title: Deoxyschizandrin, a naturally occurring lignan, is a specific probe substrate of human cytochrome P450 3A.
abstract: To accurately predict the modifications done during metabolic processes by cytochrome P450 (P450) 3A enzyme, selecting substrates that best represent a broad range of substrate substitutions and that follow the Michaelis-Menten kinetic properties is highly necessary. In the present study, the oxidative pathways of deoxyschizandrin (DS), the most abundant lignan in Fructus Schisandrae fruit extract, were characterized with liver microsomes from human (HLM) and rat (RLM). Only one monohydroxylated metabolite 7(S)-hydroxylated metabolite (isoschizandrin, ISZ), was identified using liquid chromatography-mass spectrometry and nuclear magnetic resonance techniques. CYP3A4 and CYP3A5 were found to be the major isoforms involved in the monohydroxylation of DS. Also, the kinetic studies showed that DS hydroxylation obeyed Michaelis-Menten kinetics both in HLM and in RLM. However, the subsequent metabolism of ISZ was nearly nonexistent when DS was present. More importantly, the interactions between DS and three well characterized CYP3A probe substrates, testosterone (TST), midazolam (MDZ), and nifedipine (NIF), were studied. TST and MDZ were shown to compete with DS for the mutual binding site, causing Km to be increased. The presence of DS also lowered the binding affinities for MDZ and TST. However, DS showed only slight inhibitory effects on nifedipine (NIF) oxidation even though NIF was able to inhibit DS hydroxylation in a noncompetitive fashion. These results show that DS is a good representative substrate of MDZ and TST primarily due to their shared, large binding regions on CYP3A. Therefore, DS is an attractive candidate as a novel CYP3A probe substrate for predicting the metabolic modifications in CYP3A activity.
authors.affiliation: Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China (J.W., Y.C., Y.Z., Y.L., L.Z., G.G., L.Y.); Department of Biopharmaceutical Sciences, University of Illinois, Chicago, Illinois (J.Y.H.); Graduate University of Chinese Academy of Sciences, Beijing, China (J.W., L.Z.); Shanghai Institute of Planned Parenthood Research, Shanghai, China (Y.C.).
authors.forename: Jingjing
authors.initials: J
authors.lastname: Wu
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Cao
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: James Y
authors.initials: JY
authors.lastname: Hong
authors.forename: Liangliang
authors.initials: L
authors.lastname: Zhu
authors.forename: Guangbo
authors.initials: G
authors.lastname: Ge
authors.forename: Ling
authors.initials: L
authors.lastname: Yang
mesh_terms: D000818:Animals; D001711:Biotransformation / Q000502:physiology; D034242:Cyclooctanes / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System; D006801:Humans; D006900:Hydroxylation / Q000502:physiology; D007700:Kinetics; D017705:Lignans / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D008874:Midazolam / Q000378:metabolism; D009543:Nifedipine / Q000378:metabolism; D010084:Oxidation-Reduction; D011083:Polycyclic Compounds / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000378:metabolism
chemical_list: D034242:Cyclooctanes; D017705:Lignans; D011083:Polycyclic Compounds; C482833:isoschizandrin; D013739:Testosterone; C034734:schizandrin A; D003577:Cytochrome P-450 Enzyme System; D051544:Cytochrome P-450 CYP3A; D009543:Nifedipine; D008874:Midazolam