Insight into the structural deformations of beta-cyclodextrin caused by alcohol cosolvents and guest molecules.

Beta-cyclodextrin (β-CD) is an ideal candidate for a host molecule, and it is used as such in drug delivery and separation technology. The structural behavior of free β-CD and host-guest complexes of β-CD with two isoflavonoid isomers (puerarin and daidzin) in aqueous alcohol solutions, covering methanol, ethanol, 2-propanol, and 1-propanol, was investigated through molecular dynamics (MD) simulations. The MD results highlighted aspects of the structural flexibility and rigidity of β-CD in different alcohol solutions. The alcohol residence time within the β-CD cavity, solvent distribution around β-CD, and guest-induced structural changes were analyzed. Interaction with puerarin endowed β-CD with a more rigid structure than with daidzin and a weaker ternary complex β-CD/puerarin/alcohol was formed with a local participation of water molecules. The retention behavior of puerarin and daidzin on a β-CD-coupled medium was determined via chromatographic experiments and simulation results provided a structural explanation for such interactions.