Structural characterization and enantioseparation of the chiral compound praziquantel

In this study, we aimed to characterize the chiral compound type of a leading antischistosomal drug, praziquantel. The optically pure praziquantel enantiomers were recovered from the racemic mixture by enantiomeric separation, which was performed on preparative scale chromatography by using a novel β‐cyclodextrin type chiral column. The thermodynamic properties of praziquantel were determined from differential scanning calorimetry and the physical properties were studied by examining Fourier transform infrared spectroscopy and X‐ray powder diffraction. Based on the differential scanning calorimetry data, a melting point binary phase diagram was constructed. A ternary solubility phase diagram of praziquantel in methanol was also determined at the temperature of 0°C. All the experimental results support the conclusion that praziquantel is a racemic compound. The characterization of physical properties of praziquantel and the phase diagram are crucial for understanding the rationality for the successful resolution of praziquantel and also provide the basis for designing the strategy of separation and recovery of pure enantiomer. © 2004 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:3039–3046, 2004