Solvent-induced transformation of myo-inositol crystal

The objective of this study is to investigate the effect of organic solvents on pseudopolymorph transformation kinetics for clarifying the transformation phenomenon. In our previous study, we observed anhydrate and dihydrate crystals of myo-inositol in water and/or an ethanol-water system and transformation phenomena. However, we could not determine the detailed transformation mechanism in organic solvents. Therefore, we attempted adding seed crystals to different alcohol solvents, which resulted in the transformation of seed crystals of a dihydrate into anhydrate crystals. The transformation kinetics increased with a decrease in the alkyl carbon number in the solvents and also with an increase in the ethanol mass fraction. During the transformation process, fine anhydrate crystals were observed on the surface of dihydrate crystals, and the dihydrate crystals were found to dissolve and gradually decrease in size. On the basis of these results, we propose that the hydrophilic nature of organic solvents is a significant factor determining the pseudopolymorph transformation kinetics of myo-inositol. The transformation phenomena proceeded easily upon the addition of dehydrate seed crystals, as if the solvent had the driving force for the crystallization of a stable polymorph. We classified this unique mechanism as a ''solvent-induced transformation.''