Dermatan sulfate as useful chiral selector in capillary electrophoresis

Antimalarial analysis of pharmaceutical formulations and biological samples by capillary electrophoresis: the state of the art and applications

Malaria is a serious public health problem, being an endemic disease in 84 countries, mainly in Africa. This review explores the application of capillary electrophoresis (CE) techniques for analyzing antimalarial drugs, highlighting methods from 2000 to 2023 for the analysis of pharmaceutical formulations and human biological samples. The versatility, selectivity, high efficiency, cost-effectiveness, and high analytical frequency of CE techniques have become attractive choices for pharmaceutical analysis, focusing on quality control and impurity analysis applications. The evolution of achiral and chiral electromigration methods has been described based on the features of each mode of separation: capillary zone electrophoresis (CZE), micellar electrokinetic chromatography, microemulsion electrokinetic chromatography, and capillary electrochromatography. As expected, CZE is reported in most articles owing to its compatibility with drug properties and separation mode. However, it is necessary to perform other separation modes for a few drugs that are present in neutral form. After exhaustive research using different databases and statistical analyses, 27 articles using CE techniques for antimalarial drug analysis were found and are mentioned in this review.

Immobilization of Chondroitin Sulfate A onto Monolithic Epoxy Silica Column as a New Chiral Stationary Phase for High-Performance Liquid Chromatographic Enantioseparation

Chondroitin sulfate A was covalently immobilized onto a monolithic silica epoxy column involving a Schiff base formation in the presence of ethylenediamine as a spacer and evaluated in terms of its selectivity in enantioseparation. The obtained column was utilized as a chiral stationary phase in enantioseparation of amlodipine and verapamil using a mobile phase consisting of 50 mM phosphate buffer pH 3.5 and UV detection. Sample dilution by organic solvents (preferably 25% v/v acetonitrile-aqueous solution) was applied to achieve baseline enantioresolution (Rs > 3.0) of the individual drug models within 7 min, an excellent linearity (R² = 0.999) and an interday repeatability of 1.1% to 1.8% RSD. The performance of the immobilized column for quantification of racemate in commercial tablets showed a recovery of 86–98% from tablet matrices. Computational modeling by molecular docking was employed to investigate the feasible complexes between enantiomers and the chiral selector.

Differential effects of organic modifiers on the enantioseparation of dimetindene maleate with carboxymethyl-β-cyclodextrin in capillary electrophoresis

Methanol enhances the enantioresolution of dimetindene enantiomers with carboxymethyl-beta-cyclodextrin (CMCD) as chiral selector at a concentration below its optimal value. The same effect was observed with ethanol (EtOH), although less pronounced. On the other hand, the addition of isopropanol (IP) or acetonitrile (ACN) decreases the enantioseparation. To elucidate the underlying mechanisms of these observed effects, other neutral (beta-CD, hydroxypropyl-beta-CD, and trimethyl-beta-CD) as well as chargeable (carboxyethyl-beta-CD and succinyl-beta-CD) CD derivatives were also tested with MeOH as organic modifier. It can be concluded that the increased enantioresolution of dimetindene enantiomers was only noted with CMCD as chiral selector and a short-chain organic modifier containing an alcohol function. The slight deprotonation of CMCD at pH 3.0 was only partly responsible for the high enantioselectivity and the 'favourable' effect of MeOH or EtOH. An important feature that can be concluded from these results is that for this particular analyte approximately the same resolution can be obtained with a lower CMCD concentration and the addition of some MeOH, compared to a MeOH free buffer.

Effect of structure modification of chondroitin sulfate C on its enantioselectivity to basic drugs in capillary electrophoresis

The effect of structure modification of chondroitin sulfate C on its enantioselectivity to several representative basic drugs in capillary electrophoresis was investigated. Chemical desulfation showed no remarkable decrease in selectivity, whereas depolymerization with chondroitinase ABC resulted in complete loss of selectivity. Comparison with chondroitin sulfate A indicated considerable decrease in selectivity with this isomer. The great retention of enantioselectivity in the desulfated derivative suggests that the selectivity comes from the difference of the magnitude of an interaction in the multipoint mechanism between a part of the drug molecule and a functional group in chondroitin sulfate C other than the sulfate group. The sulfate group is not considered to play a major role for chiral separation. The complete loss of selectivity by depolymerization is consistent with a general tendency of lower selectivity in smaller saccharides, and the priority of chondroitin sulfate C to chondroitin sulfate A suggests the importance of the hydroxyl group at C4 in the galactosamine residue. During the course of this work we observed heavy tailing of the peaks of basic drugs in some batches of uncoated fused-silica capillaries under acidic conditions and solved this problem by doubly coating capillaries with Polybrene followed by chondroitin sulfate C. On the other hand, we demonstrated the usefulness of a special technique which uses a short, wider bore PTFE tube-attached capillary for the study of the effect of depolymerization, in order to minimize sample amount.

Enantiomer separation by capillary electrophoresis utilizing carboxymethyl derivatives of polysaccharides as chiral selectors

Enantiomer separations of various drugs by capillary electrophoresis (CE) were investigated utilizing carboxymethyl (CM) derivatives of some polysaccharides. Three types of CM-polysaccharides, namely CM-dextran, -amylose and -cellulose were employed as chiral selectors in the CE enantiomer separation. Capability of enantiomer separation by these CM-polysaccharides was compared with that by polysaccharides without CM residues (i.e. native or neutral polysaccharides). Among three selectors employed, CM-dextran and -cellulose showed a relatively wide capability of enantiomer separation. Modification of polysaccharides seems to lead to the enhancement of the capability of enantiomer separation. Degree of substitution greatly affected the capability of enantiomer separation of these polysaccharide derivatives as in the beta-cyclodextrins derivatives.

Chiral separation by chromatographic and electromigration techniques. A review

This review gives a survey of different chiral separation principles and their use in high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography (TLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC) highlighting new developments and innovative techniques. The mechanisms of the different separation principles are briefly discussed and some selected applications are shown.

Enantiomer separation by capillary electrophoresis utilizing noncyclic mono-, oligo- and polysaccharides as chiral selectors

Various noncyclic mono-, oligo- and polysaccharides have been successfully used for enantiomer separation in the analytical sciences such as HPLC and capillary electrophoresis (CE). This review presents enantiomer separation by CE utilizing mainly polysaccharides as chiral additives. The operation conditions that affect the enantioselectivity are briefly discussed.

Enantioseparations in capillary electromigration techniques: recent developments and future trends

This review summarizes the current status of enantioseparations using capillary electromigration techniques and gives the authors insights on the selected fundamental aspects and future trends in this field. The most recent developments in the field of chiral separations using capillary electrophoresis (CE) and capillary electrochromatography (CEC) are summarized. The status of chiral electromigration techniques is evaluated tacking into account the most recent developments in related techniques such as chiral HPLC, GC and SFC.

Recent progress in chiral separation principles in capillary electrophoresis

This review summarizes recent developments in the field of chiral separations by electromigration techniques including capillary zone electrophoresis (CZE), capillary gel electrophoresis (CGE), isotachophoresis (ITP), electrokinetic chromatography (EKC), and capillary electrochromatography (CEC). This overview focuses on the development of new chiral selectors and the introduction of new techniques rather than applications of already established selectors and methods. The mechanisms of the different chiral separation principles are discussed.

Design of experiments for capillary electrophoretic enantioresolution of salbutamol using dermatan sulfate

Statistical experimental design was used for the optimization and for robustness evaluation of a capillary electrophoretic method developed for the enantioresolution of salbutamol. Dermatan sulfate was used as chiral selector. The goal of the study was to obtain an efficient and fast separation. An eight-run Plackett-Burman matrix was used during the optimization process for the screening of the factors and to adjust the experimental domain under study. Response surface methodology was adopted after the screening phase to obtain information about how the factors percentage of chiral selector, pH and voltage affected the considered responses resolution and analysis time. The Derringer desirability function, which makes it possible to combine results obtained for properties measured on different scales, was used to simultaneously optimize the two responses. Robustness testing was carried out using a Plackett-Burman matrix. The method was found robust as regards the response resolution while voltage and chiral selector were found to be critical factors for the robustness of analysis time response. The proposed CE method permitted the complete enantioseparation of racemic salbutamol and was applied to its chiral resolution in spiked urine samples.

Chiral resolution of basic drugs by capillary electrophoresis with new glycosaminoglycans

New glycosaminoglycans, fucose-containing glycosaminoglycan (FGAG) and depolymerized holothurian glycosaminoglycan (DHG), were investigated as chiral additives for the separation of drug enantiomers by capillary electrophoresis. The average molecular masses of FGAG and DHG were estimated to be about 59,000 and 14,000, respectively. A variety of basic drug enantiomers were resolved using 10 mM phosphate buffer, pH 5.0, containing 3% FGAG or DHG. Since chiral recognition properties of FGAG and DHG are different, some drug enantiomers were only separated by using FGAG or DHG. With regard to comparison of chiral recognition abilities of FGAG and DHG with other chiral selectors, tolperisone and eperisone enantiomers were not separated with alpha- or beta-cyclodextrin, or heparin as the chiral additives, but were separated with FGAG and DHG. The results obtained reveal that FGAG and DHG are useful as the chiral selectors for separations of drug enantiomers by CE, and that they could be complementarily used with other chiral additives.

Strategies for analysis and structure characterization of glycans/proteoglycans by capillary electrophoresis. Their diagnostic and biopharmaceutical importance

Proteoglycans are key biological macromolecules that, via their glycan constituents, participate and regulate several cellular events and physiopathological processes. Refined structures of their highly anionic glycan chains, involving sulphation pattern and uronic acid distribution through the polymeric chain, determine the interactions of proteoglycans with matrix effector molecules and are responsible for numerous effects. Analysis and structural characterization of glycans are, therefore, essential in understanding the biological functions of proteoglycans. Capillary electrophoresis with its high resolving power and sensitivity may successfully be used for the fine chemical characterization of components present in low amounts and to overcome limitations due to low amount/volume of biologic samples available. This technique is also friendly to the user and to the environment, since a very small amount of solvents (a few microL) is required. In this review the strategies used to analyse and characterize the structure of glycan chains of proteoglycans are summarized. They involve capillary electrophoretic analysis of depolymerized acidic glycan chains using specific enzymes and analysis of intact chains. The importance of this type of analysis in biologic samples and tissues and its possible diagnostic and biopharmaceutical use are also discussed.

Capillary electrophoresis of drugs: current status in the analysis of pharmaceuticals

The current status of capillary electrophoresis (CE) in pharmaceutical analyses is reviewed with about 300 references, mainly from 1996 until 1999. This article covers the use of CE for assay and purity determination of the main component, analysis of natural medicines, antisense DNA, peptides, and proteins. Analysis of hydrophobic and/or electrically neutral drugs by electrokinetic chromatography, capillary electrochromatography and nonaqueous CE is critically evaluated. Detailed techniques for the separation of enantiomers are given in the text with some actual applications. Furthermore, this review includes sensitivity and regulatory aspects for the actual use of CE in new drug applications (NDA). The analytical validation required for CE in NDA is also treated.

Semisynthetic chondroitins as chiral buffer additives in capillary electrophoresis

Chemically oversulfated galactosaminoglycans with potential as therapeutic agents (inhibitors of human leukocyte elastase) were tested as chiral selectors in capillary electrophoresis of basic racemates. The high anionic character of these compounds provides them with anodic mobility in acidic buffer; using uncoated capillaries, the enantioresolution of racemic basic drugs was obtained at pH 2.5. Dimethindene, chloroquine and chlorpheniramine were enantioresolved applying negative voltage (-15 kV) while the other analytes (propranolol, pindolol, tetrahydrozoline and cloperastine) exhibited catodic migration. The addition of organic solvents to the running buffer was evaluated in order to increase the resolution; methanol provides the best results and in general, baseline separation of the analytes was reached. The studied oversulfated mucopolysaccharide, shows the same ionic character of heparin but presents different stereochemistry and sites of sulfation. A comparison with heparin, used in the same acidic conditions, may underline the role of ionic, spatial and steric features of glycosaminoglycans in the enantiorecognition.