Abstract: Objective To develop a high-sensitivity liquid chromatographic(UPLC) assay for determing the triptolide in rats plasma and to study the pharmacokinetics of triptolide in rats. Methods Sprague Dawley rats were given triptolide at the doses of 40 μg/kg and 200 μg/kg via oral administration and i.v. administration.The samples of plasma were collected at different times after administration and a ultra performance liquid chromatography-mass spectrometer/mass spectrometer(UPLC-MS/MS) was developed to determine the concentration of triptolide in biological samples.The plasma samples were extracted by ethylacetate and separated by a C18 reversed-phase column with a cycle time of 4 min. Results The linear range of 0.1-200.0 ng/mL, and lower limits of detection of 0.05 ng/mL and quantification of 0.1 ng/mL were established. This method was successfully applied to determine triptolide in rat plasma.The mean recovery was more than 95%. The relative standard deviation(RSD) of intra-day and inter-day were all less than 15%. After oral administration of triptolide with two dosages(40 and 200 μg/kg) to rats, the corresponding distribution half-time were 1.45, 3.05 h, respectively and the half-time of iv administration was 12.47 min.Conclusion This method is convenient, accurate and reliable. It can be used for determining the triptolide in rats plasma and pharmacokinetic studies

Key words: triptolide, ultra performance liquid chromatography-mass spectrometer/mass spectrometer(UPLC-MS/MS), plasma drug concentration, pharmacokinetics