Rapid detection and structural characterization of verapamil metabolites in rats by UPLC-MS and UNIFI platform.

High-resolution mass spectrometry (HRMS) is an important technology for studying biotransformations of drugs in biological systems. In order to process complex HRMS data, bioinformatics, including data-mining techniques for identifying drug metabolites from liquid chromatography/high-resolution mass spectrometry (LC/HRMS) or multi-stage mass spectrometry (MS ) datasets as well as elucidating the detected metabolites' structure by spectral interpretation software, become important tools. Data-mining technologies have widely been used in drug metabolite identification, including mass defect filter, product ion filters, neutral-loss filters, control sample comparison, and extracted ion chromatographic analysis. However, the metabolites identified by current different technologies are not the same, indicating the importance of technique integration for efficient and complete identification of metabolic products. In this study, a universal, high-throughput workflow for identifying and verifying metabolites by applying the drug metabolite identification software UNIFI is reported, to study the biotransformation of verapamil in rats. A total of 71 verapamil metabolites were found in rat plasma, urine and faeces, including two metabolites that have not been reported in the literature. Phase I metabolites of verapamil were identified as N-demethylation, O-demethylation, N-dealkylation and oxidation and dehydrogenation metabolites; phase II metabolites were mainly glucuronidation and sulphate conjugates, indicating that UNIFI software could be effective and valuable in identifying drug metabolites.