1. A comprehensive method for the simultaneous characterization of xenobiotic compound inhibition of nine major CYP enzymes in human liver microsomes was established by using 16 CYP-catalyzed reactions of 14 probe substrates with three cocktail incubation sets and a single LC/MS/MS analysis. 2. The three cocktail subgroups were developed to minimize the effects of organic solvents, polyunsaturated fatty acids and mutual substrate interactions: Group I was composed of tolbutamide (CYP2C9), S-mephenytoin (CYP2C19), testosterone (CYP3A4), dextromethorphan (CYP2D6); Group II was composed of nifedipine (CYP3A4), midazolam (CYP3A4), coumarin (CYP2A6), bupropion (CYP2B6), diclofenac (CYP2C9); Group III was composed of phenacetin (CYP1A2), chlorzoxazone (CYP2E1), omeprazole (CYP2C19 and CYP3A4), paclitaxel (CYP2C8), (+)-bufuralol (CYP2D6). In the case of CYP2C9, CYP2C19, CYP2D6 and CYP3A4, multiple probe substrates were used due to the phenomenon of multiple substrate-binding pockets and substrate-dependent inhibition. All probe metabolites were simultaneously analyzed with a polarity switching mode in a single LC/MS/MS run. 3. This method was validated against the single probe substrate assay using 12 well-characterized CYP inhibitors and two new entities (GT0918, MDV3100). The IC50 values of each inhibitor in the cocktail agreed well with that of the individual probe drug as well as with values reported in previous literatures.
Isochlorogenic acid A is widely present in fruits, vegetables and herbal medicines, and is characterized by anti-inflammatory, hepatoprotective and antiviral properties. However, little is known about its metabolic fate and pharmacokinetic properties. This study is thus designed to investigate the metabolic fate of isochlorogenic acid A. An analytical method based on high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC/Q-TOF MS) was established to characterize the metabolites of isochlorogenic acid A in the plasma, urine and feces of rats. A total of 32 metabolites were identified. The metabolic pathways mainly include hydrolyzation, dehydroxylation, hydrogenation and conjugation with methyl, glucuronic acid, glycine, sulfate, glutathione and cysteine. Moreover, the pharmacokinetic profiles of all the circulating metabolites were investigated. M11 resulting from hydrolyzation, dehydroxylation and hydrogenation was the dominant circulating metabolite after the intragastric administration of isochlorogenic acid A. The results obtained will be useful for further study of elucidating potential bioactive metabolites which can provide better explanation of the pharmacological and/or toxicological effects of this compound.
Guizhi Fuling capsule (GZFL), a traditional Chinese medicine formulation, is widely used in China to relieve pain from dysmenorrhea and is now in a Phase II clinical trial in the USA. Due to the low exposure of the five main medicative ingredients (amygdalin, cinnamic acid, gallic acid, paeoniflorin and paeonol) of GZFL in human, a strategy was built to qualitatively and quantitatively identify the possible metabolites of GZFL and to describe the pharmacokinetic profiles of GZFL in human. In this strategy, LC-Q-TOF/MS was used to identify and structurally elucidate the possible metabolites of GZFL in vivo; and a time-based metabolite-confirming step (TBMCs) was used to confirm uncertain metabolites. The simultaneously quantitation results by LC-MS/MS showed low exposure of the five medicative ingredients. According to the strategy we built, a total of 36 metabolites were found and structurally elucidated. The simultaneously semi-quantitative analysis by LC-MS/MS showed that obvious time-concentration curves could be established for 12 of the metabolites, and most of them showed a relatively higher exposure. This study provides a better understanding of the metabolic processes of GZFL in human.
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