Determination of stoichiometric coefficients and apparent formation constants for β-cyclodextrin complexes of trans-resveratrol using reversed-phase liquid chromatography

The complexation of trans-resveratrol with beta-cyclodextrin (beta-CD) was investigated using reversed-phase liquid chromatography and mobile phases to which beta-CD was added. The decrease in the retention times with increasing concentrations of beta-CD (0-2.5 mM) showed that transresveratrol forms a 1: 1 complex with beta-CD, while the apparent formation constants (K-F) were strongly dependent of the water-methanol proportion of the mobile phase employed. A slight decrease in KF was observed at 50-55% water in the mobile phase but a large increase from 55 to 70% water. The values of KF for the trans-resveratrol-beta-CD interaction decreased when the temperature was raised from 20 to 37 degrees C. In order to gain information about the mechanism aspect of the trans-resveratrol affinity for P-CD, the thermodynamic parameters of the complexation were obtained. Complex formation of trans-resveratrol with P-CD (Delta G degrees = -17.01 kJ/mol) is largely driven by enthalpy (Delta H degrees = -30.620/mol) and slightly entropy changes (Delta S degrees = -45.68 J/mol K). (c) 2006 Published by Elsevier B.V.