UPLC-QTOF-MS/MS Based Screening and Identification of the Metabolites in Rat Bile After Oral Administration of Imperatorin

The detection of drug metabolites, particularly for minor metabolites, continues to be a challenge owing to the complexity of biological samples. Imperatorin is an active natural furocoumarin ingredient originating from many traditional Chinese herbal medicines. In the present study, the metabolites of imperatorin after oral administration were qualitatively investigated, and possible metabolic pathways of it were subsequently proposed. Bile samples were collected after oral administration and pretreated by the application of Waters Ostro. The QTOF-MS/MS data was acquired using ultra high performance liquid chromatography coupled to quadrupole time flight spectrometry (UPLC-QTOF-MS). Based on this analytical strategy, 32 metabolites (23 phase I and 9 phase II metabolites) were identified in rat bile. The results demonstrated that C5H8 could be easily eliminated from imperatorin forming the metabolite M1. It also indicated that imperatorin and M1 underwent extensive metabolic reactions including oxidation, hydrolysis, methylation, glucuronide conjugation, C2H5NO2S conjugation and C3H5NO2S conjugation. This is the first study of imperatorin metabolism in bile samples. The proposed metabolic pathways in this research will provide essential data for further pharmaceutical studies of other linear-type furocoumarins.