Abstract
Aspirin, benzoic acid and p-hydroxybenzoic acid, all of which form intermolecularly hydrogen-bonded dimer structures in the crystalline form, were ground with α- or β-cyclodextrin. Inclusion compounds were also prepared by the coprecipitation method, except in the case of the aspirin-α-cyclodextrin system. The dispersed state of the medicinal molecules were investigated by analysis of the infrared spectra in the carbonyl stretching regions. It was suggested that the dispersed state of medicinals in the α-cyclodextrin system was different from that in the β-cyclodextrin system. It was assumed that, by grinding, aspirin molecules were included in the cyclodextrin cavity in the β-cyclodextrin system, but were dispersed monomolecularly in the hydrogen-bonded network structure of cyclodextrin in the α-cyclodextrin system. Interaction between medicinals and α- or β-cyclodextrin in aqueous solution was investigated by means of nuclear magnetic resonance studies. The sublimation of p-hydroxybenzoic acid from the ground mixtures or inclusion compounds with α- or β-cyclodextrin systems was determined by thermogravimetry. The effects of cyclodextrin on the hydrolysis of aspirin under acidic conditions were investigated as well.
