Inclusion complexes of estrone and estradiol with beta-cyclodextrin: Voltammetric and HPLC studies
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The interaction of estrone and estradiol with beta-cyclodextrins (beta CD) was investigated by differential pulse voltammetry (DPV) and high-performance liquid chromatography (HPLC) in mixed media. The co-solvent influence on the tendency of these estrogens to form inclusion complexes with beta CD was examined. Thus, acetonitrile (MeCN) and ethanol (EtOH) were used in a mixed aqueous medium containing phosphate buffer. The association constant of the inclusion complexes (K-a) of estrone and estradiol with beta CD were determined in two different media by using both voltammetric and chromatographic techniques. Estradiol was found to bind to beta CD with higher affinities than estrone, irrespective of the medium. We have also found a clear influence of the co-solvent on the K. value, which means a competition of co-solvent molecules with estrogens for binding to the cavity of beta CD. Consequently, interaction between CD and the steroids is weakened when acetonitrile is used.