Inclusion complexes of bisphenol A with cyclomaltoheptaose (β-cyclodextrin):: solubilization and structure

The inclusion complexation behavior and the solubilization effects of Bisphenol A (BPA, an endocrine-disrupting chemical) by cyclomaltohexaose, -heptaose, and -octaose (alpha-, beta-, and gamma-cyclodextrins) were investigated by H-1 NMR spectroscopy and by elemental analysis. The results showed that beta- and gamma-cyclodextrins gave the satisfactory solubilization ability to BPA up to 7.2 x 10(3) mg L-1 and 9.0 x 10(3) mg L-1, respectively. X-ray crystallographic diffraction and ROESY spectroscopy were also employed to investigate the structure of the beta-CD/BPA inclusion complex in both aqueous solution and the solid state. The result showed that this complex adopted a 2:2 stoichiometry in the solid state, that is, a head-to-head beta-CD dimer accommodated two BPA molecules. The inclusion of BPA led to the desolvation of the beta-CD cavity and the destruction of the circularly closed hydrogen-bond network in the secondary side of beta-CD, which made the complex more soluble. (C) 2008 Elsevier Ltd. All rights reserved.