Nuclear magnetic resonance investigation of the stoichiometries in beta-cyclodextrin:steroid inclusion complexes

Nuclear magnetic resonance at high field has been used to investigate the stoichiometries of pharmacologically important beta-cyclodextrin:steroid complexes. This technique provides evidence for the existence of true inclusion complexes and allows unequivocal determination of the stoichiometry for complexes obtained in the solid state, as well as in solution. The present data clarify previously published determinations of the stoichiometry of these complexes and show the influence of the nature and position of functional groups on the molecular ratio in the complex. The observed behavior can be rationalized using representative steroids and allows prediction of the strength of inclusion and the most probable stoichiometry.