Theoretical study of complexation of resveratrol with cyclodextrins and cucurbiturils: structure and antioxidative activity

Resveratrol is an outstanding natural antioxidant which is often found in a wide variety of plant species; its antioxidative activity has been recently reported as being influenced by complexation with macromolecules such as cyclodextrins (CDs). In this work, the complexation of resveratrol with CDs and cucurbiturils (CBs) has been studied by density functional theory calculations, the equilibrium geometries and the electronic structures of the complexes are investigated at the B3LYP/6-311G(d, p) level of theory, the antioxidative capabilities of the inclusion complexes have been elucidated based on H-atom transfer (HAT), sequential proton loss electron transfer (SPLET) and single electron transfer (SET) antioxidative mechanisms. The influence of inclusion complexation on the structure and antioxidative activity of resveratrol has been investigated. Our results show that resveratrol exhibits a non-planar geometry when it is included in CDs and CBs. Complexation of resveratrol with these two macromolecules results in negligible change in frontier orbital distribution, but distinct change in orbital energies. Different inclusion complexes and inclusion modes show different influences on 4'-OH bond dissociation enthalpy (4'-OH BDE), proton affinity (PA) and the electron transfer enthalpy (ETE) of the 4'-phenolate anion, and the ionization potential (IP) of resveratrol. Compared to cyclodextrins, cucurbiturils exhibit better performance in improving the antioxidative capacity of resveratrol.