Objective: To develop a sensitive and reliable ultra performance liquid chromatography tandem mass sepctrometry (UPLC-MS-MS) method for simultaneous determination and pharmacokinetics of gallic acid and paeoniflorin in rat plasma. Method: Following a protein precipitation with acetonitrile for plasma samples after iv Paeoniae Radix Rubra extract to rat. The analysis was achieved by BEH C18 (2.1 mm×50 mm

1.7 μm)column and the mobile phase was consisted of acetonitrile and water (both 0.1% formic acid included) follow step gradient elution. A TQD tandem mass spectrometry equipped with electrospray ionization source was used as detector and operated by multiple reaction monitoring (MRM) negative ion mode of the transitions m/z 169.0→125.0

m/z 525.1→449.1 for gallic acid and paeoniflorin

respectively. Result: Good linearity was achieved with concentration over the range of 0.056-41.2

0.36-265.1 mg·L-1 for gallic acid and paeoniflorin

the intra-and inter-day precisions were lower than 10.5%

while the low

mid and high concentration levels extraction recoveries were 87.5%

103.3%

89.5%

and 88.5%

105.0%

107.4% for gallic acid and paeoniflorin

respectively. The MRT of the two compounds were all blow 37 min in rats. Conclusion: The method was proved to be suitable for the pharmacokinetics of Paeoniae Radix Rubra extract

which offers advantages of rapid

high sensitivity and selectivity.