Abstract
The inclusion of ${\beta}-cyclodextrin$ $({\beta}-CyD)$ with prothionamide in aqueous phase was investigated by circular dichroism(CD), ultraviolet (UV) absorption, and solubility technique. The results suggested that a region of drug chromophore was located within the asymmetric center of ${\beta}-cyclodextrin$. Solubility and spectral changes were quantitatively treated to obtain stoichiometric ratio, which was found to be 1 : 1, and formation constants which were determined by solubility, CD, and UV method were 257, 367, and 389 $M^{-1}$, respectively. Also, the formation constant of the inclusion complex was determined by CD method at various pH. The result was that $K_c$ depended upon the pH of medium, and this fact also supported that thioamide moiety was accomodated in the cavity of ${\beta}-cyclodextrin$.