Effects of grinding on physical and chemical properties of crystalline medicinals with microcrystalline cellulose. III. Infrared spectra of medicinals in ground mixtures.

Abstract

Several drugs, such as benzoic acid, aspirin, salicylic acid, and methyl p-hydroxy benzoate, all of which had intermolecular hydrogen bondings, were ground with microcrystalline cellulose respectively. Each drug was ground with β-cyclodextrin too. The inclusion compounds of each drug with β-cyclodextrin were prepared from aqueous solution. When the drugs were ground with β-cyclodextrin, rapid disappearance of X-ray diffraction peaks and that of heat of fusion of drugs, compared with microcrystalline cellulose, were observed. About the inclusion compounds, it was concluded from X-ray diffraction, thermal analysis, and ultraviolet measurements that β-cyclodextrin formed 1 : 1 adduct with each drug and the drug molecules were preffered oriented. The conditions of the drug molecules in the ground mixtures and in the inclusion compounds were investigated using infrared spectroscopy, especially by monitoring the carbonyl stretching bands near 1700 cm-1. When the dispersion of drugs into matrices were completed, the distinct frequency shift of the carbonyl stretching bands was observed in the infrared spectra of these sample. From these results, it would be reasonable to consider that in the ground mixture of microcrystalline cellulose, the drug molecules were present monomolecularly, presumably interacting with cellulose molecules by hydrogen bondings.