Pharmacokinetic comparisons of puerarin, daidzin and the glucuronide metabolite of puerarin after administration of total flavonoid from Gegen alone and total flavonoid from Gegen combined with total saponin from Sanqi in rats under different physiologica

• Simultaneous determination of puerarin glucuronide, puerarin and daidzin in rat plasma.
• An UPLC–MS/MS method was developed and applied for pharmacokinetic study.
• Comparative pharmacokinetics was performed in rats under different physiological states.
• Blood stasis syndrome had effect on pharmacokinetics of puerarin glucuronide, puerarin and daidzin.
• Pharmacokinetics of the three constituents changed when Gegen was used in combination with Sanqi.

Gegen is one of the most commonly used traditional Chinese medicines for promoting blood circulation and removing blood stasis. Puerarin and daidzin are the main active constituents of Gegen. Puerarin is mainly metabolized in rats by glucuronidation and the major metabolite from rat urine has been identified as puerarin-7-O-glucuronide through semi-preparative HPLC isolation and then spectroscopic analysis. The study investigated the pharmacokinetic behavior of puerarin-7-O-glucuronide (without enzymatic hydrolysis), puerarin and daidzin when total flavonoid from Gegen was administered in normal and blood stasis animals or in blood stasis animals alone or in combination with Sanqi. The plasma samples were processed by protein precipitation with methanol, and chromatographed on a Thermo Syncronis C18 column (10 cm × 2.1 mm, 1.7 μm) by gradient elution at a flow rate of 0.25 mL/min, and detected with a triple quadrupole tandem mass spectrometer by selected reaction monitoring via electrospray ionization source with positive ionization mode. An unpaired Student’s t-test was used for the statistical comparison of the main pharmacokinetic parameters. There were statistically significant differences (P < 0.05) in the pharmacokinetic parameters of puerarin-7-O-glucuronide, puerarin and daidzin involving the AUC, CL and Vd not only between normal rats and blood stasis rats after administration of total flavonoid from Gegen, but also between administration of total flavonoid from Gegen alone and in combination with total saponin from Sanqi in blood stasis rats. The results obtained suggest that the pharmacokinetic behavior of puerarin-7-O-glucuronide, puerarin and daidzin are changed when total flavonoid from Gegen was administered in blood stasis animals or in combination with total saponin from Sanqi.