Metabolic Profiles of Thioquinapiperifil Using Liquid Chromatography Quadrupole Time of Flight Mass Spectrometry

To date, many analogies of sildenafil, tadarafil, and vadenafil, which are phosphodiesterase-5 (PDE5) inhibitor have been reported. On the other hand, a novel type of PDE5 inhibitor, thioquinapiperifil has not yet been evaluated. Therefore, in this study, liquid chromatography quadrupole time of flight mass spectrometry (LC-Q-TOF-MS) was conducted to determine the in vitro and in vivo metabolites of thioquinapiperifil. Metabolites in urine and feces samples of rats injected with thioquinapiperifil and in human liver microsomal extract were characterized to examine its possible metabolic pathways. Metabolized samples were extracted and precipitated using acetonitrile and subsequently injected into the LC-Q-TOF-MS system. Peaks of interest were analyzed via tandem-mass spectrometry to identify the metabolite structure. A total of 11, 5, and 7 metabolites were detected in human liver microsomal extract, rat urine, and rat feces, respectively. The mass error values of all TOF mass results were within 5 ppm, indicating high accuracy. These newly identified metabolites may be useful for evaluating the toxicology of thioquinapiperifil and this knowledge may be applied to related forensic cases.