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 β-cyclodextrin (β-CD) was investigated using reversed-phase liquid chromatography and mobile phases to which β-CD was added. The decrease in the retention times with increasing concentrations of β-CD (0–2.5 mM) showed that trans-resveratrol forms a 1:1 complex with β-CD, while the apparent formation constants (KF) 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–β-CD interaction decreased when the temperature was raised from 20 to 37 °C. In order to gain information about the mechanism aspect of the trans-resveratrol affinity for β-CD, the thermodynamic parameters of the complexation were obtained. Complex formation of trans-resveratrol with β-CD (ΔG° = −17.01 kJ/mol) is largely driven by enthalpy (ΔH° = −30.62 kJ/mol) and slightly entropy changes (ΔS° = −45.68 J/mol K).