New Methods For Enantioseparation Of Chiral Drugs By Capllary Electrophoresis

Many pharmaceutical compounds possess one or more chiral centers,different enantiomers often exhibit different pharmacological and toxicological properties.The investigation of the effective means to achieve stereoisomer separations continues to be of significant importance in the process of drug development.Over the last two decades capillary electrophoresis(CE)has been established as a very efficient technique for the separation of drug enantiomers,mainly due to its high efficiency,low consumption of sample,short analysis times,as well as low cost.Choosing the appropriate chiral selectors and additives is very important and difficult in developing a new effective method for enantioseparation of chiral drugs by capillary electrophoresis.In chiral CE separation,cyclodextrins(CDs)and their derivatives have been considered as the most widely used chiral selectors,because they can form inclusion complexes with a wide range of compounds.In recent years,increasing efforts have focused on ionic liquids(ILs),which can be combined with classical and economical enantiomeric selectors,β-cyclodextrin(β-CD)and derivativeβ-CD,in order to improve the enantioseparation performance.In this paper,different types of ILs were examined in combination with HP-β-CD to obtain simultaneous enantioseparation of four pairs of azole antifungal enantiomers,and the interactions between an IL and HP-β-CD or the analytes were studied using a neutral polyacrylamide coated capillary and 1H-nuclear magnetic resonance(NMR)spectroscopy to further explore the synergistic effect involved.The effect of ILs on the clathration of HP-β-CD with amlodipine was studied by using ultraviolet spectrophotometry method.A CE method has been developed for using N-methyl-N-ethylpyrrolidinium tetrafluoroborate(P12BF4)in combination with HP-β-CD as chiral selectors to enantioseparate eight chiral βagonists.Based on the CE separation study,we established a method to determine the enantiomeric purity of(-)-tratinterol in bulk drugs.A novel single-isomer amino acid modified CD,heptakis[2,6-di-O-(3-carboxymethylamino-2-hydroxypropyl)]-β-cyclodextrin(G-β-CD)was synthesized,and was applied as a chiral selector for enantioseparation of 15 drugs by CE for the first time.Additionally,computational modeling was used to investigate the recognition mechanism between G-β-CD and chlorpheniramine enantiomers.The research contents are as follows:1.Combined use of HP-β-CD and ILs for the simultaneous enantioseparation of four azole antifungals by CEThree different types of ILs,1-Ethyl-3-methylimidazolium-L-lactate([EMIm][L-lactate]),N-methyl-N-ethylpyrrolidinium tetrafluoroborate(P12BF4)and dodecyl trimethyl ammonium chloride(DTAC)were examined in combination with HP-β-CD to obtain simultaneous enantioseparation of four azole antifungals including miconazole,econazole,ketoconazole and itraconazole.The effects of the concentration,cations and anions of ILs on the enantioseparation were investigated.The interactions between DTAC and HP-β-CD were also studied using a neutral polyacrylamide coated capillary and 1H-nuclear magnetic resonance(NMR)spectroscopy to further explore the synergistic effect involved.The present work would be meaningful in exploring the mechanism of ILs improving the enantioseparation.2.Using ultraviolet spectrophotometry method to study the effect of ILs on the clathration of HP-β-CD with amlodipineBased on the study of enantioseparation of amlodipine by capillary electrophoresis,the ultraviolet spectrophotometry was used to determine the association constants of HP-β-CD with dl-and l-amlodipine,respectively.The effect of temperature and two ILs(P12BF4 and[EMIM][L-lactate])on association constants were investigated.And the thermodynamic parameters were calculated and were used to study the interactions between the host and guest moleculars.This method will provide a theoretical basis for studying the mechanism of inclusion effect and guiding separation experiments.3.Combined use of HP-β-CD and P12BF4 for the enantioseparation of eight chiral βagonistsA CE method had been developed for using P12BF4 in combination with HP-β-CD as chiral selectors to enantioseparate eight chiral β agonists,including salbutamol,trantinterol,clenbuterol,bambuterol,formoterol,terbutaline,tulobuterol and procaterol.The effects of HP-β-CD concentration,buffer concentration,buffer pH,and the concentration of P12BF4 were investigated and the optimized separation conditions were confirmed.The method is effective for enantioseparation of β agonists.4.Determination of the enantiomeric purity of(-)-tratinterol in bulk drugsBased on the CE separation study,we established a method to determine the enantiomeric purity of(-)-tratinterol in bulk drugs by validation in terms of sensitivity,linearity range,limits of detection and quantification,precision,repeatability and accuracy.The method was successfully applied for the enantiomeric impurity determination of(-)-tratinterol bulk samples synthesized by our school.The method is simple and rapid and the limit for the impurity,(+)-tratinterol,is set at not more than 0.2%.5.Enantioseparation of 15 chiral drugs using G-β-CD by capillary electrophoresis and theoretical study on chiral recognition mechanismA novel single-isomer amino acid modified cyclodextrin,heptakis(2,6-di-O-(3-carboxymethylamino-2-hydroxypropyl)-β-cyclodextrin,i.e.,glycine-β-cyclodextrin(G-β-CD)was synthesized,and was applied as a chiral selector for enantioseparation of 15 drugs by CE for the first time.The systematic method development approach was conducted by optimizing various operational parameters including pH,concentration of chiral selector and buffer,applied voltage and organic modifier.Additionally,a pair of chlorpheniramine enantiomers were selected as model compounds to study the host-guest interactions with G-β-CD through theoretical calculations by computational modeling.