Investigation of a complex formation of dimethindene enantiomers with cyclodextrins using capillary electrophoresis and microcalorimetry

A chiral molecule is a type of molecule that has a non-superposable mirror image. The cause of chirality in molecules is the presence of an asymmetric atom– chiral center. A chiral molecule and its mirror image are called enantiomers. The enantiomers have same physical and chemical properties in achiral environment and only way to distinguish between them in such environment is the sign of rotation angle of polarized light. The identity of physical and chemical properties makes a separation of enantiomers as very challenging task. The chirality of a molecule may considerably affect its physiological activity. Many compounds of biological and pharmacological interest are chiral. Approximately 40% of the drugs in use are known to be chiral and only a small part of it are administered as pure enantiomers. Enantiomers differ from each other from the viewpoint of their absorption, distribution, protein binding, receptor affinity, transformation (metabolism) in the body and pharmacokinetics. The living body with its numerous homochiral compounds being amazingly chiral selector, will interact with each racemic drug differently and metabolize each enantiomer by a separate pathway to generate different pharmacological activity. Thus, one isomer may produce the desired therapeutic activities, while the other may be inactive or, in worst cases, produce undesired or toxic effects. Capillary electrophoresis is one of the youngest methods for separation of enantiomers, established as very popular tool in this field. The major reasons for such a popularity of CE is its own unique mechanism for separation of enantiomers. In addition, CE is highly efficient, very flexible and cost-effective technique. In the present study the enantiomer migration order (EMO) of Dimethindene Maleate in the presence of various cyclodextrins (CDs) was investigated by capillary electrophoresis (CE). Opposite EMO of Dimethindene maleate was observed when β-CD or heptakis (2,3,6-tri- methyl)-β-CD were used as the chiral selectors. The thermodynamic quantities of dimethindene interaction with cyclodextrins were determined by using isothermial titration microcalorimetry.

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