Determination and Pharmacokinetic Study of Leonurine in Rat Plasma by Sensitive HPLC

OBJECTIVE To establish an HPLC method for determination of plasma concentration of leonurine (LE) and investigate its pharmacokinetics in rats. METHODS After oral administration of LE suspension (50 mg·kg^-1), plasma samples were collected at different points. After extracted from plasma by ethyl acetate, the plasma concentrations of LE and its internal standard (IS) n-benzoyl-L-arginine ethyl ester (BAEE) were determined by HPLC. Chromatographic separation was performed on a Diamonsil C₁₈(250 mm×4.6 mm, 5 μm) with UV detection at 277 nm, using acetonitrile-0.02 mol·L^-1 monopotassium phosphate (pH 3.0) (22:78) as mobile phase at 1.0 mL·min^-1 flow rate, and the column temperature was 35℃. The pharmacokinetic parameters were calculated by PKS 1.0 software program. RESULTS The linear calibration curve of LE was obtained in the concentration range of 0.05-1.5 μg·mL^-1(r=0.999 1), and the lower limit of quantitation(LLOQ) was 0.05 μg·mL^-1(RSD=12.8%, n=5); The absolute recovery in plasma was 76.5%-82.5%; Intra-day and inter-day relative standard deviations were both below 10%, with accuracy in the range 96.9%-104.9%. The QC plasma samples were stable through repeated three freeze/thaw cycles and under the frozen condition at -20℃ for 30 d. The process of LE in rat fit two-compartment open model, and the main pharmacokinetic parameters obtained were t_max=0.95 h, C_max=0.51 μg·mL^-1, t_1/2=3.64 h, AUC_0-t=1.56 μg·mL^-1·h^-1, AUC_0-∞=1.78 μg·mL^-1·h^-1. CONCLUSION The assay method is proved to be simple, sensitive, precise and reliable enough for the pharmacokinetics study of LE in rat after oral administration.