[Simultaneous determination and pharmacokinetic studies of ferulic acid and paeoniflorin in human serum by high performance liquid chromatography after oral administration of Modified Xiao-yao Decoction].

Objective: To simultaneously determine the contents and explore the pharmacokinetics of ferulic acid and paeoniflorin by high performance liquid chromatography (HPLC) after oral administration of Modified Xiao-yao Decoction (MXYD), a compound of traditional Chinese herbal medicine.

Methods: A total of 8 healthy men were enlisted in this study. The serum samples were preprocessed by immersion method. The HPLC system was used to determine the contents of ferulic acid and paeoniflorin in the blood samples of the 8 healthy volunteers, and the blood was collected through the ulnar vein at 5 min, 10 min, 15 min, 30 min, 45 min, 1 h, 2 h and 3 h after MXYD administration. The dates of serum concentration-time were fitted by using the 3P97 analytical program of pharmacokinetics. The internal standard (IS) was coumarin. The detection wavelengths of paeoniflorin and ferulic acid were 230 nm from 0 min to 10 min and 320 nm from 10 min to 25 min respectively.

Results: After MXYD administration, paeoniflorin and ferulic acid were separated completely in the serum and no other interfering peaks were found in the spectrum of the chromatograms. The retention times of the paeoniflorin and ferulic acid were 8.02 min and 13.32 min respectively, and that of the coumarin was 19.14 min. The mean recovery rates of paeoniflorin and ferulic acid were 100.9% and 95.3% with relative standard deviation (RSD) of 3.2% and 3.4%, respectively. The calibration curve for paeoniflorin was linear over the concentration range 40-1 280 ng/ml. Its low-detection limit based on a signal-to-noise ratio of 3 was 5 ng/ml and low-concentration limit was 15 ng/ml with an RSD of 12.5%. Ferulic acid was in the range 10-320 ng/ml; its low-detection limit was 0.65 ng/ml and low-concentration limit was 5 ng/ml with an RSD of 9.7%. The method was found to be highly precise, with an RSD<5% and interday and intraday variability in the range of 92.1%-109.9% for each of the concentrations tested.

Conclusion: This is a study on simultaneously determining paeoniflorin and ferulic acid in serum of healthy volunteers after oral administration of MXYD. The assay is suitable for identifying the serum levels of ferulic acid and paeoniflorin in clinical investigations.