Effect And Inhibitory Type Of Magnolol And Honokiol On The Activities Of CYP450Isozymes Of Rats In Vitro

Cytochrome P450(CYP450) is the major metabolic enzymes of animals in vivo, which plays an important role in the biotransformation of endogenous compounds. Through the effect of drugs on the metabolism of substrates of the CYP450subtypes, we can predict the potential impact of drugs on the metabolism of other drugs. CYP450enzymes are inhibited or induced is the main cause of drug-drug interaction (DDI), Therefore, the DDI about combination therapy was particular importance to ensure clinical safety medication.Officinal Magnolia Bark is a common traditional Chinese medicine which has a long history of clinical application. Magnolol and honokiol are the main active constitutent of cortex magnoliae which are isomers. The pharmacological effects and clinical applications of magnolol and honokiol are very extensive. The absorption, metabolism and excretion of magnolol of rats in vivo, as well as the metabolism and distribution of honokiol in rat and human livers in vitro have been reported. The effect of magnolol and honokiol on liver microsomal CYP450isozymes in rats has not been reported. The effect of magnolol and honokiol on CYP450isozyme activity in vitro could not only predict its impact on drug metabolism in vivo, but also provide an important basis for clinical reasonable combination therapy of Chinese and Western medicine.In this paper, rat liver microsomes (RLM) were used to investigate the effect and inhibitory type of magnolol and honokiol on the activities of four major CYP450isozymes (CYP1A2, CYP2E1, CYP2C and CYP3A) of rats in vitro. Different concentration of ethoxyresorufin (the probe drug of CYP1A2),4-nitrophenol (the probe drug of CYP2E1), testosterone (the probe drug of CYP3A), tolbutamide (the probe drug of CYP2C) were incubated with or without magnolol and honokiol in rat microsomes respectively. The metabolite of the probe drugs were determined acording to fluorescence (resorufin), absorbance (4-nitrocatechol) by Multifunction Microplate Reader or HPLC (6(3-hydroxytestosterone and4-hydroxytolbutamide) respectively. The cytochrome P450activities were reflected by relative metabolic clearance rate (MCR).The results showed that:(1) magnolol had significant inhibitory effects on the activities of CYP1A2, and the value of IC50was10.0μmol.L-1, honokiol had significant inhibitory effects on the activities of CYP1A2and CYP2E1, the values of IC50were12.1and12.6μmol.L-1respectively. The inhibitory effect of magnolol and honokiol on liver microsomal CYP450isozymes were all in a dose-dependent fashion in rat liver microsomes.(2) The inhibitory kinetics of CYP1A2and CYP2E1investigated, and the inhibitory type of magnolol and honokiol to CYP1A2was competitive, the Ki value were10.0and6.2μmol·L-1respectively, honokiol to CYP2E1shown to be a non-competitive model with a Ki value of11.1μmol·L-1.