Characterization of an inclusion complex of ethyl benzoate with hydroxypropyl-β-cyclodextrin.

The inclusion complex of ethyl benzoate with hydroxypropyl-β-cyclodextrin (HPCD) was prepared by a freeze-drying method and its characterizations were investigated by different analytical techniques including UV, FT-IR and phase solubility methods. All these approaches indicated that ethyl benzoate was able to form an inclusion complex with HPCD, and the ethyl benzoate/HPCD inclusion compounds exhibited different spectroscopic features and properties from ethyl benzoate. The stoichiometry of the complex was 1:1 and it was the benzene ring part of the ethyl benzoate molecule included into the HPCD cavities from the wider edge. The calculated apparent stability constant of the complex was 9485 M(-1). Moreover, the water solubility of ethyl benzoate was significantly improved by phase solubility studies. The release of ethyl benzoate was also regulated by the form of the inclusion complex. The results showed that HPCD was a proper excipient for increasing the solubility and controlled release of ethyl benzoate.