title: Separation and characterization of modified pregabalins in terms of cyclodextrin complexation, using capillary electrophoresis and nuclear magnetic resonance.
abstract: The (S)-(+)-isomer of 3-isobutyl-GABA (pregabalin), the blockbuster drug in the treatment of neuropathic pain has been separated from its R isomer by cyclodextrin modified capillary zone electrophoresis (CZE) using uncoated fused-silica capillary. Derivatization of the single isomer and the racemate with tosyl- and dansyl-chloride was carried out to introduce strong UV chromophores of different size. CE-pH titrations were performed to determine the dissociation constants for both derivatives. 30 cyclodextrin (CD) derivatives as chiral agents were used at four different pH values to study the enantioseparation of the differently protonated guest molecules. The separation was optimized as a function of CD concentration, buffer type and concentration, pH and applied voltage. For the tosylated derivate the best resolution (R(s)=2.76) was found with 6-monodeoxy-6-mono-(3-hydroxy)-propylamino-beta-cyclodextrin hydrochloride (PA-beta-CD) at pH 6.8, while with the same selector at pH 7.2 enantioseparation with an R(s) value of 4.32 could be achieved for the dansylated pregabalin. At pH 2.5 for the dansylated derivative trimethylated alpha- and beta-CD systems resulted the most significant separation (R(s)=7.38 and R(s)=7.74, respectively). Experiments with dual CD systems were carried out as well. The stoichiometry of the complexes was determined using the Job plot method and resulted in a 1:1 complex in both cases. The structures of the inclusion complexes were elucidated using 2D ROESY NMR experiments.
authors.affiliation: Semmelweis University, Department of Pharmaceutical Chemistry, Hogyes Endre u. 9, H-1092 Budapest, Hungary. beniszabi@gytk.sote.hu
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Béni
authors.forename: Tamás
authors.initials: T
authors.lastname: Sohajda
authors.forename: Gábor
authors.initials: G
authors.lastname: Neumajer
authors.forename: Róbert
authors.initials: R
authors.lastname: Iványi
authors.forename: Lajos
authors.initials: L
authors.lastname: Szente
authors.forename: Béla
authors.initials: B
authors.lastname: Noszál
mesh_terms: D000700:Analgesics / Q000737:chemistry / Q000302:isolation & purification*; D003505:Cyclodextrins / Q000737:chemistry*; D004340:Drug Contamination / Q000517:prevention & control; D019075:Electrophoresis, Capillary; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D000069583:Pregabalin; D012822:Silicon Dioxide / Q000737:chemistry; D013237:Stereoisomerism; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D000700:Analgesics; D003505:Cyclodextrins; D000069583:Pregabalin; D005680:gamma-Aminobutyric Acid; D012822:Silicon Dioxide