Pharmacokinetics of irisolidone and its main metabolites in rat plasma determined by ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry

Irisolidone, a major isoflavone found in Pueraria lobata flowers, exhibits a wide spectrum of bioactivities, while its metabolic pathways and the pharmacokinetics of its metabolites in vivo have not been investigated yet. In the present study, an ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF MS) method was employed to investigate the metabolic pathways of irisolidone and the pharmacokinetics of its main metabolites in rats, after a single 100 mg/kg oral dose of irisolidone. Protein precipitation method was used to prepare plasma samples. A total of 15 metabolites included irisolidone were detected and tentatively identified based on the mass spectral fragmentation patterns, elution order or confirmed using available reference standards. The pharmacokinetics of the main metabolites included three glucuronide metabolites tectorigenin-7-O-glucuronide (Te-7G), 6-hydroxybiochanin A-6-O-glucuronide (6-OH-BiA-6G), irisolidone-7-O-glucuronide (Ir-7G), and three sulfate metabolite tectorigenin-7-O-sulfate-4′-O-sulfate (Te-7S-4′S), tectorigenin-7-O-sulfate (Te-7S) and irisolidone-7-O-sulfate (Ir-7S), and aglycone tectorigenin (Te), and irisolidone (Ir) were evaluated. The plasma concentrations reached maximal values of 0.297 μmol/L at 10.3 h for Te-7S-4′S, 0.199 μmol/L at 21.7 h for Te-7G, 0.154 μmol/L at 8.00 h for Te-7S, 4.10 μmol/L at 15.3 h for 6-OH-BiA-6G, 10.7 μmol/L at 9.71 h for Ir-7G, 0.918 μmol/L at 11.3 h for Te, 0.150 μmol/L at 8.67 h for Ir-7S, and 0.843 μmol/L at 9.67 h for Ir, respectively. Since the total plasma concentrations of conjugated metabolites were much higher than that of the irisolidone aglycone, an extensive phase II metabolism plays an important role in the pharmacokinetics of irisolidone in vivo.