Objective; To develop an LC-IT-MS/MS method for the determination of esculentoside A (EsA) in rat plasma and study the pharmacokinetics of EsA in SD rats. Methods; After liquid-liquid extraction (LLE) with n-buthanol, the analyte EsA and Rgl (internal standard) were separated on a Diamonsil C18(50 mm x 2. 1 mm, 3 μm) column with the mobile phase of methanol-water containing 0. 1% acetic acid (70: 30) at a flow rate of 0.2 mL·min . An ion trap mass spectrometer equipped with an electrospray ionization source performed in positive mode was used as the detector. The plasma concentration of EsA was determined by the developed LC-IT-MS/MS method, and its pharmacokinetic parameters were calculated by BAPP software. Results: Under the described LC-IT-MS/MS conditions, a good separation of EsA and IS was achieved and no significant endogenous interferences were observed. The calibration curves showed a good linearity over the range of 5 ~ 500 ng·mL-1with an average correlation coefficient of 0.998 3. The lower limit of quantitation of this method was 5 ng·mL -1 The extraction recovery of EsA from rat plasma was over 70% . Inter- and intra- precisions were all satisfactory as shown by RSDs lower than 10% . The main pharmacokinetic parameters after a single oral administration of 15 mg·kg~-1of EsA were summarized as follows:AUC0.24h was (1 013. 85 ±82. 73) ng·h·mL-1, AUC0_∞was ( 1 076. 31 ±92. 70)rnng·h·mL-1, tl/2 was (6.16 ±0.63) h, Cmix was (218. 80 ±38.33) ng·mL-1, Tmax was (0.8 ±0.1) h. Conclusion; The developed method is simple, rapid, sensitive enough and has been successfully applied to the pharmacokinetie study of EsA in SD rats.%目的:建立测定SD大鼠体内商陆皂苷甲(EsA)血药浓度的高效液相-离子阱串联质谱方法；研究EsA在SD大鼠体内的药动学特征.方法:采用Diamonsil C18色谱柱(50 mm×2.1 mm,3μm),流动相为甲醇-水(含0.1％冰醋酸)(70:30),流速为0.2 mL· min-1,采用ESI源,正离子检测模式,以人参皂苷Rg1为内标,血浆样品经正丁醇液液萃取后进样分析,测定大鼠血浆中EsA浓度,BAPP软件计算主要药动学参数.结果:在选定的色谱条件下,EsA和内标分离良好,没有内源性物质干扰.EsA在5～500 ng·mL-1范围内线性良好(r =0.998 3),最低定量限为5 ng· mL-1,提取回收率大于70％,日内和日间精密度小于10％.SD大鼠灌胃给予EsA 15 mg· kg-1后,其主要药动学参数AUC0～24h为(1 013.85 ±82.73) ng·h·mL-1,AUC0-∞为(1 076.31 ±92.70) ng·h·mL-1,t1/2为(6.16±0.63)h,Cmax为(218.80 ±38.33) ng·mL-1,Tmax为(0.8±0.1)h.结论:本方法简便快捷、灵敏准确；本研究所获得的EsA在SD大鼠体内的药动学参数为EsA的临床应用提供了依据.
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