Comparative pharmacokinetics study of a kaurane diterpenoid after oral administration of monomer and Siegesbeckiae pubescens Makino extract to rats

In this paper, a sensitive, rapid and reproducible high‐performance liquid chromatography–tandem mass spectrometry method was developed to analyze 16α‐hydro‐ent‐kauran‐17,19‐dioic acid in rat plasma. First, this study compared the pharmacokinetics of 16α‐hydro‐ent‐kauran‐17,19‐dioic acid after oral administration of monomer and Siegesbeckiae pubescens Makino extract in rat plasma with approximately the same dosage of 6.0 mg/kg. Second, chromatographic separation was performed on a Waters Symmetry C₁₈ column (2.1 × 100 mm, 3.5 µm) with isocratic elution using methanol–water containing 5 mmol/L ammonium acetate (70:30, v/v) as mobile phase at a flow rate of 0.2 mL/min. The calibration curves were linear over the range of 30–12000 ng/mL for monomer. At different time points (0, 0.083, 0.25, 0.75, 1, 2, 4, 6, 8, 12, 18, 24, 36, 48, 60 and 72 h) after administration, the concentrations of monomer in rat plasma were determined and main pharmacokinetic parameters were estimated. The double absorption presented in this study indicates that the pharmacokinetics of monomer in rat plasma have significant differences between different groups. Copyright © 2013 John Wiley & Sons, Ltd.