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. Both two metabolites have not been reported in the literatures. The metabolic pathways of ecabet in rat were also proposed in this paper.