A deglucosylated metabolite of paeoniflorin of the root of Paeonia lactiflora and its pharmacokinetics in rats

Paeoniflorin is a bioactive monoterpene glucoside in Paeoniae Radix (PR), the roots of Paeonia lactiflora (Ranunculaceae). By oral administration to rats with the decoction of PR, the metabolism and pharmacokinetics of paeoniflorin were investigated in this study. A deglucosylated metabolite of paeoniflorin, paeoniflorgenin (PG), in serum was identified based on HPLC/MS and NMR spectral data. HPLC/UV methods were developed for determining PG in serum and feces suspension. A non-compartment model was used for the calculation of pharmacokinetic parameters. Moreover, the metabolism of paeoniflorin by various types of feces was investigated as well. The paeoniflorin levels in serum were below the detection limit throughout the study. The C (max), t (max), and AUC (0-t) of PG were 8.0 microg/mL, 10 min and 487.0 microg min/mL, respectively. Paeoniflorin was found to be hydrolyzed into PG through incubation with feces of rabbit, rat, pig or human. Similar profiles of PG were shown for various types of feces, except for rabbit. In conclusion, paeoniflorin was not absorbed per se, whereas its aglycone paeoniflorgenin was absorbable and circulating in the bloodstream. Rat and pig are appropriate models for investigating the metabolism and pharmacokinetics of paeoniflorin.