Metabolism of 5-isopropyl-6-(5-methyl-1,3,4-oxadiazol-2-yl)-N-(2-methyl-1H-pyrrolo[2,3-b]pyridin-5-yl)pyrrolo[2,1-f][1,2,4]triazin-4-amine (BMS-645737): identification of an unusual N-acetylglucosamine conjugate in the cynomolgus monkey

Combined Experimental and Computational Study on the Transformation of a Novel 1,3,4-Oxadiazole Thioether Nematicide in Aqueous Solutions

It has been demonstrated that Exianliuyimi (EXLYM) exhibits good nematocidal activity. As a potential nematicide, EXLYM and its transformation products (TPs) may generate emerging pollutants with hazardous effects on the ecosystem. In this study, the fate of EXLYM in aqueous solutions was investigated using experimental and theoretical approaches. Laboratory-scale experiments showed that EXLYM is hydrolytically stable. Microbial processes are primarily responsible for the oxidation of sulfur in aqueous solutions. Under simulated sunlight, the t_1/2 values of EXLYM in acidic, neutral, and alkaline buffer solutions were 5.02, 3.83, and 5.55 h, respectively. Six TPs were identified using a non-target screening strategy realized by ultra-high-performance liquid chromatography coupled with Q-Exactive Orbitrap high-resolution mass spectrometry and ¹⁸O-labeling experiments. Four of these were unambiguously confirmed using authentic standards. Reactive oxygen species scavenging experiments, ¹⁸O-labeling experiments, and quantum-theoretical calculations suggested that EXLYM could degrade mainly through four pathways: sulfur oxidation, nucleophilic aromatic photosubstitution, C-S bond cleavage, and oxidative ring-opening. The proposed degradation kinetics, TPs, and transformation pathways in aqueous solutions provide valuable information on the fate of EXLYM in aquatic ecosystems and lay the foundation for further toxicological tests.

Novel cytochrome P450-mediated ring opening of the 1,3,4-oxadiazole in setileuton, a 5-lipoxygenase inhibitor

Setileuton [4-(4-fluorophenyl)-7-[({5-[(1S)-1-hydroxy-1-(trifluoromethyl)propyl]-1,3,4-oxadiazol-2-yl}amino)methyl]-2H-1-benzopyran-2-one] is a selective inhibitor of the 5-lipoxygenase enzyme, which is under investigation for the treatment of asthma and atherosclerosis. During the development of setileuton, a metabolite (M5) was identified in incubations with rat, dog, and human liver microsomes that represented the addition of 18 Da to the 1,3,4-oxadiazole portion of the molecule. Based on mass spectral data, a ring opened structure was proposed and confirmed through comparison with a synthetic standard. The metabolic ring opening was examined in vitro in rat liver microsomes and was determined to be mediated by cytochrome P450s (P450s). Upon examination of the specific P450s involved using cDNA-expressed rat P450s, it was shown that CYP1A2 likely was the major isoform contributing to the formation of M5. Studies using stable labeled molecular oxygen and water demonstrated that the oxygen was incorporated from molecular oxygen, rather than water, and confirmed that the metabolic formation was oxidative. An alternative, comparatively slow pathway of chemical hydrolysis also was identified and described. Three potential mechanisms for the two-step metabolic ring opening of the 1,3,4-oxadizole are proposed.

Correlative analysis of metabolite profiling of Danggui Buxue Tang in rat biological fluids by rapid resolution LC-TOF/MS

In this work, the metabolite profiles of Danggui Buxue Tang (DBT) in rat bile and plasma were qualitatively described, and the possible metabolic pathways of DBT were subsequently proposed. Emphasis was put on correlative analysis of metabolite profiling in different biological fluids. After oral administration of DBT, bile and plasma samples were collected and pretreated by solid phase extraction. Rapid resolution liquid chromatography coupled to time-of-flight mass spectrometry (RRLC-TOFMS) was used for characterization of DBT-related compounds (parent compounds and metabolites) in biological matrices. A total of 142 metabolites were detected and tentatively identified from the drug-containing bile and plasma samples. Metabolite profiling shows that rat bile contained relatively more glutathione-derived conjugates, more saponins compounds and more diverse forms of metabolites than urine. The metabolite profile in plasma revealed that glucuronide conjugates of isoflavonoids, dimmers, acetylcysteine conjugates and parent form of phthalides, as well as saponin aglycones were the major circulating forms of DBT. Collectively, the metabolite profile analysis of DBT in different biological matrices provided a comprehensive understanding of the in vivo metabolic fates of constituents in DBT.