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Maia PP, Nascimento CA, Silva CF, Nascimento Jr. CS. Chiral separation study of atenolol and carvedilol β-blocker drugs by DFT calculations. COMPUT THEOR CHEM 2022. [DOI: 10.1016/j.comptc.2022.113741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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2
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Bilonda MK, Mammino L. Computational studies of biologically active alkaloids of plant origin: an overview. PHYSICAL SCIENCES REVIEWS 2020. [DOI: 10.1515/psr-2019-0132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Computational studies nowadays constitute a crucial source of information for drug development, because they provide information on many molecular properties and also enable predictions of the properties of not-yet-synthesized compounds. Alkaloids are a vast group of natural products exhibiting a variety of biological activities, many of which are interesting for drug development. On the other hand, computational studies of biologically active alkaloids have so far mostly focused on few particularly relevant or “popular” molecules, such as quinine, caffeine, or cocaine, with only few works on the other molecules. The present work offers an overview of existing computational studies on alkaloid molecules, from the earliest ones to the most recent, and considering all the theoretical approaches with which studies have been performed (both quantum mechanics and molecular dynamics). The considered studies are grouped according to their objectives and outcomes, such as conformational analysis of alkaloid molecules, effects of selected solvents on their properties, docking studies aimed at better understanding of the interactions between alkaloid molecules and biological targets, studies focusing on structure activity relationships, and computational studies performed to confirm experimental results. It is concluded that it would be important that computational studies on many other alkaloid molecules are performed and their results made available, covering their different classes as well as the variety of their biological activities, to attain better understanding of the properties not only of individual molecules, but also of groups of related molecules and of the overall alkaloids family.
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Affiliation(s)
- Mireille K. Bilonda
- School of Mathematical and Natural Sciences, University of Venda , Thohoyandou , South Africa
- Faculty of Science, University of Kinshasa , Kinshasa , Democratic Republic of Congo
| | - Liliana Mammino
- School of Mathematical and Natural Sciences, University of Venda , Thohoyandou , South Africa
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3
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Silva CF, Nascimento TA, Guimarães L, Borges KB, Nascimento CS. Elucidation of the chromatographic enantiomer elution order for praziquantel: An experimental and theoretical assessment. Chirality 2020; 32:353-358. [DOI: 10.1002/chir.23164] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 12/17/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Camilla Fonseca Silva
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ), Campus Dom Bosco São João Minas Gerais Brazil
| | - Tienne Aparecida Nascimento
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ), Campus Dom Bosco São João Minas Gerais Brazil
| | - Luciana Guimarães
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ), Campus Dom Bosco São João Minas Gerais Brazil
| | - Keyller Bastos Borges
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ), Campus Dom Bosco São João Minas Gerais Brazil
| | - Clebio Soares Nascimento
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ), Campus Dom Bosco São João Minas Gerais Brazil
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4
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Computational studies in enantioselective liquid chromatography: Forty years of evolution in docking- and molecular dynamics-based simulations. Trends Analyt Chem 2020. [DOI: 10.1016/j.trac.2019.115703] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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5
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Silva CF, Guimarães L, Borges KB, Nascimento CS. Development and validation of an experimental and theoretical method for the chiral discrimination of dinotefuran. Chirality 2019; 32:53-63. [DOI: 10.1002/chir.23136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 09/09/2019] [Indexed: 02/06/2023]
Affiliation(s)
- Camilla Fonseca Silva
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ) São João Del Rei MG Brazil
| | - Luciana Guimarães
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ) São João Del Rei MG Brazil
| | - Keyller Bastos Borges
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ) São João Del Rei MG Brazil
| | - Clebio Soares Nascimento
- Departamento de Ciências Naturais (DCNAT)Universidade Federal de São João Del‐Rei (UFSJ) São João Del Rei MG Brazil
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6
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On the intermolecular interaction of N-benzylquininium chloride or quinine with some carbonyl group containing compounds. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.03.109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Marcelli T. Organocatalysis:
Cinchona
catalysts. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2011. [DOI: 10.1002/wcms.2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Tommaso Marcelli
- Dipartimento di Chimica, Materiali e Ingegneria Chimica ‘Giulio Natta’, Politecnico di Milano, Milan, Italy
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9
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Julínek O, Lindner W, Urbanová M. Study of stereoselective interactions of carbamoylated quinine and quinidine with 3,5-dinitrobenzoyl α-amino acids using VCD spectroscopy in the region of CH stretching vibrations. Chirality 2010; 23:354-60. [DOI: 10.1002/chir.20929] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 09/10/2010] [Indexed: 12/29/2022]
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10
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Al Azzam KM, Saad B, Adnan R, Aboul-Enein HY. Enantioselective analysis of ofloxacin and ornidazole in pharmaceutical formulations by capillary electrophoresis using single chiral selector and computational calculation of their inclusion complexes. Anal Chim Acta 2010; 674:249-55. [DOI: 10.1016/j.aca.2010.06.046] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 06/14/2010] [Accepted: 06/27/2010] [Indexed: 10/19/2022]
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11
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Zhang L, Sun Y. Molecular simulation of adsorption and its implications to protein chromatography: A review. Biochem Eng J 2010. [DOI: 10.1016/j.bej.2009.12.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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12
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Julínek O, Krupička M, Lindner W, Urbanová M. Enantioselective interaction of carbamoylated quinine and (S)-3,5-dinitrobenzoyl alanine: theoretical and experimental circular dichroism study. Phys Chem Chem Phys 2010; 12:11487-97. [DOI: 10.1039/c000046a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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13
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Lämmerhofer M. Chiral recognition by enantioselective liquid chromatography: mechanisms and modern chiral stationary phases. J Chromatogr A 2009; 1217:814-56. [PMID: 19906381 DOI: 10.1016/j.chroma.2009.10.022] [Citation(s) in RCA: 516] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 09/30/2009] [Accepted: 10/07/2009] [Indexed: 11/19/2022]
Abstract
An overview of the state-of-the-art in LC enantiomer separation is presented. This tutorial review is mainly focused on mechanisms of chiral recognition and enantiomer distinction of popular chiral selectors and corresponding chiral stationary phases including discussions of thermodynamics, additivity principle of binding increments, site-selective thermodynamics, extrathermodynamic approaches, methods employed for the investigation of dominating intermolecular interactions and complex structures such as spectroscopic methods (IR, NMR), X-ray diffraction and computational methods. Modern chiral stationary phases are discussed with particular focus on those that are commercially available and broadly used. It is attempted to provide the reader with vivid images of molecular recognition mechanisms of selected chiral selector-selectand pairs on basis of solid-state X-ray crystal structures and simulated computer models, respectively. Such snapshot images illustrated in this communication unfortunately cannot account for the molecular dynamics of the real world, but are supposed to be helpful for the understanding. The exploding number of papers about applications of various chiral stationary phases in numerous fields of enantiomer separations is not covered systematically.
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Affiliation(s)
- Michael Lämmerhofer
- Christian Doppler Laboratory for Molecular Recognition Materials, Department of Analytical Chemistry and Food Chemistry, University of Vienna, Waehringer Strasse 38, A-1090 Vienna, Austria.
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14
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Del Rio A. Exploring enantioselective molecular recognition mechanisms with chemoinformatic techniques. J Sep Sci 2009; 32:1566-84. [DOI: 10.1002/jssc.200800693] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Del Rio A, Gasteiger J. Encoding Absolute Configurations with Chiral Enantiophore Descriptors. Application to the Order of Elution of Enantiomers in Liquid Chromatography. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/qsar.200810066] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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16
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17
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Enantioselective complexation of carbamoylated quinine and quinidine with N-blocked amino acids: vibrational and electronic circular dichroism study. Anal Bioanal Chem 2008; 393:303-12. [DOI: 10.1007/s00216-008-2323-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 07/26/2008] [Accepted: 07/28/2008] [Indexed: 10/21/2022]
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18
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Kang GW, Ko JH, Cheong WJ. A Simplified Molecular Mechanics Calculation of Enantioseparation of Arylpropionic Acids in Chirex 3001 Stationary Phase. J LIQ CHROMATOGR R T 2007. [DOI: 10.1081/jlc-200038568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Gyoung Won Kang
- a Department of Chemistry and Institute of Basic Research , Inha University , Incheon, 402‐751, South Korea
| | - Joung Ho Ko
- a Department of Chemistry and Institute of Basic Research , Inha University , Incheon, 402‐751, South Korea
| | - Won Jo Cheong
- a Department of Chemistry and Institute of Basic Research , Inha University , Incheon, 402‐751, South Korea
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19
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Lämmerhofer M, Franco P, Lindner W. Quinine carbamate chiral stationary phases: Systematic optimization of steric selector-selectand binding increments and enantioselectivity by quantitative structure-enantioselectivity relationship studies. J Sep Sci 2006; 29:1486-96. [PMID: 16894794 DOI: 10.1002/jssc.200600111] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A series of quinine carbamate-based chiral stationary phases (CSPs) differing solely in the carbamate residue have been devised and a congeneric set of N-3,5-dinitrobenzoyl (DNB) amino acids (AAs) was separated into enantiomers on these CSPs by HPLC using a buffered hydro-organic mobile phase. Some details on retention and chiral recognition mechanisms have been investigated by application of quantitative structure-property relationship (QSPR) studies using the linear free energy relationship methodology, i.e., the extrathermodynamic approach. Retention factors of the high affinity enantiomer (log k2) and enantioselectivities (log alpha) were correlated with Taft's steric parameter as structural descriptor for the variability in the carbamate and AA residues, and statistically significant QSPR models could be obtained. They confirmed that the variance in the dependent variable (log k2, log alpha) is mainly associated with the steric bulkiness of the selectors' carbamate and of the AA residues. The retention factor of the second eluted enantiomers and the enantioselectivity first increased with steric bulkiness of the carbamate and AA residues, which may be explained by stronger dispersive interactions. After reaching an optimum, the dependent variable, however, declined with further increase of the steric bulkiness of the substituents, probably because of steric hindrance. The variability of the retention factors of the first eluted enantiomer could not be explained by steric descriptors. Instead, it has become obvious that the retention arises mainly from interactions of the DNB-AA and the quinine carbamate backbone, as it turned out to be more or less constant and solely to a minute amount modulated by the carbamate residue and the AA side chain. The QSPR models were fully in agreement with an earlier postulated chromatographically and spectroscopically derived hypothetical selector-selectand binding model.
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Affiliation(s)
- Michael Lämmerhofer
- Christian Doppler Laboratory for Molecular Recognition Materials, Department of Analytical Chemistry, University of Vienna, Vienna, Austria.
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20
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Kaufman TS, Rúveda EA. The quest for quinine: those who won the battles and those who won the war. Angew Chem Int Ed Engl 2006; 44:854-85. [PMID: 15669029 DOI: 10.1002/anie.200400663] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
For a long time, the synthesis of quinine constituted an elusive target. In 2004, which marked the 60th anniversary of the publication of the approach used by Woodward and Doering to synthesize quinine, two new stereocontrolled total syntheses of the natural product were accomplished. Together with the well-publicized first stereocontrolled total synthesis of quinine by Stork in 2001, these publications evidence the revival of interest of organic chemists in the synthesis of this compound, once considered a miracle drug. The recently disclosed syntheses of quinine also testify in a remarkable manner the huge progress made by organic synthesis during the last three decades since the first series of partially controlled syntheses of quinine by the group of Uskokovic. Following an account of the historical importance of quinine as an antimalarial drug and a brief description of the experiments which contributed to its isolation and structural elucidation, the first reconstructions of quinine and the total syntheses of the natural product are discussed.
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Affiliation(s)
- Teodoro S Kaufman
- Instituto de Química Orgánica de Síntesis (CONICET-UNR), Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina.
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22
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Abstract
Molecular Chirality is of central interest in biological studies because enantiomeric compounds, while indistinguishable by most inanimate systems, show profoundly different properties in biochemical environments. Enantioselective separation methods, based on the differential recognition of two optical isomers by a chiral selector, have been amply documented. Also, great effort has been directed towards a theoretical understanding of the fundamental mechanisms underlying the chiral recognition process. Here we report a comprehensive data examination of enantio separation measurements for over 72000 chiral selector-select and pairs from the chiral selection compendium CHIRBASE. The distribution of alpha = k'(D)/k'(L) values was found to follow a power law, equivalent to an exponential decay for chiral differential free energies. This observation is experimentally relevant in terms of the number of different individual or combinatorial selectors that need to be screened in order to observe alpha values higher than a preset minimum. A string model for enantiorecognition (SMED) formalism is proposed to account for this observation on the basis of an extended Ogston three-point interaction model. Partially overlapping molecular interaction domains are analyzed in terms of a string complementarity model for ligand-receptor complementarity. The results suggest that chiral selection statistics may be interpreted in terms of more general concepts related to biomolecular recognition.
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Affiliation(s)
- Ran Kafri
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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23
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Abstract
A systematic and comprehensive study of the conformational spaces of the Cinchona alkaloids quinine, quinidine, cinchonine, cinchonidine, epiquinine, epiquinidine, epicinchonine, and epicinchonidine using the semiempirical PM3 method is described. The results were analyzed in terms of syn/anti and open/closed/hindered and alpha/beta/gamma conformations. Special emphasis was given to the torsion angles T(1) (C(4a')-C(4')-C(9)-C(8)), T(2) (C(4')-C(9)-C(8)-N(1)) and T(3) (H-O(9)-C(9)-C(8)) that define the backbone and the hydroxy conformation, respectively. The results reveal the quasi-enantiomeric relationships between quinine and quinidine and between epiquinine and epiquinidine, and the main structural differences that exist between the therapeutically active Cinchona alkaloids, quinine and quinidine, and their inactive epimers, epiquinine and epiquinidine. The lowest energy conformation of quinine and quinidine is anti-closed-alpha. The lowest energy conformations of epiquinine and epiquinidine are anti-open-beta and anti-open-alpha, respectively. Low energy conformations with an intramolecular hydrogen bond (N(1.)H(.)O(9)) were found in epiquinine (the global minimum) and epiquinidine, but not in quinine and quinidine.
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Affiliation(s)
- Hava Caner
- Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel
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24
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C11 versus C9 carbamoylation of quinine: a new class of versatile polyfunctional chiral solvating agents. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0957-4166(03)00215-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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25
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McCalley DV. Analysis of the Cinchona alkaloids by high-performance liquid chromatography and other separation techniques. J Chromatogr A 2002; 967:1-19. [PMID: 12219924 DOI: 10.1016/s0021-9673(01)01557-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Cinchona alkaloids, which include the pharmaceuticals quinine and quinidine, continue to have a wide variety of important uses. A number of different chromatographic procedures have been developed for the qualitative and quantitative analysis of these compounds in a variety of sample matrices. Reversed-phase HPLC using ODS columns in combination with acidic mobile phases, and UV detection, is the most widely used method. Nevertheless, precautions need to be taken due to the strong silanophilic interactions which can occur with these analytes and the column surface, which can lead to poor peak shape and resolution. Different selectivity may be achieved in HPLC separations by use of alternative stationary phases, or by varying mobile phase pH. The specificity of detection systems may be improved by use of photodiode array UV detectors, or especially mass spectrometers. Thin-layer chromatography (TLC) provides a cheap alternative analytical method, which is especially useful for qualitative analysis. High-performance TLC, gas chromatography, capillary electrophoresis and capillary electrochromatography are all methods which after some development, could prove useful for Cinchona alkaloid separations.
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Affiliation(s)
- David V McCalley
- Faculty of Applied Sciences, University of the West of England, Frenchay, Bristol, UK.
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26
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Zarbl E, Lämmerhofer M, Franco P, Petracs M, Lindner W. Development of stereoselective nonaqueous capillary electrophoresis system for the resolution of cationic and amphoteric analytes. Electrophoresis 2001; 22:3297-307. [PMID: 11589294 DOI: 10.1002/1522-2683(200109)22:15<3297::aid-elps3297>3.0.co;2-b] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A stereoselective ion-pair nonaqueous capillary electrophoresis (NACE) method employing the partial filling technique with N-derivatized amino acids, e.g., (R)- and (S)-3,5-dinitrobenzoyl-leucine (DNB-Leu), as chiral selector for the separation of "pseudoenantiomeric" cinchona alkaloid derivatives and other structurally related basic compounds like the enantiomers of mefloquine is presented. Originating from NACE with cinchona alkaloid derivatives as chiral counterions, this method was developed by application of the reciprocity principle of chiral recognition, which was proven to be valid for stereoselective ion-pair capillary electrophoresis (CE). A variety of basic and amphoteric selectands (SAs) could be well resolved. Thereby, the separation was primarily based on stereoselective ion-pair formation of corresponding SA stereoisomers and mobility differences of free and complexed (ion-paired) SAs. Additionally, in the case of diastereomeric SAs, naturally existing mobility differences between the diastereomers played also a role, but was shown by control experiments with racemic DNB-Leu and without selector (SO) to be of minor contribution to overall separation selectivity. Due to its simplicity, speed, and good reproducibility, the established method can be utilized for fast screening of cationic as well as amphoteric chiral compounds, and therefore is a valuable tool in the development of new chiral selectors and chiral stationary phases. Small sample amounts of the SO (4-5 mg) and only analytical amounts of SAs are needed, and about 20-50 compounds per day can be tested.
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Affiliation(s)
- E Zarbl
- Institute of Analytical Chemistry, University of Vienna, Austria
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27
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Versatile chiral auxiliaries for NMR spectroscopy based on carbamoyl derivatives of dihydroquinine. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0957-4166(01)00349-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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28
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Lämmerhofer M, Zarbl E, Lindner W. Tert.-butylcarbamoylquinine as chiral ion-pair agent in non-aqueous enantioselective capillary electrophoresis applying the partial filling technique. J Chromatogr A 2000; 892:509-21. [PMID: 11045508 DOI: 10.1016/s0021-9673(00)00172-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The potential of tert.-butylcarbamoylquinine as chiral selector (SO) added to a non-aqueous background electrolyte for the capillary electrophoretic separation of the enantiomers of N-derivatized amino acids (selectands, SAs) is evaluated. Separation is based on different ion-pair formation equilibrium constants of (R) and (S) enantiomers of the negatively charged chiral analytes with the positively charged quinine-derived chiral SO and on mobility differences of free and complexed SAs, so that differences in the overall migration behavior of the SA enantiomers result. To suppress problems associated with the high UV absorption of the chiral SO and thus the high detector background in the 'total filling technique', the 'partial filling technique' has been adopted. Several parameters including filling time and length of SO zone, respectively, SO concentration, type of background electrolyte, have been evaluated. Using such an optimized method, for example, (R) and (S) enantiomers of 2,4-dinitrophenyl (DNP)-protected proline could be separated with alpha=1.08, R(S)=6.60, and N=130,000 theoretical plates within 15 min. Similar alpha values, resolution, and efficiencies were observed for other DNP-protected, as well as for diverse, N-derivatized amino acids like N-benzoyl, N-9-fluorenylmethoxycarbonyl, N-3,5-dinitrobenzyloxycarbonyl amino acids. A repeatability study clearly validated the robustness of the method and revealed its practical applicability.
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Affiliation(s)
- M Lämmerhofer
- Institute of Analytical Chemistry, University of Vienna, Austria.
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29
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Abstract
The separation factor of two compounds in chromatography is the ratio of their equilibrium constants or retention factors. This parameter is universally employed to investigate their resolution and to optimize the experimental conditions of their analysis. In enantioseparations, the situation is more complex because there is a mixed retention mechanism. The retention factor is the sum of two contributions, one enantioselective, the other nonselective. Although both contribute to retention, the latter being identical for the two enantiomers and does not contribute to their separation. We show how these two contributions can be measured and how it becomes necessary to distinguish between the apparent, alpha(app), and the true, alpha(true), separation factors. The existence of nonselective sites is responsible for alpha(app) being less than alpha(true). Depending on the difference between these two factors, the more effective approach to improve a separation is either to increase the enantioselectivity or to reduce the nonselective interactions. Practical applications to separations of different beta-blockers on cellobiohydrolase are discussed. The apparent enantioselectivity of alprenolol is larger and increases faster with increasing pH than that of the more hydrophobic propranolol, in spite of the importance of hydrophobic interactions in the enantioselective mechanism. These two unexpected properties are discussed and explained.
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Affiliation(s)
- G Götmar
- Department of Pharmacy, Uppsala, Sweden
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30
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Chapter 9 Recent developments in liquid chromatographic enantioseparation. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s1567-7192(00)80012-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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