To determine the plasma protein binding rate of the nine compounds in Inula cappa extraction by the method of equilibrium dialysis. The proteins in plasma samples were precipitated by methanol, and the ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) was developed for determination of the concentrations of the nine active compounds, namely chlorogenic acid, scopolin, neochlorogenic acid, cryptochlorogenic acid, 1,3-O-dicaffeoylquinic acid, galuteolin, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, with the internal standard of puerarin. We found that all components have a good linearity(r≥0.999), and accuracy, precision, extraction recovery and stability conformed to the requirements of determination, without endogenous compounds disturbing within the range of optimum concentration. This suggested that the method was stable and reliable, and could be used for the determination of the plasma protein binding rates of the nine active compounds in rat and human plasma of I. cappa. The plasma protein binding rates of the nine active compounds in rat and human plasma respectively were(41.07±0.046)%-(94.95±0.008)%, and(37.66±0.043)%-(97.46±0.013)%. According to the results, there were differences in the plasma protein binding rates of the nine compounds in I. cappa extraction between rat and human.
Keywords: Inula cappa; caffeoylquinic acid; equilibrium dialysis; plasma protein binding rates.