Preparation, spectroscopy and molecular modelling studies of the inclusion complex of cordycepin with cyclodextrins.

The inclusion complexes of cordycepin with cyclodextrins (CDs) were prepared, the resultant complexes were characterised by UV-vis, FTIR, DSC, SEM, XRD, ESI-MS and proton nuclear magnetic resonance spectroscopy ((1)H NMR). The stoichiometry was established using a Job plot and the inclusion mechanism was clarified using molecular dynamic simulations. Molecular modelling calculations have been carried out to rationalise the experimental findings and predict the stable molecular structure of the inclusion complex. The stability of the inclusion complexes were confirmed by energetic and thermodynamic properties (ΔE, ΔH, ΔG and ΔS) and HOMO, LUMO orbital. The 1:1 binding model of complexes were visually proved by ESI-MS experiment. Our results showed that the purine group of cordycepin molecule was deeply inserted into the cavity of CDs.