Simultaneous determination of tectorigenin and its metabolites in rat plasma by ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry.

Tectorigenin is a major isoflavone found in the flowers of Pueraria thomsonii Benth. and the rhizomes of Belamcanda chinensis (L.) DC. It possesses hepatoprotective, estrogenic, hypoglycemic and anti-inflammatory activities. In the present study, the plasma pharmacokinetic profile of tectorigenin in rats was evaluated. We developed a selective and accurate U-HPLC/Q-TOFMS method for the simultaneous characterization of nine tectorigenin metabolites, and quantitation of six major metabolites in rat plasma, including tectorigenin-7-O-glucuronide-4'-O-sulfate (Te-7G-4'S), tectorigenin-di-O-sulfate (Te-diS), tectorigenin-7-O-glucuronide (Te-7G), tectorigenin-4'-O-glucuronide (Te-4'G), tectorigenin-7-O-sulfate (Te-7S) and tectorigenin after oral administration of tectorigenin (130mg/kg). The plasma concentrations reached maximal values of 6.20±2.05μmol/L at 0.96±0.68h for Te-7G-4'S, 4.42±1.36μmol/L at 1.92±2.15h for Te-diS, 33.50±4.89μmol/L at 0.75±0.67h for Te-7G, 3.28±1.01μmol/L at 0.75±0.67h for Te-4'G, 12.80±2.80μmol/L at 0.85±1.54h for Te-7S, and 12.0±0.63μmol/L at 0.23±0.15h for tectorigenin, respectively. Enterohepatic recirculation resulted in double or triple peaks concentration curve/time profiles of the metabolites. Since the total plasma concentrations of tectorigenin conjugated metabolites were much higher than that of the tectorigenin aglycone, an extensive phase II metabolism plays an important role in the pharmacokinetics of tectorigenin in vivo.