title: [Inhibition of 1,3,8-trihydroxy-5-methoxyxanthone on cytochrome P450s].
abstract: OBJECTIVE
  To explore the inhibitive effects of 1,3,8-trihydroxy-5-methoxyxanthone (TMX) on cytochrome P450s (CYP450s) in human liver microsomes.
  
  
  METHODS
  Probe drugs were incubated with and without adding TMX to determine the changes of enzyme activities. The concentration ratio of metabolites to probe drugs was used to present enzyme activities. Concentrations of the probe drugs and their metabolites in the incubated mixture were detected by high performance liquid chromatography.
  
  
  RESULTS
  The variations (mean, 95%CI) of the activities of CYP1A2, CYP2C9, CYP2C19, CYP2E1 and CYP3A4 were 2.95 x 10(-3) (2.03 x 10(-3), 3.88 x 10(-3)), 3.14 x 10(-2) (1.87 x 10(-2), 4.42 x 10(-2)), 2.27 x 10(-3) (-1.4 x 10(-2),1.81 x 10(-2)), 7.72 x 10(-2) (-0.83 x 10(-2), 0.2374), and -0.2548 (-2.9802, 2.4707), respectively. The activities of CYP1A2 and CYP2C9 were significantly reduced in the present of TMX.
  
  
  CONCLUSIONS
  TMX (10 micromol/L) has significant inhibitive effect on the activities of CYP1A2 and CYP2C9, but no significant inhibitive effect on the activities of CYP2C19, CYP2E1 and CYP3A4.
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha 410013, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Cao
authors.forename: Ya-jie
authors.initials: YJ
authors.lastname: Cao
authors.forename: Zhe-yi
authors.initials: ZY
authors.lastname: Hu
authors.forename: Qi
authors.initials: Q
authors.lastname: Yu
authors.forename: Li-qing
authors.initials: LQ
authors.lastname: Wang
authors.forename: Gui-shan
authors.initials: GS
authors.lastname: Tan
authors.forename: Ze-neng
authors.initials: ZN
authors.lastname: Cheng
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006801:Humans; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D044004:Xanthones / Q000494:pharmacology*
chemical_list: C582242:1,3,8-trihydroxy-5-methoxyxanthone; D044004:Xanthones; D003577:Cytochrome P-450 Enzyme System