Development and validation of an LC-MS/MS method for determination of compound K in human plasma and clinical application

A rapid, sensitive and selective analytical method was developed and validated for the determination of compound K, a major intestinal bacterial metabolite of ginsenosides in human plasma. Liquid-liquid extraction was used for sample preparation and analysis, followed by liquid chromatography tandem spectrometric analysis and an electrospray-ionization interface. Compound K was analyzed on a Phenomenex Luna C18 column (100×2.00 mm, 3 μm) with the mobile phase run isocratically with 10 mM ammonium acetate-methanol-acetonitrile (5:47.5:47.5, v/v/v) at a flow rate of 0.5 mL/min. The method was validated for accuracy (relative error <12.63%), precision (coefficient of variation <9.14%), linearity, and recovery. The assay was linear over the entire range of calibration standards i.e., a concentration range of 1 ng/mL to 1,000 ng/ mL (r² >0.9968). The recoveries of compound K after liquid-liquid extraction at 1, 2, 400, and 800 ng/mL were 106.00±0.08%, 103.50±0.19%, 111.45±5.21%, and 89.62±34.46% for intra-day and 85.40±0.08%, 94.50±0.09%, 112.50±5.21%, and 95.87±34.46% for inter-day, respectively. The lower limit of quantification of the analytical method of compound K was 1 ng/ mL in human plasma. The developed method was successfully applied to a pharmacokinetic study of compound K after oral administration in ten of healthy human subjects.