Chiral separation and analysis of racemic pharmaceutical compounds like ofloxacin drug as model using crystal engineering methods and capillary electrophoresis

Abstract

Introduction: Chiral drugs often exhibit significant differences in pharmacological activity between their enantiomers, highlighting the importance of effective chiral separation to enhance therapeutic efficacy. Despite advances in this field, efficient methods for enantiomer separation remain a critical demand, especially for drugs like RS-Ofloxacin (RS-OFX), a chiral fluoroquinolone antibiotic which its S-enantiomer exhibits significantly higher potency- approximately 8–128 times greater- than the racemic mixture. This highlights the need to accurately separate the enantiomers.Objective: This study presents a new cocrystallization-based method for the precise and economical chiral separation of RS-OFX using amino acids by utilizing the formation of diastereomeric cocrystals.Method: Various amino acids were screened as potential coformers for cocrystal formation. Melting point data, FTIR Spectroscopy and Powder X-Ray Diffraction (PXRD) were conducted to identify the type of cocrystal. Capillary electrophoresis (CE) was employed to identify the most suitable solvent mixture for the separation of the diastereomeric pair. Enantioseparation was examined through evaporative crystallization in various solvent mixtures.Results: L-Glutamic acid (L-Glu) was identified as an appropriate coformer. Characterization methods confirmed the existence of a new solid state; consequently, diastereomeric cocrystals of R-OFX:L-Glu and S-OFX:L-Glu were successfully obtained. Theses diastereomeric cocrystals exhibited distinct solubility profiles in various solvent mixtures, enabling effective chiral separation through evaporative crystallization in methanol:chloroform (50:50, v/v) mixture, yielding 61.82% enantiomeric excess (ee) of the more active S-OFX:L-Glu. Conclusion: The results of this study suggest that the chiral resolution of racemic APIs through diastereomeric cocrystal formation with amino acids has the potential for scalability and adaptability in other APIs. This approach has the potential to be a valuable tool for the pharmaceutical industry in improving the efficiency of producing enantiopure pharmaceuticals.