Abstract:7-ethyl-14-Aminocamptothecin (EAC) is a novel derivate of camptothecin which exhibits favorable antitumor activity.To determine the concentrations of the parent drug and lactam form metabolite (EAC-M) in vivo after intravenous administration of EAC,an UPLC-MS/MS method was established to simultaneously quantify EAC and EAC-M in SD rat plasma.7-ethyl-14-Nitrocamptothecin (ENC) and Chimmitecan (CMT) were used as internal standards.After protein precipitation by adding solution of internal standards and acetonitrile,plasma samples were separated on a Phenyl-Hexyl colum (2.1mm×50 mm,1.8 μm) with the mobile phase consisting of 0.5 mmoL/L ammonium acetate solution (containing 0.1% formic acid)-acetonitrile.Gradient elution was employed at a flow rate of 0.5 mL/min.Eluted compounds were ionized by an electrospray ionization source (ESI) in positive mode.The parent to production transitions for both the parent drug (m/z 392→291) and the metabolite (m/z 392→290) were monitored on a triple quadrupole mass spectrometer,using the multiple reaction monitoring (MRM).Based on the results from method validation,no interference was observed in blank plasma samples.The linear ranges for EAC and EAC-M were 0.500~250 ng/mL,the limits of quantitation were 0.500 ng/mL.The inter- and intra-day precisions (RSD) were not more than 7.6%,the accuracies (RE) were -4.2%~5.9%.The extraction recovery values were 84.4%~98.7%,and the matrix effects were 94.8%~104%.Samples beyond the upper limits of quantification were analyzed after a 6-fold-dilution with blank plasma,the precisions (RSD) were 1.8%,and the accuracies (RE) were -10%~-3.0%.In stability tests,the accuracies (RE) were -8.6%~11% and the precisions (RSD) were blow 7.2%.Data from pharmacokinetic tests indicated that EAC is moderately cleaned and is widely distributed in tissues.EAC-M was rapidly detected in plasma after intravenous administration which showed a 5% exposure of EAC.No accumulation of EAC or EAC-M was observed after an administration for 5 consecutive days.In summary,the provided method is convenient,sensitive,selective,and suitable for investigation of EAC and EAC-M in pharmacokinetic research.