Theoretical study of the interactions of β-cyclodextrin with 2′-hydroxyl-5′-methoxyacetophone and two of its isomers

The inclusion process of 2′-hydroxyl-5′-methoxyacetophone (Hma) with β-cyclodextrin (β-CD), as well as their other seven possible interaction types, was investigated theoretically. The data suggest that: (1) the inclusion complex formed by Hma entering into the cavity of β-CD from its wide side (the secondary hydroxyl group side) is more stable than that from its narrow side (the primary hydroxyl group side); (2) the formation of the inclusion complex is predicted to be an enthalpy-driven process in gas phase and an enthalpy-entropy co-driven process in aqueous solution, which is in accord with the experimental results; (3) other different interaction types between Hma and β-CD should be also possibly found experimentally due to their negative binding energy (ΔE) though their distributions differ greatly. At last, comparative study of the interactions of β-CD with Hma and its two isomers, paeonol (Pae) and acetovanillone (Ace), are investigated and their obvious differences in binding energy and enthalpy change suggest that the β-CD could identify the three isomers.