Abstract: AimTo study the pharmacokinetics of spinosin in rat plasma after oral administration of Suanzaoren extract using sulfamethoxazole (SMZ) as internal standard by RP-HPLC method. MethodsPlasma samples were deproteined with acetonitrile, followed by evaporation of the acetonitrile to dryness. The residual was then resolved in mobile phase and HPLC separation was achieved on a Hypersil C₁₈ (5 μm, 200 mm×4.6 mm ID) column at 35 ℃. The mobile phase consisted of acetonitrile-water-acetic acid (15∶85∶1) at a flow rate of 0.7 mL·min^-1. The UV detection wavelength was set at 334 nm. ResultsThe calibration curve was shown to be linear over the range from 18.1 to 903.5 μg·L^-1 (R²≥0.995). Mean recovery was 94.5%. Within-day and between-day precisions RSD were less than 9.0%. The limit of quantitation was 18.1 μg·L^-1. The plasma spinosin was stable at -20 ℃. ConclusionThe simple, sensitive and accurate HPLC method developed has been applied to determine the pharmacokinetics of spinosin in rat plasma after having taken Suanzaoren extract at a single dose.