Determination of phillygenin in rat plasma by high-performance liquid chromatography and its application to pharmacokinetic studies.

The research group has been dedicated to the study of Fructus Forsythiae which was used widely in traditional Chinese medicines. And some research results have been accepted in Chinese Pharmacopeia. In a recent study, phillygenin was found to be a potential "metabolite" of phillyrin and the effective material of phillyrin may be changed according to the in vivo pharmacokinetic process. Therefore, a sensitive, specific, accurate, and reproducible reversed phase HPLC method for the determination of phillygenin in rat plasma was developed. Separation was achieved on a Hypersil ODS C18 column with UV detection at 277 nm. The good linear calibration curves ranged from 0.039 to 20 μg/mL with the limit of quantification estimated as 0.026 μg/mL. The intra- and inter-day precisions were in the range of 98-103 %. The average recoveries of phillygenin were 90.54, 92.47, and 92.15 % for phillygenin of 0.156, 1.25, and 10.0 μg/mL. And the Ruggedness of HPLC method was evaluated. The analytical method was also successfully applied to the pharmacokinetic study of phillygenin in rat for the first time. A rapid distribution was observed from the plasma concentration-time curves, and was followed by a quick elimination for phillygenin. The mean t 1/2z was 6.02, 5.62, and 5.79 min for 1.4, 2.8, and 5.6 mg/kg, respectively. The AUC (0-t) increased linearly from 166.29 to 332.48 mg/L min. All results indicated that, in the range of the doses examined, the pharmacokinetics of phillygenin in rat was based on first-order kinetics.