Determination of oxymatrine in human plasma by LC-MS and study on its pharmacokinetics

A sensitive and selective liquid chromatographic-mass spectrometric method is built to determine oxymatrine in human plasma. After a liquid-liquid extraction for samples, samples are analyzed on a C18 column interfaced with a mass spectrometer. Positive electrospray ionization is employed as the ionization source. The mobile phase is methanol-water containing 10 mmol/L ammonium acetate (60:40) at the flow rate of 0.8 mL/min. The method is linear in the concentration range of 10-1000 ng/mL. The lower limit of quantitation is 10 ng/mL. The intra- and inter-day relative standard deviation across three validation runs over the entire concentration range is less than 14.27%. The accuracy determined at three concentrations (20, 100, and 500 ng/mL for oxymatrine) is within +/- 10.0% in terms of relative error. The method herein described is successfully applied to the evaluation of pharmacokinetic profiles of oxymatrine tablets pills in 18 healthy volunteers. The results show AUC, Tmax, Cmax, and T1/2 between the testing formulation and reference formulation have no significant difference (P > 0.05). Relative bioavailability is 104.2 +/- 13.8%.