Identification of the metabolites of ecabet bismuth in rat bile by liquid chromatography-electrospray ionization-tandem mass spectrometry

In the present study, a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method was developed for the screening and the structural elucidation of the metabolites of ecabet bismuth in rat bile. Solid-phase extraction cartridges were used for sample pre-treatment and a gradient liquid chromatographic system composed of 10 mM ammonium acetate buffer and methanol was used for chromatographic separation on a Phenomenex Kromasil C-18 column. The triple quadrupole mass spectrometer was employed to thoroughly detect and acquire the detailed MS/MS spectra of ecabet and its metabolites. By comparing the chromatographic retention behaviors, as well as the changes in molecular weight and full-scan MS/MS spectra of the potential metabolites with those of the parent compound, two main metabolites were identified as glucuronide conjugate of carbonylated ecabet (7-oxo-ecabet) and glucuronide conjugate of ecabet. Neither of the two metabolites have previously been reported in the literature. The metabolic path ways of ecabet in rat were also proposed in this paper.