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

A simple high-performance liquid chromatography (HPLC) method is described for the determination of matrine in rat plasma. The plasma was deproteinized with acetonitrile that contained an internal standard (phenacetin) and was separated from the aqueous layer by adding sodium chloride. Matrine was extracted into the acetonitrile layer with high yield, and determined by reversed-phase HPLC (column: YMC-pack ODS-A, 5 μm, 150×4.6 mm, I.D.; eluent: acetonitrile–0.02 mol ammonium acetate buffer–triethylamine (35:65:0.035, v/v/v) and ultraviolet detection (220 nm). The limit of quantitation for matrine was 200 ng ml−1 in plasma, and the recovery was greater than 89%. The assay was linear from 0.5 to 50.0 μg ml−1. Variation over the range of the standard curve was less than 6%. The method was used to determine the concentration–time profiles of matrine in the plasma following oral administration of matrine aqueous solution or bolus injection from which the fractions of matrine reaching the systemic circulation were estimated by a deconvolution method for the first time.