Spectrometric study on the interaction of sodium cholate aggregates with quercetin

Abstract In this work, the interaction between sodium cholate (NaC) aggregates and quercetin has been studied in pH 7.4 sodium phosphate buffer. Surface tension measurement reveals that the presence of quercetin leads NaC to have increased critical aggregation concentrations, owing to the electrostatic repulsion between negative charged NaC and anionic quercetin species. As NaC monomers gradually aggregate into dimers, primary and secondary micelles, quercetin mixed with NaC often gives higher intensities of absorption and fluorescence than free quercetin, which is explained in terms of the hydrophobic binding of quercetin with NaC. The measurement of quercetin anisotropy suggests that quercetin experiences a more hydrophobic microenvironment in NaC secondary micelles than those in NaC dimers and primary micelles. The binding constant of quercetin with NaC secondary micelles is found to be higher than the value of quercetin with NaC primary micelles, which is ten times that of quercetin with NaC dimers. Moreover, NaC secondary micelles are superior to NaC dimers and primary micelles for enhancing the radical scavenging ability of quercetin.