Molecular dynamics simulations and theoretical calculations of cyclodextrin-polydatin inclusion complexes

In our previous work, the PD/gamma-cyclodextrin complex was discovered to have higher calculated K-c and Gibbs free energy (Delta G(0)) values by the phase-solubility diagram method, and molecular dynamics (MD) simulations were carried out to investigate the structure and dynamics of the 1:1 inclusion complexes formed by beta- and gamma-cyclodextrins (CD) with PD in water. The simulation results indicated that gamma-CD provides the most stable inclusion complex of among all PD-CD complexes in this study. Similar to the MD results, the thermodynamics of the selected inclusion complex structure was calculated by semi-empirical (PM3) and DFT (B3LYP/6-31G) methods. The statistical thermodynamics calculations also suggested that orientation b (including in CD's cavity from the wide side) of the PD/gamma-CD inclusion complex is a favourable binding mode and in good agreement with the experimental and MD data. Most importantly, the simulation results of present study are in good agreement with the experimental data. (C) 2021 Elsevier B.V. All rights reserved.