Chiral capillary electrophoretic resolution of baclofen, gabaergic ligand, using highly sulfated cyclodextrins

Abstract

Using cyclodextrin-capillary zone electrophoresis (CD-CZE), baseline separation of baclofen, a potent GABA(B) agonist; was achieved. A method for the enantioresolution of this gamma-aminobutyric acid (GABA) and determination of enantiomeric purity was developed using CDs (highly sulfated-CD or highly S-CD) as chiral selectors and capillaries dynamically coated with polyethylene oxide (PEO). Operational parameters, such as the nature and concentration of the chiral selectors, buffer concentration, organic modifiers, and applied voltage, were investigated. The use of charged CDs provides a driving force in the opposite direction of the positively charged baclofen in the running buffer and enantiomeric resolution by inclusion of compounds in the CD cavity. Highly S-beta-CD was found to be the most effective complexing agent, allowing good enantiomeric resolution. The complete resolution was obtained using 25 mM phosphate buffer, pH 2.5, containing 3% w/v highly S-beta-CD at 25 degrees C with aN applied field of 0.40 kV/cm. The apparent association constants of the inclusion complexes were calculated. This optimized method was validated in terms of repeatability and limits of detection (0.13 microg x mL(-1)) and quantification. The migration order was determined.

Enantiomeric analysis of baclofen analogs by capillary zone electrophoresis, using highly sulfated cyclodextrins: Inclusion ionization constant pKa determination

“…The influence of the highly S-CD concentration (0.5 to 5%) on the separation is shown in Table 3. Chiral recognition was achieved for all concentrations tested with highly S-b-CD (compounds 1 [6] and 4) and highly S-a-CD (compounds 2 and 3) but only with high concentrations with highly S-b-CD for 3. Migration times (t) decrease sharply when the concentration of highly S-CD is increased from 0.5 to 2% (decrease of about 100%) and slowly from 2 to 5%.…”

“…They were discovered to be potent antagonists and are currently used as biological HPLC is one of the most appropriate techniques both in preparative (by furnishing both enantiomers) and analytical modes. In a recent paper [6], we cited in the references all the chromatographic separations of baclofen. We also described the analytical and/or preparative enantiospecific chromatographic separation of the antagonists 2, 3, 4 [7,8] with a chiral crown ether moiety (CR1) as chiral selector.…”

“…Numerous chiral separations were achieved with native, neutral, and charged (cationic and anionic) derivatized CDs [9], such as negatively charged highly sulfated CDs [10][11][12][13][14][15]. Recently [6], we developed a systematic approach for the separation of the enantiomers of baclofen (1) by CE using anionic CDs in acidic conditions. The influence of the nature and the concentration of the chiral selector, the use of an organic modifier, the concentration of the run buffer, and the separation voltage on the enantioresolution were discussed.…”

Chiral separations by capillary electrophoresis: Recent developments and applications

“…The same group investigated the chiral resolution of baclofen, using approximately the same methodology. Good enantiomeric separation was obtained using highly S-b-CD and a capillary dynamically coated with polyethylene oxide [152]. Zhou et al [153] investigated the chiral separation of a substituted imidazole p38 MAP kinase inhibitor and two intermediates with various sulfated-CDs.…”

Enantioseparation of baclofen with highly sulfated β‐cyclodextrin by capillary electrophoresis with laser‐induced fluorescence detection

“…For chiral analysis, different methods were developed such as GC with electron capture detection [26,27] as well as HPLC coupled with fluorescence [28,29], UV [30,31], and MS detection [32]. As reported in the literature, there are only few papers dedicated to the chiral separation of baclofen by CE with derivatized CDs [33] and crown ethers [34,35] in acidic media with UV detection. However, to our knowledge, there is only one study presenting LIF detection [36] and a-CD as chiral selector.…”