糖肽大环抗生素作选择试剂的高效液相色谱和毛细管电泳的手性识别机理

万古霉素(vancomycin)、替考拉宁(teicoplanin)和瑞斯西丁素A(ristocetin A)等大环抗生素是在HPLC和CE中成功使用的新手性选择试剂。这3种选择试剂的对映识别机理与其分子结构密切相关。本文报道了替考拉宁中糖部分在氨基酸和非氨基酸分离中的作用,万古霉素和替考拉宁中糖苷配基上的最基本结合位点的确定,以及pH值、温度等实验条件和有机改性剂的性质等对保留值和识别机理的影响的研究成果,综述了它们在对映体分离中的应用。     

The Use of Antibiotics as Chiral Selectors in Capillary Electrophoresis: A Review

Chirality is becoming an essential issue in modern pharmaceutical research as regulatory agencies emphasize the safety and efficiency of enantiomers in drug development. The development of efficient and reliable chiral separation methods became a necessity in the last 30 years, and capillary electrophoresis (CE), due to its relatively low costs and “green” features, is attracting increased attention. Cyclodextrin (CD) and their derivatives are the most frequently used chiral selectors (CSs) in CE, however, the use of antibiotics as CSs represents an interesting alternative. Various classes of antibiotics (aminoglycosides, ansamycins, glycopeptides, lincosamides, macrolides, tetracyclines) have been used more or less successfully for the enantio-separation of pharmaceuticals. Antibiotics offer the possibility of a multitude of potential interactions (electrostatic, inclusion, hydrogen bonding, etc.) due to their chemical diversity, allowing the enantio-separation of analytes with a wide range of structural characteristics. This article aims to review the application of various classes of antibiotics in the CE enantio-separation of pharmaceuticals. Antibiotic physiochemical characteristics, variables impacting enantio-separation, advantages, and disadvantages when certain antibiotics are used as CSs in CE are also explored.     

新型高效液相手性固定相选择剂——大环抗生素

 综述了大环抗生素类手性固定相在高效液相中的应用和最新发展动态,根据其分子结构探讨了其手性分离的特点,并与其他类型的手性固定相进行了比较;共51篇。     

大环抗生素--毛细管电泳手性分离中一种新的手性选择剂

两种类型的大环抗生素对很多外消旋化合物具有显著的手性选择性且手性选择性相互补充:第一种类型含ansamycin (安沙霉素) 特别适合于阳离子外消旋化合物的分离;第二种类型含glycopeptide (糖肽)最适于阴离子的分离.介绍了大环抗生素的结构特征及手性识别机理,讨论了pH值、抗生素类型和浓度、电泳电解质浓度和化学性质、有机改性剂及胶束相等不同实验条件对分离的影响,还概述了几种大环抗生素作为手性选择剂,在毛细管电泳手性分离中的研究近况.     

Single Isomer N-Heterocyclic Cyclodextrin Derivatives as Chiral Selectors in Capillary Electrophoresis

In order to better understand the chiral recognition mechanisms of positively charged cyclodextrin (CD) derivatives, the synthesis, the pK_a determination by ¹H nuclear magnetic resonance (NMR)-pH titration and a comparative chiral capillary electrophoretic (CE) study were performed with two series of mono-substituted cationic single isomer CDs. The first series of selectors were mono-(6-N-pyrrolidine-6-deoxy)-β-CD (PYR-β-CD), mono-(6-N-piperidine-6-deoxy)-β-CD (PIP-β-CD), mono-(6-N-morpholine-6-deoxy)-β-CD (MO-β-CD) and mono-(6-N-piperazine-6-deoxy)-β-CD (PIPA-β-CD), carrying a pH-adjustable moiety at the narrower rim of the cavity, while the second set represented by their quaternarized, permanently cationic counterparts: mono-(6-N-(N-methyl-pyrrolidine)-6-deoxy)-β-CD (MePYR-β-CD), mono-(6-N-(N-methyl-piperidine)-6-deoxy)-β-CD (MePIP-β-CD), mono-(6-N-(N-methyl-morpholine)-6-deoxy)-β-CD (MeMO-β-CD) and mono-(6-N-(4,4-N,N-dimethyl-piperazine)-β-CD (diMePIPA-β-CD). Based on pH-dependent and selector concentration-dependent comparative studies of these single isomer N-heterocyclic CDs presented herein, it can be concluded that all CDs could successfully be applied as chiral selectors for the enantiodiscrimination of several negatively charged and zwitterionic model racemates. The substituent-dependent enantiomer migration order reversal of dansylated-valine using PIP-β-CD contrary to PYP-β-CD, MO-β-CD and PIPA-β-CD was also studied by ¹H- and 2D ROESY NMR experiments.     

Determination of Catecholamines by Capillary Electrophoresis and Reversed-Phase High-Performance Liquid Chromatography

A method is proposed for the electrophoretic determination of adrenaline, noradrenaline, and dopamine with mass-spectrometric or UV detection. A procedure is proposed for the sample preparation of biological fluids with the use of solid-phase extraction on alumina. A comparative assessment of the determination of catecholamines by capillary electrophoresis and reversed-phase high-performance liquid chromatography was performed.     

Mechanistic Principles in Chiral Separations Using Liquid Chromatography and Capillary Electrophoresis

Due to the importance of chiral separations of drugs, pharmaceuticals, agrochemicals and xenobiotics by high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), it is important to have the knowledge of the enantiomeric recognition mechanisms so that scientists may design and module the new chiral selectors for rapid, inexpensive and reproducible chiral separations; specially at preparative scale. The mechanisms of the chiral separation by HPLC and CE using polysaccharides, cyclodextrins, macrocyclic glycopeptide antibiotics, Pirkle type, ligand exchangers, crown ethers and other several types of chiral selectors have been discussed. Various complex formation and different types of interactions responsible for chiral resolution have been presented in detail.     

Enantioselective Liquid Chromatographic Separations Using Macrocyclic Glycopeptide-Based Chiral Selectors

Numerous chemical compounds of high practical importance, such as drugs, fertilizers, and food additives are being commercialized as racemic mixtures, although in most cases only one of the isomers possesses the desirable properties. As our understanding of the biological actions of chiral compounds has improved, the investigation of the pharmacological and toxicological properties has become more and more important. Chirality has become a major issue in the pharmaceutical industry; therefore, there is a continuous demand to extend the available analytical methods for enantiomeric separations and enhance their efficiency. Direct liquid chromatography methods based on the application of chiral stationary phases have become a very sophisticated field of enantiomeric separations by now. Hundreds of chiral stationary phases have been commercialized so far. Among these, macrocyclic glycopeptide-based chiral selectors have proved to be an exceptionally useful class of chiral selectors for the separation of enantiomers of biological and pharmacological importance. This review focuses on direct liquid chromatography-based enantiomer separations, applying macrocyclic glycopeptide-based chiral selectors. Special attention is paid to the characterization of the physico-chemical properties of these macrocyclic glycopeptide antibiotics providing detailed information on their applications published recently.     

基于环糊精手性选择剂的几种手性药物对映体的毛细管电泳拆分

以环糊精(-αCD、-βCD和-γCD)为手性选择剂,采用毛细管电泳对扑尔敏、异丙嗪和二氧异丙嗪对映体进行了分离,考察了手性选择剂的浓度、缓冲液pH值及有机添加剂对手性分离的影响,并就拆分机理进行了初步探讨.     

Chiral Discrimination of Mexiletine Enantiomers by Capillary Electrophoresis Using Cyclodextrins as Chiral Selectors and Experimental Design Method Optimization

Mexiletine (MXL) is a class IB antiarrhythmic agent, acting as a non-selective voltage-gated sodium channel blocker, used in therapy as a racemic mixture R,S-MXL hydrochloride. The aim of the current study was the development of a new, fast, and efficient method for the chiral separation of MXL enantiomers using capillary electrophoresis (CE) and cyclodextrins (CDs) as chiral selectors (CSs). After an initial CS screening, using several neutral and charged CDs, at four pH levels, heptakis-2,3,6-tri-O-methyl-β-CD (TM-β-CD), a neutral derivatized CD, was chosen as the optimum CS for the enantioseparation. For method optimization, an initial screening fractional factorial design was applied to identify the most significant parameters, followed by a face-centered central composite design to establish the optimal separation conditions. The best results were obtained by applying the following optimized electrophoretic conditions: 60 mM phosphate buffer, pH 5.0, 50 mM TM-β-CD, temperature 20 °C, applied voltage 30 kV, hydrodynamic injection 50 mbar/s. MXL enantiomers were baseline separated with a resolution of 1.52 during a migration time of under 5 min; S-MXL was the first migrating enantiomer. The method’s analytical performance was verified in terms of precision, linearity, accuracy, and robustness (applying a Plackett–Burman design). The developed method was applied for the determination of MXL enantiomers in pharmaceuticals. A computer modeling of the MXL-CD complexes was applied to characterize host–guest chiral recognition.     

Comparative Enantiomer-Resolving Ability of Coated and Covalently Immobilized Versions of Two Polysaccharide-Based Chiral Selectors in High-Performance Liquid Chromatography

The separation of enantiomers of over 175 randomly selected chiral acidic, basic, and neutral compounds was studied on 4 polysaccharide-based chiral columns made by coating or covalent attachment of cellulose 3,5-dichlorophenylcarbamate or amylose 3,5-dimethylphenylcarbamate on the surface of silica. Triscarbamate derivatives of cellulose or amylose were used for the preparation of coated-type columns, while in the case of covalently immobilized chiral stationary phases, the respective polysaccharides were not completely carbamoylated but only close to triscarbamates. It was found that this minimal difference in the chemical composition of the polysaccharide derivatives resulted in significantly different enantiomer-resolving ability for certain groups of chiral compounds while only marginally different for other chiral analytes. This potential difference between coated- and covalently immobilized versions of the “same” chiral selector must be considered in method development with these columns, as well as in method transfer between them.     

Enantioseparation of α-Amino Acids by Capillary Electrophoresis Using L-Cysteine-Modified Cyclodextrins as Chiral Selectors

Capillary electrophoresis (CE) is a powerful separation technique that was used in a wide range of analytical chemical applications. Cyclodextrins(CDs) are the most commonly used chiral selectors in chiral capillary electrophoresis at the present time. Under neutral conditions, however, native CDs are neutral and usually applicable only for the enantioseparation of charged analyses. To overcome this defect we modified α- and β-CD with a L-cysteine moiety and used the CD derivatives as chiral selectors for the separation of a-amino acid enantiomers by the ligand exchange mode.     

高效毛细管电泳法手性拆分奥昔布宁对映体

以羟丙基-β-环糊精（HP-β-CD）作为手性选择剂,采用毛细管区带电泳模式,对盐酸奥昔布宁对映体进行手性分离,比较了β-CD和 HP-β-CD之间对药品的分离能力,考察了手性选择剂的浓度、背景电解质的pH 值、柱温、分离电压和三羟甲基氨基甲烷（Tris）在背景电解质磷酸盐中的用量等因素对盐酸奥昔布宁对映体分离的影响,在优化条件下,使盐酸奥昔布宁对映体达到基线分离。结果表明该方法重现性好、简便、快捷、实用性强、具有良好的应用前景。     

Advances in the Use of Cyclodextrins as Chiral Selectors in Capillary Electrokinetic Chromatography: Fundamentals and Applications

Capillary electrokinetic chromatography is generally recognized as a versatile and robust capillary electromigration technique for the separation of enantiomers. In this mode, one or more chiral selectors are added to the background electrolyte acting as pseudostationary phases. Within the various chiral selectors that have been applied to enantioseparations in capillary electrokinetic chromatography, cyclodextrins are by far the most often used selectors because of their versatility, structural variety and commercial availability. This is reflected in the large number of applications of cyclodextrins to analytical enantioseparations that have been reported between January 2012 and July 2016, the period of time covered by this review. Many of these applications cover aspects of life sciences such as drug analysis, bioanalysis or food analysis. Despite the large number of commercially available cyclodextrins, new derivatives have been developed in order to achieve altered enantioselectivities or to further broaden the application range. Cyclodextrins have also been used to demonstrate the validity of theoretical models of electromigration as well as complex formation equilibria in enantioseparations. Finally, recent studies for an understanding of the molecular basis of the chiral recognition between cyclodextrins and the analytes are discussed.

     

二元手性选择体系毛细管电泳/电化学分离检测手性药物酚苄明对映体

采用羟丙基-β-环糊精(HP-β-CD)和羟丙基甲基纤维素(HPMC)组成的二元手性选择剂体系,以8mmol/L三羟甲基氨基甲烷(Tris) 10mmol/L柠檬酸(Cit) 10mg/LHPMC 25mmol/LHP-β-CD为电泳运行液,在熔融石英毛细管(50μmi.d.×45cm)中,分离电压 15kV,方波安培检测,手性药物酚苄明对映体获得良好的基线分离,线性检测范围为4～105μmol/L,检出限为1.5μmol/L。对影响灵敏度和分离度的电泳运行液组成、手性选择剂(HP-β-CD、HPMC)浓度以及进样方式和样品介质等进行了详细讨论。应用于市售盐酸酚苄明片剂中酚苄明对映体的分离检测,取得满意结果。     

脂质体在液相色谱和毛细管电泳中的应用

脂质体具有与细胞膜相似的封闭双层结构,是接近天然生物膜的理想模型。该文综述了脂质体的制备和性质表征方法,固定脂质体色谱用于药物在脂质体膜上的吸收和蛋白质与脂质体膜的相互作用研究,脂质体毛细管电泳在药物分离、蛋白质分离和蛋白质相互作用方面的应用研究。     

Determination of Neotame by High-Performance Capillary Electrophoresis Using ß-cyclodextrin as a Chiral Selector

An electrokinetic chromatographic method was developed for the chiral separation of neotame, a new high intensity artificial sweetener, using a chiral separating agent heptakis 2,3,6-tri-o-methylbetacyclodextrin. The purpose of this study was to better understand diastereomer-resolution interactions between neotame and the chiral separating agent. Molecular docking studies were performed to elucidate the mechanism of the separation. The optimum conditions were 50 mM phosphate buffer, pH 5.5, applied voltage 20 kV, cassette temperature of 30°C, and a 4 s sample injection time. The calibration curve showed good linearity (r² > 0.99) with recoveries for both diastereomers, ranging from 95.66–99.00% and the limits of detection for L,L-neotame and D,D-neotame were 0.01857 and 0.08214 mM, respectively. The developed method showed analytical precision with relative standard deviations (n = 5) of 1.20% and 1.17% with respect to migration time and peak area, respectively. A large difference in the interaction energies observed between the diastereomers represents a significant differentiation. The results showed that both electrostatic and hydrophobic interactions played a significant role in stabilizing their inclusion complexes and consequently supported the elution order based on their differential stabilities.     

高效毛细管电泳法手性分离伪麻黄碱

以三甲基-β-环糊精(TM-β-CD)为手性选择剂,用毛细管区带电泳法对手性药物伪麻黄碱进行了分离.系统地考察了不同的手性选择剂及其浓度、缓冲溶液的浓度和pH、分离电压等对分离的影响.结果发现,在Tris-H3PO4(10 mmo1.L-1 Tris,5 mmo1.L-1 H3PO4,PH 2.74)缓冲溶液中,TM-β-CD为15 mmo1.L-1,分离电压18 kV条件下,伪麻黄碱对映体在6 min内获得快速基线分离.由此建立了可靠、快速的分析方法.