丹皮酚在人肝微粒体中主要经CYP1A2代谢

Paeonol, the primary active component of a traditional Chinese medicine Moutan Cortex, has a wide range of pharmacological activities. As compared to the extensive research of the pharmacological activities of paeonol, few studies have dealed with its metabolism and pharmacokinetics. Several Phase II metabolites and the only one Phase I metabolite of paeonol (the O-demethylated metabolite of paeonol, resacetophenone) has been detected in studies with rats. As one of the major metabolites, resacetophenone reached a maximum concentration approximately 20 min after dosing. However, no information is available to date about the Phase I metabolites and which isozyme of Phase I metabolic enzyme involved in this reaction in human. In present study, we elucidated the O-demethylation pathway of paeonol and identified one O-demethylated metabolite (resacetophenone) in HLMs by comparing the tandem mass spectra and the chromatographic retention time with that of the standard compound. A kinetic study showed that paeonol O-demethylation by HLMs followed Michaelis-Menten kinetics. The kinetics parameters values of HLMs for paeonol O-demethylation were Km = 24.1 ± 1.3 μM and Vmax = 577.7 ± 10.8 pmol/min/mg protein. Among recombinant CYP isozymes examined in the present study, only CYP1A2 and CYP2A6 isozymes exhibited paeonol O-demethylation activity. However, it is noteworthy that in 11 individual human liver microsomes, the activities of paeonol O-demethylation were significantly correlated with the activities toward phenacetin, a proposed CYP1A2-selective probe substrate, but not with the activities toward coumarin, a proposed CYP2A6-selective probe substrate. In addition, the extensive inhibition in HLMs obtained with furafylline (CYP1A2-selective inhibitor) provide further evidence of CYP1A2 involvement. In combination, we demonstrate that CYP1A2 and CYP2A6 are involved in the paeonol O-demethylation and that CYP1A2 plays a major role in paeonol O-demethylation in HLMs. Idenficiation of CYP1A2 as being responsible for paeonol O-demethylation will greatly improve future investigations of CYP1A2 interindividual differences associated with paeonol clinical trials and the magnitude of drug-drug interactions