title: In vitro identification of cytochrome P450 isoforms responsible for the metabolism of 1-hydroxyl-2,3,5-trimethoxy-xanthone purified from Halenia elliptica D. Don.
abstract: 1-Hydroxyl-2,3,5-trimethoxyxanthone (HM-1) is one of the main constituents extracted from Halenia elliptica D. Don, which is a traditionally used Tibetan medicinal plant. The aim of this study was to illustrate the proposed metabolic pathways of HM-1 and identify which cytochrome P450 (CYP450) isoforms involved in its metabolism by using pooled human liver microsomes (HLMs) and recombinant CYP450 isoforms with selective chemical inhibitors. Metabolites were identified by high performance liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LCMS(n)-ESI-IT-TOF) and nuclear magnetic resonance spectroscopy (hydrogen-1 NMR and carbon-13 NMR). Three metabolites (M1-M3) were identified, which demonstrated that demethylation and hydroxylation were the major Phase I metabolic reactions for HM-1 in HLMs. The structure of another metabolite (M4) was still unclear. The enzymatic kinetics of M1 (K(m)=23.19±14.20 μM) and M2 (Km=32.06±17.09 μM) exhibited substrate inhibition; whereas, the formation of M3 (K(m)=5.73±0.70 μM) and M4 (K(m)=16.43±5.12 μM) displayed Michaelis-Menten kinetics. The intrinsic clearance (V(max)/K(m)) of M3 was highest among these metabolites, suggesting that M3 was the major metabolite of HM-1. Moreover, CYP3A4 and CYP2C8 were the primary CYP450 isoform responsible for the metabolism of HM-1. CYP1A2, CYP2A6, CYP2B6, CYP2C9 and CYP2C19 were also involved in HM-1 metabolism, especially in the formation of M3. This study finally provides evidence of substrate inhibition and metabolism-based drug-drug interaction for the medicinal preparations containing HM-1 used in clinic.
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Ru
authors.initials: R
authors.lastname: Feng
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
authors.forename: Xuelin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Xiang-Shan
authors.initials: XS
authors.lastname: Tan
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
authors.forename: Penelope M Y
authors.initials: PM
authors.lastname: Or
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Jing-Yi
authors.initials: JY
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Min
authors.initials: M
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Chi-Yu
authors.initials: CY
authors.lastname: He
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China.
authors.forename: Jian-Gong
authors.initials: JG
authors.lastname: Shi
authors.affiliation: Department of Medicinal Chemistry & Pharmacognosy (MC 781), UIC College of Pharmacy, Chicago, IL 60612-7231, USA.
authors.forename: Chun-Tao
authors.initials: CT
authors.lastname: Che
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
authors.forename: John H K
authors.initials: JH
authors.lastname: Yeung
authors.affiliation: State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China. Electronic address: wangyan@imm.ac.cn.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000378:metabolism*; D029965:Gentianaceae / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008862:Microsomes, Liver / Q000201:enzymology*; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry* / Q000378:metabolism; D020033:Protein Isoforms; D018609:Tibet; D044004:Xanthones / Q000737:chemistry / Q000378:metabolism*
chemical_list: C478004:1-hydroxy-2,3,5-trimethoxyxanthone; D020033:Protein Isoforms; D044004:Xanthones; D003577:Cytochrome P-450 Enzyme System
keywords: Cytochrome P450; Halenia elliptica; Human liver microsomes; LCMS(n)-IT-TOF; Xanthone