Inclusion of chrysin in β-cyclodextrin nanocavity and its effect on antioxidant potential of chrysin: A spectroscopic and molecular modeling approach

Chrysin is a naturally occurring flavone that possesses a wide range of important biological activities. beta-Cyclodextrin (beta-CD) on the other hand due to its property of encapsulating molecules that are hydrophobic in nature is widely applied as drug delivery vehicle. Here, we have investigated the inclusion of chrysin within beta-CD in aqueous solution using spectroscopic and theoretical methods. The stoichiometry of this inclusion complex was established to be equimolar (1:1) and its equilibrium constant was determined. Estimation of the thermodynamic parameters of the inclusion complex showed that it is an enthalpy driven process. Our observations also inferred that van der Waal's interaction and hydrogen bonding are the key interactions that prevail in the complex. The process of inclusion not only increased the solubility of chrysin but also its antioxidant potential, as inferred from ABTS radical scavenging assay. Theoretical calculations show that destabilization of HOMO energies account for the higher antioxidant potential of chrysin upon inclusion. Molecular docking of chrysin with beta-CD followed by molecular modeling of the obtained complexes yielded results consistent with our experimental observation. Combining our studies on solvatochromicity with cluster and interaction analyses, we suggest the preferred mode of inclusion to be through the A-ring of chrysin. (C) 2010 Elsevier B.V. All rights reserved.