Determination of plasma protein binding rate both in Polygonum orientale L. extract and compound Hongcao freeze-dried powder for injection by equilibrium dialysis

OBJECTIVE To determine and compare the plasma protein binding rate of two kinds of compounds in the extraction of Polygonum orientale and compound Hongcao freeze-dried powder for injection by equilibrium dialysis method.METHODS Equilibrium dialysis method combined with liquid chromatography-tandem mass spectrometry(UPLC-ESI-MS/MS) was employed to determine the protein binding rate of protocatechuic acid,isoorientin with human plasma protein both in the extraction of Polygonum orientale and compound Hongcao freeze-dried powder and the binding characteristics were also calculated.RESULTS The results showed medium binding power of protocatechuic acid and high binding power of isoorientin to plasma protein,the powers of the two compounds with the plasma protein were independent on the area of the concentration which was determinate.In the compound Hongcao freeze-dried powder,the related binding characteristics of isoorientin had somewhat increase;and compared with the extraction of Polygonum orientale,there was also some difference.CONCLUSION The protein binding rates of the compounds in the Polygonum orientale were independent on the area of the concentration which was determinate,but there was some change when the herb was composed to compound preparation.