Characterization of a novel hemi-acetone solvate form of erythromycin A thiocyanate

摘要

Erythromycin A thiocyanate, a salt form of erythromycin A, is a widely used veterinary medicine that has been shown to exhibit three pseudopolymorphic forms (hemitri(1.5) hydrated, dihydrated and trihydrated). These hydrated forms have been partially characterized in some patents, but a recently identified hemi-acetone solvate of erythromycin A thiocyanate was not explored previously. Characterization of the solvate, including determination of the crystal structure and emphasis the interaction between the solvent and non-solvated crystal molecules is significant as to understand, explain, and predict the behavior of the solvate during crystallization process. The solvated form was gained through slow evaporation crystallization method with the hydrate dissolved in acetone solution until the solution was saturated. In the present work, solvated samples of filtered and air-dried crystals were characterized using a range of solid-state analytical techniques including powder X-ray diffraction, Raman, thermogravimetric analysis, differential scanning calorimetry, and dynamic vapor sorption. These results can be used to determine key characteristics, such as desolvation enthalpies and desorption process. A through understanding of the characteristic of the hemi-acetone solvated erythromycin A thiocyanate will aid in understanding the interaction between erythromycin A thiocyanate and acetone solvent and predicting the behavior in acetone aqueous solution through anti-solvent crystallization.