Sensitive analysis and pharmacokinetic study of the isomers paeoniflorin and albiflorin after oral administration of Total Glucosides Of White Paeony Capsule in rats

A sensitive and reliable method using liquid chromatography tandem mass spectrometry (LC–MS/MS) was established for the simultaneous assay of paeoniflorin and albiflorin in bio-samples of rats after liquid–liquid extraction with ethylacetate. For the first time, the developed method was validated and successfully applied to the pharmacokinetics study of paeoniflorin and albiflorin after oral administration of Total Glucosides Of White Paeony Capsule (TGP). Relative to the intravenous injection, the absolute bio-availabilities of paeoniflorin and albiflorin were 2.8 and 1.7%, while their excretion in feces was 43.06 and 40.87%, respectively. Both paeoniflorin and albiflorin showed dose-dependent exposure in plasma, with a half-life of approximately 1.8 h. No significant differences were observed between a single equal dose of paeoniflorin or albiflorin and that of TGP for the pharmacokinetic parameters, including AUC, T1/2 and Cmax. Paeoniflorin and albiflorin were exposed at high levels in immune relevant organ/tissues, such as the spleen, thymus and bone, which could facilitate immuno-regulatory activities.