the formation of glucuronidates of ET and 4-ME in HLM, UGT1A6, and UGT1A9 when the concentrations of ET and 4-ME ranged from 10 to 300 μM (P < 0.05). Clearance rates of ET in HLM, HIM, UGT1A6, and UGT1A9 were 0.54, 0.16, 0.69, and 0.14 ml/min/mg, respectively. Corresponding clearance rates values of 4-ME were 0.59, 0.03, 0.14, and 0.04 ml/min/mg, respectively. In conclusion, 7-O-monoglucuronidation by UGT1A6 and UGT1A9 was the predominant UGT metabolic pathway for both ET and 4-ME in vitro. The liver is probably the major contributor to the glucuronidation metabolism of ET and 4-ME. ET showed more rapid metabolism than 4-ME in glucuronidation.
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Lijun
authors: L
authors: Zhu
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Linlin
authors: L
authors: Lu
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Shan
authors: S
authors: Zeng
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Feifei
authors: F
authors: Luo
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Peimin
authors: P
authors: Dai
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Peng
authors: P
authors: Wu
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Ying
authors: Y
authors: Wang
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Liang
authors: L
authors: Liu
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.).
authors: Ming
authors: M
authors: Hu
authors: International Institute for Translational Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, PR China (Z.L.J., L.L.L., Z.S., L.F.F., D.P.M., W.P., W.Y., H.M., L.Z.Q.); Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas (H.M.); Department of Pharmaceutics, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, Guangdong, PR China (D.P.M., W.Y.); and State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau (SAR), PR China (L.L.) liuzq@gzucm.edu.cn.
authors: Zhongqiu
authors: Z
authors: Liu
mesh_terms: D000465:Algorithms; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020719:Glucuronides / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D011284:Pregnenolone / Q000031:analogs & derivatives* / Q000378:metabolism; D000090264:UDP-Glucuronosyltransferase 1A9; D014468:Umbelliferones / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D020719:Glucuronides; D006027:Glycosides; D007527:Isoenzymes; C000715591:UGT1A9 protein, human; D014468:Umbelliferones; C081583:esculentin steroid; C570020:4-methylesculetin; D011284:Pregnenolone; C110655:UDP-glucuronosyltransferase, UGT1A6; D014453:Glucuronosyltransferase; D000090264:UDP-Glucuronosyltransferase 1A9