Investigation of noncovalent interactions between some chiral compounds and cyclodextrins using capillary electrophoresis

The existence of asymmetric organic molecules has been known for humanity for a long time. Nowadays, up to 50% of pharmaceuticals in use are chiral molecules and most of them are used in the form of racemates, which consist of an equimolar mixture of enantiomers. Enantiomers are molecules which have the same structure but have a different spatial orientation of an atomic bonds. The enantiomers are mirror images to each other. Despite a similar structural formula in two-dimensional planes, enantiomers are characterized by different biological activity in the chiral environment: pharmacokinetics, toxicity and pharmacodynamics. Enantiomers differ from each other in their action on proteins, receptors, and enzymes, and their biological action on the body is determined by these factors. For this reason, some medicinal substances are produced in the form of a single enantiomer. Capillary electrophoresis is an electrokinetic method of separation of substances that is widely used to analyze also enantiomeric mixtures. The usage of chiral selectors provides the possibility for separation of enantiomers in capillary electrophoresis. Cyclodextrins are most frequently used chiral selectors in capillary electrophoresis. They enantioselectivity interact with enantiomers by forming a temporary transient noncovalent diastereomeric complex. The created complexes differ from each other in spatial orientation and thermodynamic properties These causes lead to electrophoretic mobility differences and chiral divisions. In the present study, the enantiomers of some chiral substances, specifically of chiral herbicides mecoprop and dichloroprop were separated in capillary electrophoresis using cyclodextrins as chiral selectors. Both, natural cyclodextrins and their derivatives were used as chiral selectors. Enantiomer migration order using different cyclodextrins was studied having in mind further investigation of the structural mechanisms of enantioselective binding of enantiomers with cyclodextrins.

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