Identification of metabolites of geniposide in rat urine using ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

Geniposide, an iridoid glycoside, is an important and characteristic compound in the fruits of Gardenia jasminoides Ellis, a commonly used medicinal herb in Chinese traditional and folk medicine for the treatment of inflammation and jaundice. However, few studies have been carried out on the metabolism of geniposide. In this study, we have established a rapid and sensitive method using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOF-MS) for analysis of the metabolic profile of geniposide in rat urine after oral administration. A total of ten metabolites were detected and identified by comparing their fragmentation patterns with that of geniposide using Metabolynx™ and MassFragment™ software tools. The results revealed that the principal metabolism pathways of geniposide in rat occurred after deglycosylation of the irdoid glycoside take place and this is followed by glucuronidation and the pyran-ring cleavages. The major metabolite, the glucuronic acid conjugate of genipin as observed in vivo, was further confirmed by the in vitro enzymatic study. The results of this work have demonstrated the feasibility of the UPLC/ESI-QTOF-MS approach for rapid and reliable characterization of metabolites from iridoid compounds.