Metabolites of puerarin identified by liquid chromatography tandem mass spectrometry: Similar metabolic profiles in liver and intestine of rats

Puerarin is a major active ingredient of Pueraria Radix. Puerarin may exert its medicinal functions in part via its metabolites. In this study, we identified these metabolites to better understand and elucidate puerarin's metabolic pathway. Puerarin was intravenously administered to rats and then metabolites in plasma samples were identified by rapid resolution liquid chromatography electrospray ionization-collision induced dissociation tandem mass spectrometry (RRLC-ESI-CID–MS/MS). Chromatography was conducted on a Zorbax SB C18 column (2.1 × 100 mm, 1.8 μm) at 30 °C, with a gradient mobile phase consisting of 0.05% formic acid and acetonitrile, a flow rate of 0.2 mL min−1, and a total run time of 14 min. MS/MS acquisition parameters were as follows: positive ionization mode, dry gas: nitrogen, 10 L min−1, dry temperature: 350 °C, nebulizer: 40 psi, capillary: −3500 V, scan range: 250–800. The autoMS, manual, or multiple reaction monitoring mode was selected as required. Two glucuronidated metabolites of puerarin (M1 and M2) were detected. M1 and M2 are presumed to be puerarin-7-O-glucuronide and puerarin-4′-O-glucuronide, respectively, and M2 likely is suspected to be the major metabolite because it represented the predominate peak. Kinetic studies of metabolites demonstrated that M1 and M2 were detected in rat plasma at 5 min after intravenous administration of puerarin, the levels of M1 and M2 then reached their peaks at 10–15 and 15–30 min, respectively. The metabolic profiles were similar in rat liver and intestine investigated by in situ liver and intestine perfusion, indicating that no metabolic regioselectivity of puerarin occurs in the two organs.