Simultaneous Determination of Astragaloside-IV and Triptolide of Xinfeng Capsule in Rat Plasma by LC-MS/MS: Application to Pharmacokinetic Study

A sensitive and reliable ultra performance liquid chromatography-electrospray ionizationtandem mass spectrometry (LC-ESI-MS/MS) has been developed and validated for simultaneous determination of the constituents in rat plasma after oral administration of Xinfeng capsule. LC separation was achieved on a BEH C18 column (100 mm x 2.1 mm i.d., 1.7 mu m particle size) with gradient elution using a mobile phase consisting of methanol/water with 0.5 mM ammonium acetate at a flow rate of 0.3 mL/min. The detection was carried out by a triple-quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via polarity in positive ionization mode. Linear calibration curves were obtained over the concentration range of 2-64 ng/mL for astragaloside-IV and 2-1024 ng/mL for triptolide. The mean recovery of all the analytes ranged from 81.3 to 89.7%. The intra-and inter-day precision (RSD %) was within 9.7% and accuracy (RE %) ranged from -2.4 to 7.6%. Our method was successfully used for pharmacokinetic study of the above components in the Xinfeng capsule.