Characterisation of inclusion complex of trans-ferulic acid and hydroxypropyl-β-cyclodextrin

The inclusion complex of trans-ferulic acid (FA) with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was prepared by the freeze-drying method and its characterisation was investigated by different analytical techniques including UV-visible spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy. All these approaches indicated that FA was able to form an inclusion complex with HP-beta-CD, and the FA/HP-beta-CD inclusion compounds exhibited different spectroscopic features and properties from FA. The stoichiometry of the complex was 1:1. The calculated apparent stability constant of the FA/HP-beta-CD complex was 166.3 M-1, and the water solubility of FA was significantly improved by phase solubility studies. Moreover, the irradiation-induced decomposition of FA in aqueous solution was markedly reduced by complexation with HP-beta-CD. The results showed that HP-beta-CD was a proper excipient for increasing solubility and stability of FA. (C) 2010 Elsevier Ltd. All rights reserved.