Glucuronide-sulfate Diconjugate as a Novel Metabolite of Glycyrrhetic Acid in Rat Bile

To study the metabolites of glycyrrhetic acid (GA) in rat bile, an analytical method was developed to identify GA and its metabolites by liquid chromatography mass spectrometry (LC-MS). Rat bile was collected after i.v. injection of GA. Three major GA-related peaks were detectable in rat bile by high-performance liquid chromatography (HPLC) analysis at 254 nm. LC-MS spectra showed their protonated molecular ions at m/z 727, 647, and 551. Furthermore, the three metabolites were also confirmed to exist in rat bile on LC-MS total ion chromatogram (TIC). Taken together with the susceptible nature to beta-glucuronidase digestion and alkaline conditions, they were identified to be a novel sulfate-glucuronide diconjugate and the known monoglucuronide and sulfate conjugate, respectively.