Chiral separation of rasagiline using sulfobutylether-β-cyclodextrin: capillary electrophoresis, NMR and molecular...

Pressure-assisted stereospecific capillary electrophoresis method was developed for the determination of enantiomeric purity of the antiparkinsonian agent (R)-rasagiline. The optimized method, 50 mM glycine-HCl buffer pH 2, supplied with 30 mM sulfobutylether-β-cyclodextrin, at 35°C, applying 12 kV in reversed polarity, and -8 mbar pressure (vacuum), short-end injection with -25 mbar × 2 s, was successful for baseline separation of rasagiline enantiomers (R_s = 3.5 ± 0.1) in a short analysis time. The method was validated according to current guidelines and proved to be reliable, linear, precise and accurate for determination of 0.15% S-enantiomer as chiral impurity in R-rasagiline sample, as well as quantification of the eutomer. Method application was tested on a commercial tablet formulation. Determination of spatial structure of diastereomeric associates was based on ¹ H and 2D ROESY NMR, indicating that the aromatic moiety of the molecule can enter the cyclodextrin cavity. NMR titration and molecular modeling revealed that S-rasagiline formed a more stable inclusion complex with sulfobutylether-β-cyclodextrin, than its antipode, which is in agreement with electrophoretic results.