Objective Cyclo-trans-4-L-hydroxyprolyl-L-serine(JBP485)is a dipeptide isolated from Laennec,and Laennec is a hydrolyzate of human placenta.Evidence has indicated that JBP485 exhibited potent anti-hepatitis activity.In this study,we developed a method for rapid and sensitive determination of JBP485 in rat biologic samples by LC/MS,and then studied its pharmacokinetics.We investigated the main excretion pathway of JBP485.Methods Following protein-precipitation with methanol,the analyte and internal standard(Paracetamol)were separated from rat plasma using an isocratic mobile phase on an Cap cell pack C18 UG120 column with a mobile phase consisting of methanol-water-formic acid(30∶70∶0.2,V∶V∶V)at a flow rate of 0.5 mL·min-1.An API 3200 tandem mass spectrometer equipped with Turbo Ion Spray ionization source was used as detector and was operated in the positive ion mode.Multiple reaction monitoring transporter precursor to product ion combinations of m/z 201.1→86.1 and m/z 152.1→110.1 were performed to quantify JBP485 and internal standard,respectively.After JBP485 was injected intravenously at a dose of 25 mg·kg-1 to rats,blood,bile and urine was collected at different time up to 8 h.The plasma concentration-time curve was plotted.The main pharmacokinetic parameters of JBP485 were obtained by 3P97 software.Results Linear calibration was generated over a concentration range of 0.1-200 μg·mL-1 for biologic samples by using LC/MS,with the lower limit of quantification of 0.1 μg·mL-1.Intra-and inter-days precision and accuracy were acceptable for all quality control samples.The mean recovery of JBP485 was above 90%,respectively.Pharmacokinetic parameters were estimated as follows:AUC(9103.96±513.85)μg·min·mL-1,t1/2β(77.98±4.06)min and CL(0.002±0.0001)mL·kg-1·min-1.The cumulative urinary excretion for 8 hours after administration was 30% of the dose.The cumulative biliary excretion for 8 hours after administration was 2%.Conclusions The LC/MS method was suitable for the pharamacokinetic study of JBP485 in rat with the advantages of specificity,sensitivity,accuracy and high speed.Renal excretion was the main excretive route of JBP485. Objective Cyclo-trans-4-L-hydroxyprolyl-L-serine (JBP485) is a dipeptide isolated from Laennec, and Laennec is a hydrolyzate of human placenta. Evidence has indicated that JBP485 exhibits potent anti-hepatitis activity. In this study, we developed a method for rapid and sensitive determination of JBP485 in rat biologic samples by LC / MS, and then studied its pharmacokinetics. We investigated the main excretion pathway of JBP485.Methods Following protein-precipitation with methanol, the analyte and internal standard (Paracetamol) were separated from rat plasma using an isocratic mobile phase on an Cap cell pack C18 UG120 column with a mobile phase consisting of methanol-water-formic acid (30:70:0.2, V:V:V) at a flow rate of 0.5 mL · Min -1.An API 3200 tandem mass spectrometer equipped with Turbo Ion Spray ionization source was used as detector and was operated in the positive ion mode. Multiple reaction monitoring transporter precursor to product ion combinations of m / z 201.1 → 86.1 and m / z 152. 1 → 110.1 were performed to quantify JBP485 and internal standard, respectively. After JBP485 was injected intravenously at a dose of 25 mg · kg-1 to rats, blood, bile and urine was collected at different time up to 8 h.The plasma concentration -time curve was plotted. The main pharmacokinetic parameters of JBP485 were obtained by 3P97 software. Results Linear calibration was generated over a concentration range of 0.1-200 μg · mL-1 for biologic samples by using LC / MS with the lower limit of Quantification of 0.1 μg · mL-1.Intra-and inter-days precision and accuracy were acceptable for all quality control samples. The mean recovery of JBP485 was above 90%, respectively. Pharmacokinetic parameters were estimated as follows: AUC (9103.96 ± 513.85 ) μg · min · mL-1, t1 / 2β (77.98 ± 4.06) min and CL (0.002 ± 0.0001) mL · kg-1 · min-1.The cumulative urinary excretion for 8 hours after administration was 30% of the dose . The cumulative biliary excretion for 8 hours after administration was 2%. Conclusions The LC / MS met hod was suitable for the pharamacokinetic study of JBP485 in rat with the advantages of specificity, sensitivity, accuracy and high speed. Renal excretion was the main excretive route of JBP485.