A sensitive LC-MS/MS method for simultaneous quantification of geniposide and its active metabolite genipin in rat...

Genipin (GP), an active metabolite of geniposide (GE), exhibits more potent pharmacological effects than its parent compound. In this paper, a sensitive LC-MS/MS method was developed and fully validated for the simultaneous determination of GE and GP in rat plasma. We found that GP degraded rapidly in rat plasma at room temperature as a result of irreversible binding with the endogenous nucleophiles in plasma. GP was stable when the sample's pH was ≤4.0. The degradation of GP in rat plasma was well prevented by immediate addition of 5% glacial acetic acid to the freshly collected plasma. The detection was performed on a tandem mass spectrometer coupled with electrospray ionization source in negative mode. Quantification was conducted by multiple reaction monitoring of the transitions [M + CH₃ COO]^- m/z 447.3 → 225.3 for GE and [M - H]^- m/z 225.2 → 123.1 for GP. The method exhibited high sensitivity (LLOQ 1 ng/mL for GE and 0.2 ng/mL for GP) by selecting the acetate adduct ions as the precursor ions for GE. The robust developed method was successfully applied to a pharmacokinetic study in rats after oral administration of GE.