Abstract

The formation of inclusion complexes between estradiol and β-cyclodextrin (CD), sulfobutyleter-β-CD (SBCD) and hydroxypropil-β-CD (HPCD) was studied by chronocoulometric and differential pulse voltammetry. In presence of CD there is a decrease of the cathodic peak current with the increase of the amount of CD. This decrease is due to the lower diffusion coefficient (D) of estradiol-cyclodextrin complex compared with the free guest. In absence of CD, an estradiol D value of 8.6 × 10 -6 ± 0.1 × 10 -6 cm 2 s -1 was obtained. The addition of CDs produced a maximum decrease of 20%, 22% and 30% in the diffusion coefficient with CD, SBCD and HPCD, respectively. Using the variation in D, association constants of 132 ± 18, 247 ± 32 and 276 ± 28 M -1 for CD, HPCD and SBCD were determined. © 2008.