Journal articles: 'Enantiomeric effect'

1

Tok, Kenan Can, Mehmet Gumustas, Giorgi Jibuti, Halit Sinan Suzen, Sibel A. Ozkan, and Bezhan Chankvetadze. "The Effect of Enantiomer Elution Order on the Determination of Minor Enantiomeric Impurity in Ketoprofen and Enantiomeric Purity Evaluation of Commercially Available Dexketoprofen Formulations." Molecules 25, no. 24 (December 11, 2020): 5865. http://dx.doi.org/10.3390/molecules25245865.

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In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w).

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2

Zhou, Juan, Qiao Chen, Li-lan Wang, Yong-hua Wang, and Ying-zi Fu. "Chiral Discrimination of Tryptophan Enantiomers via (1R, 2R)-2-Amino-1, 2-Diphenyl Ethanol Modified Interface." International Journal of Electrochemistry 2011 (2011): 1–6. http://dx.doi.org/10.4061/2011/502364.

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The paper reported that a simple chiral selective interface constructed by (1R, 2R)-2-amino-1, 2-diphenyl ethanol had been developed to discriminate tryptophan enantiomers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the characteristic analysis of the electrode. The results indicated that the interface showed stable and sensitive property to determine the tryptophan enantiomers. Moreover, it exhibited the better stereoselectivity for L-tryptophan than that for D-tryptophan. The discrimination characteristics of the chiral selective interface for discriminating tryptophan enantiomers, including the response time, the effect of tryptophan enantiomers concentration, and the stability, were investigated in detail. In addition, the chiral selective interface was used to determine the enantiomeric composition of L- and D-tryptophan enantiomer mixtures by measuring the relative change of the peak current as well as in pure enantiomeric solutions. These results suggested that the chiral selective interface has the potential for enantiomeric discrimination of tryptophan enantiomers.

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Gładkowski, Witold, Aleksandra Włoch, Aleksandra Pawlak, Angelika Sysak, Agata Białońska, Marcelina Mazur, Paweł Mituła, Gabriela Maciejewska, Bożena Obmińska-Mrukowicz, and Halina Kleszczyńska. "Preparation of Enantiomeric β-(2′,5′-Dimethylphenyl)Bromolactones, Their Antiproliferative Activity and Effect on Biological Membranes." Molecules 23, no. 11 (November 20, 2018): 3035. http://dx.doi.org/10.3390/molecules23113035.

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Three novel enantiomeric pairs of bromolactones possesing a 2,5-dimethylphenyl substituent at the β-position of the lactone ring have been synthesized from corresponding enantiomeric (E)-3-(2′,5′-dimethylphenyl)hex-4-enoic acids (4) by kinetically controlled bromolactonization with N-bromosuccinimide (NBS). γ-Bromo-δ-lactones (5) were isolated as the major products. Absolute configurations of stereogenic centers of γ-bromo-δ-lactones (5) were assigned based on X-ray analysis; configurations of cis δ-bromo-γ-lactones (6) and trans δ-bromo-γ-lactones (7) were determined based on mechanism of bromolactonization. Synthesized compounds exhibited significant antiproliferative activity towards the four canine cancer cell lines (D17, CLBL-1, CLB70, and GL-1) and one human cancer line (Jurkat). Classifying the compounds in terms of activity, the most active were enantiomers of trans δ-bromo-γ-lactones (7) followed by enantiomers of cis isomer (6) and enantiomeric γ-bromo-δ-lactones (5). Higher activity was observed for all stereoisomers with S configuration at C-4 in comparison with their enantiomers with 4R configuration. Synthesized compounds did not induce hemolysis of erythrocytes. The results of the interaction of bromolactones with red blood cell membranes suggest that these compounds incorporate into biological membranes, concentrating mainly in the hydrophilic part of the bilayer but have practically no influence on fluidity in the hydrophobic region. The differences in interactions with the membrane between particular enantiomers were observed only for γ-lactones: stronger interactions were found for enantiomer 4R,5R,6S of cis γ-lactone (6) and for enantiomer 4S,5R,6S of trans γ-lactone (7).

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4

Nathan, I., G. Agam, R. Mechoulam, A. Dvilansky, and A. A. Livne. "Effect of synthetic enantiomeric cannabinoids on platelet aggregation." Canadian Journal of Physiology and Pharmacology 70, no. 10 (October 1, 1992): 1305–8. http://dx.doi.org/10.1139/y92-182.

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The effect of a synthetic pair of enantiomeric cannabinoids on platelet function was evaluated. The nonpsychotropic enantiomer, the 1,1-dimethylheptyl homolog of (+)-(3S,4S)-7-hydroxy-Δ-6-tetrahydrocannabinol (HU-211), was found to be more active in inhibiting ADP-induced platelet aggregation than the highly psychotropic (−)-enantiomer (HU-210). The related (+)-(3R,4R) cannabinoid, HU-213, which lacks the 7-hydroxy moiety, exerted its inhibitory effect within a wider range of concentrations. The results indicate a differentiation between psychotropic activity and inhibition of platelet aggregation in the cannabinoid group of compounds.Key words: enantiomeric cannabinoids, platelet aggregation.

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5

Cook, J. I., S. Majeed, R. Ignell, J. A. Pickett, M. A. Birkett, and J. G. Logan. "Enantiomeric selectivity in behavioural and electrophysiological responses of Aedes aegypti and Culex quinquefasciatus mosquitoes." Bulletin of Entomological Research 101, no. 5 (May 18, 2011): 541–50. http://dx.doi.org/10.1017/s0007485311000162.

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Abstract1-Octen-3-ol is a kairomone for many haematophagous insects including mosquitoes. Numerous studies have examined the effects of racemic 1-octen-3-ol; however, few studies have investigated the role of individual enantiomers in relation to mosquito attraction. In the present study, we investigated the behavioural and electrophysiological responses of two mosquito species, Aedes aegypti and Culex quinquefasciatus, to individual enantiomers and mixtures of 1-octen-3-ol, employing a laboratory Y-tube olfactometer and single sensillum recordings. The olfactory receptor neurons of both Ae. aegypti and Cx. quinquefasciatus had a significantly higher response to the (R)-1-octen-3-ol enantiomer compared to the (S)-1-octen-3-ol enantiomer at 10−9 g μl−1 to 10−6 g μl−1. Behaviourally, Ae. aegypti was more responsive to the (R)-1-octen-3-ol enantiomer, showing an increase in flight activity and relative attraction compared to Cx. quinquefasciatus. The (R)-1-octen-3-ol enantiomer caused an increase in activation for Cx. quinquefasciatus. However, the most notable effect was from an (R:S)-1-octen-3-ol mixture (84:16) that caused significantly more mosquitoes to sustain their flight and reach the capture chambers (demonstrated by a reduced non-sustained flight activity), suggesting that it may have a behaviourally excitatory effect. For Cx. quinquefasciatus, a reduced relative attraction response was also observed for all treatments containing the (R)-1-octen-3-ol enantiomer, either on its own or as part of a mixture, but not with the (S)-1-octen-3-ol enantiomer. This is the first time enantiomeric selectivity has been shown for Ae. aegypti using electrophysiology in vivo. The implications of these results for exploitation in mosquito traps are discussed.

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6

Pálovics, Emese, Dorottya Fruzsina Bánhegyi, and Elemér Fogassy. "Effect of the Enantiomeric Ratio of Eutectics on the Results and Products of the Reactions Proceeding with the Participation of Enantiomers and Enantiomeric Mixtures." Chemistry 2, no. 3 (September 21, 2020): 787–95. http://dx.doi.org/10.3390/chemistry2030051.

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This perspective is focused on the main parameters determining the results of crystallization of enantiomers or enantiomeric mixtures. It was shown that the ratio of supramolecular and helical associations depends on the eutectic composition of the corresponding enantiomeric mixture. The M and P ratios together with the self-disproportionation (SDE) of enantiomers define the reaction of the racemic compound with the resolving agent. Eventually, each chiral molecule reacts with at least two conformers with different degrees of M and P helicity. The combined effect of the configuration, charge distribution, constituent atoms, bonds, flexibility, and asymmetry of the molecules influencing their behavior was also summarized.

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7

Salom, S. M., R. F. Billings, W. W. Upton, M. J. Dalusky, D. M. Grosman, T. L. Payne, C. W. Berisford, and T. N. Shaver. "Effect of verbenone enantiomers and racemic endo-brevicomin on response of Dendroctonusfrontalis (Coleoptera: Scolytidae) to attractant-baited traps." Canadian Journal of Forest Research 22, no. 7 (July 1, 1992): 925–31. http://dx.doi.org/10.1139/x92-123.

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Different enantiomeric ratios and elution rates of the inhibitor pheromones verbenone and racemic endo-brevicomin were evaluated for their effects on the numerical response of the southern pine beetle, Dendroctonusfrontalis Zimm., to attractant-baited traps. Enantiomeric ratios and elution rates of verbenone were important factors in inhibiting response of male D. frontalis. Deterrence was most effective for enantiomeric ratios of verbenone containing 34 and 50% of the (+) enantiomer. Using a 34% (+): 66% (−) mixture of verbenone, the number of male D. frontalis captured in attractant-baited traps declined as elution rates increased from 4.2 to 12.5 mg/h. None of the enantiomeric ratios or elution rates of verbenone tested consistently influenced female response. endo-Brevicomin added to attractant-baited traps reduced catches of male D. frontalis, but did not significantly reduce catches further when added to traps also emitting verbenone. Female catches were not reduced significantly by the presence of endo-brevicomin. Numerical responses of the predatory beetle Thanasimusdubius Fab. are generally unaffected by the presence of verbenone alone or in combination with endo-brevicomin.

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8

Bai, Hui. "Research progress of chiral ligand exchange stationary phases in the enantiomer resolution." E3S Web of Conferences 271 (2021): 04020. http://dx.doi.org/10.1051/e3sconf/202127104020.

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The structure of chiral drugs contains at least one asymmetric center. When the enantiomers act on the human body, they are recognized by chiral receptors and enzymes in vivo, which will show different physiological effects and even adverse reactions. Therefore, it is very important for the development of chiral pharmacy to obtain chiral enantiomers with a single configuration by racemic resolution. Some general impurities will be introduced in the production of chiral drugs, thus the detection of impurities is also a crucial step in the quality control of chiral medicines. The chiral ligand exchange stationary phase has a strong recognition effect on enantiomer analytes with multiple chelating sites, and is very suitable for the separation and control of biological samples such as amino acids. In this work, the development of chiral ligand exchange stationary phases in enantiomeric resolution is reviewed, which is expected to provide a basis for the quality control of complex chiral drug components.

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9

Rajin, Mariani, Asiah Binti Zulkifli, Sariah Abang, S. M. Anissuzzaman, and Azlina Harun Kamaruddin. "Effect of Reaction Parameters on the Lipase-Catalyzed Kinetic Resolution of (RS )-Metoprolol." ASEAN Journal of Chemical Engineering 20, no. 1 (June 29, 2020): 20. http://dx.doi.org/10.22146/ajche.51857.

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Racemic metoprolol is a selective ß1-blocker, which is used in cardiovascular disease treatment. It has been found that (S)-metoprolol has a higher affinity to bind the ß-adrenergic receptor compared to (R)-metoprolol. Moreover, the regulatory authorities’ high market demand and guidelines have increased the preference for single enantiomer drugs. In this work, the lipase-catalyzed kinetic resolution of racemic metoprolol was performed to obtain the desired enantiomer. The type of lipase, acyl donor, and solvent were screened out. This was achieved by Candida antarctica B lipase-catalyzed transesterification of racemic metoprolol in hexane and vinyl acetate as the solvent and an acyl donor, which gave maximum conversion of (S)-metoprolol (XS) of 52%, enantiomeric excess of substrate, (ees) of 92% and product (eeP) of 90% with enantiomeric ratio (E) of 62. This method can be considered as green chemistry, which can be applied to produce other enantiopure beta-blockers.

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10

Gambassi, G., M. C. Capogrossi, M. Klockow, and E. G. Lakatta. "Enantiomeric dissection of the effects of the inotropic agent, EMD 53998, in single cardiac myocytes." American Journal of Physiology-Heart and Circulatory Physiology 264, no. 3 (March 1, 1993): H728—H738. http://dx.doi.org/10.1152/ajpheart.1993.264.3.h728.

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The effects of the thiadiazinone derivative, 5-[1-(3,4-dimethoxybenzoyl)-1,2,3,4-tetrahydrochinolin-6-yl]-6-met hyl-3,6- dihydro-2H-1,3,4-thiadiazin-2-on (EMD 53998), and of its (+)EMD 57033 and (-)EMD 57439 enantiomers, were tested on the contractile properties and cytosolic [Ca2+] ([Ca2+]i) transients of single intact guinea pig cardiac myocytes. Cells were loaded with the ester form of the fluorescent probe, indo-1, and bathed in a N-2-hydroxyethyl-piperazine-N'-2-ethanesulfonic acid-buffered solution at 25 degrees C (1 mM of CaCl2, 1 Hz stimulation rate). All three substances exerted a pronounced increase in twitch amplitude: the maximal effect of the racemate (380% of control value) was approximately the sum of the effects of its two enantiomers (186 and 236% of control value for the (+)- and (-)-enantiomer, respectively). The [Ca2+]i transient, measured as the 410-to-490 nm indo-1 fluorescence ratio transient after excitation, was increased by the racemate and its (-)-enantiomer (172 and 152% of control value, respectively), but was not increased by the (+)-enantiomer. The racemate and the (-)-enantiomer, but not the (+)-enantiomer, markedly reduced the contraction duration and [Ca2+]i transient duration. In unstimulated cells resting length was significantly reduced by the (+)-enantiomer, and this was accompanied by a decrease in indo-1 fluorescence; the (-)-enantiomer had no effect on either parameter. In the presence of 2,3 butanedione monoxime (BDM), which markedly reduces twitch amplitude by inhibiting cross-bridge mechanics, addition of the (+)-enantiomer restored the twitch contraction to above the pre-BDM level without augmenting the [Ca2+]i transient. In contrast, the (-)-enantiomer failed to reverse the BDM-induced contractile depression, even though it caused a significant increase of the [Ca2+]i transient. Thus, in intact cells the positive inotropic effect of EMD 53998 is due to specific properties of its enantiomers: the (-)-enantiomer has adenosine 3',5'-cyclic monophosphate-like effects (increase in amplitude and reduction of [Ca2+]i transient and contraction durations), whereas the (+)-enantiomer enhances the myofilament-Ca2+ interaction.

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11

Bonifacino, Tiziana, Laura Micheli, Carola Torazza, Carla Ghelardini, Carlo Farina, Giambattista Bonanno, Marco Milanese, Lorenzo Di Cesare Mannelli, and Michael W. Scherz. "Pharmacological Profile of MP-101, a Novel Non-racemic Mixture of R- and S-dimiracetam with Increased Potency in Rat Models of Cognition, Depression and Neuropathic Pain." Cells 11, no. 24 (December 13, 2022): 4027. http://dx.doi.org/10.3390/cells11244027.

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The racemic mixture dimiracetam negatively modulates NMDA-induced glutamate release in rat spinal cord synaptosomal preparations and is orally effective in models of neuropathic pain. In this study, we compared the effects of dimiracetam, its R- or S-enantiomers, and the R:S 3:1 non-racemic mixture (MP-101). In vitro, dimiracetam was more potent than its R- or S-enantiomers in reducing the NMDA-induced [3H]D-aspartate release in rat spinal cord synaptosomes. Similarly, acute oral administration of dimiracetam was more effective than a single enantiomer in the sodium monoiodoacetate (MIA) paradigm of painful osteoarthritis. Then, we compared the in vitro effects of a broad range of non-racemic enantiomeric mixtures on the NMDA-induced [3H]D-aspartate release. Dimiracetam was a more potent blocker than each isolated enantiomer but the R:S 3:1 non-racemic mixture (MP-101) was even more potent than dimiracetam, with an IC50 in the picomolar range. In the chronic oxaliplatin-induced neuropathic pain model, MP-101 showed a significantly improved anti-neuropathic profile, and its effect continued one week after treatment suspension. MP-101 also performed better than dimiracetam in animal models of cognition and depression. Based on the benign safety and tolerability profile previously observed with racemic dimiracetam, MP-101 appears to be a novel, promising clinical candidate for the prevention and treatment of several neuropathic and neurological disorders.

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12

Long, Solida, Diana I. S. P. Resende, Anake Kijjoa, Artur M. S. Silva, André Pina, Tamara Fernández-Marcelo, M. Helena Vasconcelos, Emília Sousa, and Madalena M. M. Pinto. "Antitumor Activity of Quinazolinone Alkaloids Inspired by Marine Natural Products." Marine Drugs 16, no. 8 (July 31, 2018): 261. http://dx.doi.org/10.3390/md16080261.

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Many fungal quinazolinone metabolites, which contain the methyl-indole pyrazino [1,2-b]quinazoline-3,6-dione core, have been found to possess promising antitumor activity. The purpose of this work was to synthesize the enantiomeric pairs of two members of this quinazolinone family, to explore their potential as antitumor and their ability to revert multidrug resistance. The marine natural product fiscalin B (4c), and antienantiomers (4b, 5b, and 5c) were synthesized via a one-pot approach, while the syn enantiomers (4a, 4d, 5a, and 5d) were synthetized by a multi-step procedure. These strategies used anthranilic acid (i), chiral N-protected α-amino acids (ii), and tryptophan methyl esters (iii) to form the core ring of pyrazino[2,1-b]quinazoline-3,6-dione scaffold. Four enantiomeric pairs, with different enantiomeric purities, were obtained with overall yields ranging from 7 to 40%. Compounds 4a–d and 5a–d were evaluated for their growth inhibitory effect against two tumor cell lines. Differences between enantiomeric pairs were noted and 5a–d displayed GI50 values ranging from 31 to 52 μM, which are lower than those of 4a–d. Nevertheless, no effect on P-glycoprotein (P-gp) modulation was observed for all compounds. This study disclosed new data for fiscalin B (4c), as well as for its analogues for a future development of novel anticancer drug leads.

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13

Gammacurta, Marine, Sophie Tempere, Stéphanie Marchand, Virginie Moine, and Gilles De Revel. "Ethyl 2-hydroxy-3-methylbutanoate enantiomers: quantitation and sensory evaluation in wine." OENO One 52, no. 1 (March 20, 2018): 57–65. http://dx.doi.org/10.20870/oeno-one.2018.52.1.1902.

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Aim: To investigate chemical and sensory characteristics of ethyl 2-hydroxy-3-methylbutanoate in wines.Methods and results: Ethyl 2-hydroxy-3-methylbutanoate has been recently identified as a potential marker of lactic acid bacteria esterase activity. Enantiomers of this fruity ester were quantitated in 99 wines from various vintages and French regions using chiral gas chromatography (γ-cyclodextrin phase). Analyses revealed the predominant presence of the R enantiomer in red and white wines, with a maximum R/S enantiomeric ratio of 94/6 in a 1993 red wine. Results also highlighted greater levels of the ester in red than white wines, depending on grape origin. The detection thresholds of the R- and S-form were estimated at 4 µg/L and 1.5 µg/L in water and 51 mg/L and 21 mg/L in red wine, respectively. Moreover, ranking tests made with levels found in wines did not show significant sensory differences.Conclusion: The concentrations found in wines were considerably below the detection threshold, indicating no direct effect of these compounds on fruity aroma modulation. The absence of significant difference in sensory tests demonstrates that ethyl 2-hydroxy-3-methylbutanoate does not contribute significantly to the fruity aroma of red wine.Significance and impact of the study: To our knowledge, no previous research had determined the enantiomeric distribution and the sensory characteristics of this compound in wine.

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14

Hroboňová, Katarína, Zuzana Deáková, Jakub Moravčík, Jozef Lehotay, Daniel W. Armstrong, and Anna Lomenová. "Separation Of Methionine Enantiomers By Using Teicoplanin And Cyclofructan Columns." Nova Biotechnologica et Chimica 14, no. 1 (June 1, 2015): 1–11. http://dx.doi.org/10.1515/nbec-2015-0009.

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Abstract Methionine is a naturally occurring amino acid. Its enantiomeric separation by using high performance liquid chromatography on various types of chiral stationary phases was studied. The effect of mobile phase composition on enantioselectivity and retention was considered. The separation of the enantiomers was attained in different separation modes – reversed phase mode for the macrocyclic antibiotic chiral stationary phases (teicoplanin, teicoplanin aglycone), normal phase and polar organic phase modes for the isopropyl carbamate cyclofructan 6 chiral stationary phase. It was shown that the hydrogen bonding, dipole interactions, steric effects between methionine molecules and stationary phases play an important role in the separation of enantiomers.

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15

Chen, Senhua, Minghua Jiang, Bin Chen, Jintana Salaenoi, Shah-Iram Niaz, Jianguo He, and Lan Liu. "Penicamide A, A Unique N,N′-Ketal Quinazolinone Alkaloid from Ascidian-Derived Fungus Penicillium sp. 4829." Marine Drugs 17, no. 9 (September 5, 2019): 522. http://dx.doi.org/10.3390/md17090522.

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Previously unreported N,N′-ketal quinazolinone enantiomers [(−)-1 and (+)-1] and a new biogenetically related compound (2), along with six known compounds, 2-pyrovoylaminobenzamide (3), N-(2-hydroxypropanoyl)-2 amino benzoic acid amide (4), pseurotin A (5), niacinamide (6), citreohybridonol (7), citreohybridone C (8) were isolated from the ascidian-derived fungus Penicillium sp. 4829 in wheat solid-substrate medium culture. Their structures were elucidated by a combination of spectroscopic analyses (1D and 2D NMR and Electron Circular Dichroism data) and X-ray crystallography. The enantiomeric pair of 1 is the first example of naturally occurring N,N′-ketal quinazolinone possessing a unique tetracyclic system having 4-quinazolinone fused with tetrahydroisoquinoline moiety. The enantiomeric mixtures of 1 displayed an inhibitory effect on NO production in lipopolysaccharide-activated RAW264.7 cells, while the optically pure (–)-1 showed better inhibitory effect than (+)-1.

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Bock, William, and Enrique Peacock-López. "Chiral Oscillations and Spontaneous Mirror Symmetry Breaking in a Simple Polymerization Model." Symmetry 12, no. 9 (August 20, 2020): 1388. http://dx.doi.org/10.3390/sym12091388.

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The origin of biological homochirality—defined as the preference of biological systems for only one enantiomer—has widespread implications in the study of chemical evolution and the origin of life. The activation—polymerization—epimerization—depolymerization (APED) model is a theoretical model originally proposed to describe chiral symmetry breaking in a simple dimerization system. It is known that the model produces chiral and chemical oscillations for certain system parameters, in particular, the preferential formation of heterochiral polymers. In order to investigate the effect of higher oligomers, our model adds trimers, tetramers, and pentamers. We report sustained oscillations of all chemical species and the enantiomeric excess for a wide range of parameter sets as well as the periodic chiral amplification of a small initial enantiomeric excess to a nearly homochiral state.

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Słoczyńska, Karolina, Paulina Koczurkiewicz, Kamil Piska, Beata Powroźnik, Katarzyna Wójcik-Pszczoła, Katarzyna Klaś, Magdalena Wyszkowska-Kolatko, and Elżbieta Pękala. "Similar Safety Profile of the Enantiomeric N-Aminoalkyl Derivatives of Trans-2-Aminocyclohexan-1-ol Demonstrating Anticonvulsant Activity." Molecules 24, no. 13 (July 9, 2019): 2505. http://dx.doi.org/10.3390/molecules24132505.

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Epilepsy is one of the most common neurological disorder in the world. Many antiepileptic drugs cause multiple adverse effects. Moreover, multidrug resistance is a serious problem in epilepsy treatment. In the present study we evaluated the safety profile of three (1–3) new chiral N-aminoalkyl derivatives of trans-2-aminocyclohexan-1-ol demonstrating anticonvulsant activity. Our aim was also to determine differences between the enantiomeric compounds with respect to their safety profile. The results of the study indicated that compounds 1–3 are non-cytotoxic for astrocytes, although they exhibit cytotoxic activity against human glioblastoma cells. Moreover, 1–3 did not affect the viability of HepG2 cells and did not produce adducts with glutathione. Compounds 1–3 demonstrated no mutagenic activity either in the Salmonella typhimurium or in Vibrio harveyi tests. Additionally, the compounds displayed a strong or moderate antimutagenic effect. Finally, the P-glycoprotein (P-gp) ATPase assay demonstrated that both enantiomers are potent P-gp inhibitors. To sum up, our results indicate that the newly synthesized derivatives may be considered promising candidates for further research on anticonvulsant drug discovery and development. Our study indicated the similar safety profile of the enantiomeric N-aminoalkyl derivatives of trans-2-aminocyclohexan-1-ol, although in the previous studies both enantiomers differ in their biotransformation pathways and pharmacological activity.

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18

Blindheim, Fredrik, Mari Hansen, Sigvart Evjen, Wei Zhu, and Elisabeth Jacobsen. "Chemoenzymatic Synthesis of Synthes as Precursors for Enantiopure Clenbuterol and Other β2 Agonists." Catalysts 8, no. 11 (November 4, 2018): 516. http://dx.doi.org/10.3390/catal8110516.

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Clenbuterol is a β2-agonist used in the veterinary treatment of asthma in several countries. The drug is listed on the World Antidoping Agency’s prohibited list due to its effect on increased protein synthesis in the body. However, racemic clenbuterol has recently been shown to reduce the risk of Parkinson’s disease. In order to reveal which one (or both) of the enantiomers that cause this effect, pure enantiomers need to be separately studied. (R)-1-(4-Amino-3,5-dichlorophenyl)-2-bromoethan-1-ol has been synthesised in 93% enantiomeric excess (ee) by asymmetric reduction of the corresponding ketone catalysed by a ketoreductase and nicotinamide adenine dinucleotide phosphate (NADPH) as the cofactor in dimethyl sulfoxide (DMSO). (S)-N-(2,6-Dichloro-4-(1-hydroxyethyl)phenyl)acetamide has been synthesised in >98% ee by the same system. Both synthons are potential precursors for clenbuterol enantiomers.

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Mengya Liao, Mengya Liao, Xin Wang Xin Wang, and Qin Wang and Yiwen Zhang Qin Wang and Yiwen Zhang. "Direct Enantioseparation of Lorlatinib Enantiomers by Liquid Chromatography on a Chiralpak IB Column." Journal of the chemical society of pakistan 45, no. 1 (2023): 53. http://dx.doi.org/10.52568/001195/jcsp/45.01.2023.

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Enantiomeric forms of many drugs are known to have different physiological and therapeutic effects. Previous studies indicated that the inhibitory activity of an enantiomer of Lorlatinib on L1196M kinase was 300 times lower than that of Lorlatinib. In this study, an analytical method for the enantioseparation of Lorlatinib was established on a Chiralpak IB column. Baseline separation was obtained within 10 min using v(n-hexane): v(2-propanol): v(diethylamine) = 85:15:0.1 as mobile phase, and a resolution higher than 2.2. Various factors of HPLC such as the effect of chiral columns, the contents of mobile phase and column temperature were thoroughly investigated. Calibration curves were plotted within the concentration range between 10 and 1000 μg mL-1 (n = 8), and recoveries between 97.86% and 100.99% were obtained, with a relative standard deviation (RSD) lower than 1.6%. The LOD and LOQ for Lorlatinib were 10.34 and 34.49 μg mL-1, respectively, and those for its enantiomer were 11.76 and 39.21 μg mL-1, respectively. Validating factors such as the accuracy, precision, linear relationship, and LOD/LOQ confirmed that the method has the advantages of high efficiency, accuracy and stability and can be used to detect the enantiomeric purity of Lorlatinib. In addition, the chiral recognition mechanisms were discussed according to the thermodynamic parameters and simulation studies between racemates and CSPs.

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RUIZ del CASTILLO, M. L., G. FLORES, G. P. BLANCH, and M. HERRAIZ. "Effect of Thermal Treatment during Processing of Orange Juice on the Enantiomeric Distribution of Chiral Terpenes." Journal of Food Protection 67, no. 6 (June 1, 2004): 1214–19. http://dx.doi.org/10.4315/0362-028x-67.6.1214.

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Chiral terpenes in orange juices were examined by solid-phase microextraction–gas chromatography-mass spectrometry to study the dependence of their enantiomeric composition on the thermal treatment applied during the industrial manufacture. The experimental conditions used in the isolation and concentration of the compounds of interest produced relative standard deviations ranging from 2.9 to 15.1% when absolute areas were used and from 1.7 to 18.3% when normalized areas were used. Recovery varied between 8.8 and 56.1%, and detection limits ranged from 0.11 to 0.32 μg/ml. The enantiomeric compositions of the majority of the chiral terpenes varied within a reasonably narrow range. Nevertheless, the enantiomeric ratio of two monoterpene alcohols, α-terpineol and linalool, exhibited considerable variation according to the thermal treatment used in the manufacture of the juices. Therefore, the knowledge of the enantiomeric composition of α-terpineol and linalool might be useful for thermal treatment control purposes.

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Salinas, Melissa, James Calva, Luis Cartuche, Eduardo Valarezo, and Chabaco Armijos. "Chemical Composition, Enantiomeric Distribution and Anticholinesterase and Antioxidant Activity of the Essential Oil of Diplosthephium juniperinum." Plants 11, no. 9 (April 28, 2022): 1188. http://dx.doi.org/10.3390/plants11091188.

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The aim of this study was to extract and identify the chemical compounds of Diplosthephium juniperinum essential oil (EO) from Ecuador and to assess its anticholinesterase and antioxidant properties. The EO chemical composition was determined by GC–MS. A total of 74 constituents of EO were identified, representing 97.27% in DB-5ms and 96.06% in HP-INNOWax of the total EO. The major constituents (>4.50%) identified were: α-pinene (21.52, 22.04%), geranyl acetate (10.54, 7.78%), silphiper-fol-5-ene (8.67, 7.38%), α-copaene (8.26, 8.18%), 7-epi-silphiperfol-5-ene (4.93, 5.95%), and germacrene D (4.91, 6.00%). Enantioselective analysis of the volatile fraction of D. juniperinum showed: (+)-α-pinene as a pure enantiomer and 5 pairs of enantiomeric compounds. Among them, (−)-β-Pinene and (−)-Germacrene D presented a high enantiomeric excess of 93.23 and 84.62%, respectively, while (−)-α-Thujene, (−)-Sabinene and (S)-4-Terpineol with a lower enantiomeric excess of 56.34, 47.84 and 43.11%, respectively. A moderate inhibitory effect was observed for Acetylcholinesterase (AChE) and Butyrylcholinesterase (BuChE) enzymes with IC50 values of 67.20 ± 7.10 and 89.00 ± 9.90 µg/mL, respectively. A lower antioxidant potential was observed for the EO measured through DPPH and ABTS radical scavenging assays with SC50 values of 127.03 and >1000 µg/mL, respectively. To the best of our knowledge, this is the first report of the chemical composition, enantiomeric distribution and, anticholinesterase and antioxidant potential of the EO of D. juniperinum. As future perspective, further in-vivo studies could be conducted to confirm the anticholinesterase potential of the EO.

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Ali, Imran, Mohd Suhail, Leonind Asnin, and Hassan Y. Aboul-Enein. "Effect of Various Parameters and Mechanism of Reversal Order of Elution in Chiral HPLC." Current Analytical Chemistry 16, no. 1 (January 8, 2020): 59–78. http://dx.doi.org/10.2174/1573411015666190103145916.

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Background: Chiral separation involves many phenomena in which the elution order of the enantiomers has its unique position. The phenomenon of elution order of the enantiomers has also been used in the determination of optical purity which is favorable to elute the major component after minor enantiomeric impurity but the main problem is that, this phenomenon is rare. Results: This review rumors the reversal order of elution of many chiral molecules in HPLC. Besides, this review pronounces the effects of pH, derivatisation of drugs, the composition of the mobile phase, and temperature on the reversal order of elution of chiral drugs. The efforts are also made to discuss the possible future perspectives of reversal order of elution. Conclusion: Various parameters such as pH, mobile phase composition, temperature, and chemical structure of the analytes play a role in the phenomena of the reversal order of elution of many chiral molecules which are discussed in the article.

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23

Xu, Zifu, Jin Guan, Huili Shao, Shitong Fan, Xiaoyu Li, Shuang Shi, and Feng Yan. "Combined Use of Cu(II)-L-Histidine Complex and β-Cyclodextrin for the Enantioseparation of Three Amino Acids by CE and a Study of the Synergistic Effect." Journal of Chromatographic Science 58, no. 10 (August 31, 2020): 969–75. http://dx.doi.org/10.1093/chromsci/bmaa058.

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Abstract A new capillary electrophoresis method was applied to chiral separation of three amino acids, including D,L-tryptophan, D,L-tyrosine and D,L-phenylalanine. The chiral resolution was attained in an untreated fused-sillica capillary using a dual chiral selector, which was made up of Cu(II)-L-histidine complex and β-cyclodextrin (CD). The cardinal factors influencing its separation efficiency, such as chiral selectors, buffer pH and applied voltage, were optimized. Best results were acquired by using a buffer consisting of 10 mmol/L Cu(II), 13 mmol/L L-histidine, 8 mmol/L β-CD, 5 mmol/L phosphate adjusted to pH 5.0 and 15 kV applied voltage. All enantiomers were entirely resolved within 20 min with high resolutions of 3.6~6.1. The analysis method was verified through the determination of D,L-tryptophan in terms of linearity, precision and accuracy. And the robustness of this method was proved. The Limit of Detection and Limit of Quantification for both enantiomers were 2.5 and 5 μg/mL, respectively. The method was perfectly applied to the determination of the enantiomeric purity of L-tryptophan. Furthermore, the interaction between Cu(II)-L-histidine complex and β-CD was also studied using Ultraviolet-visible and 1H NMR spectroscopy to explain the synergistic effect involved. The results illustrated that Cu(II)-L-histidine complex and β-CD played a synergistic role in the enantiomeric separation of chiral drugs, with good prospects for application.

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Lunkley, Jamie, Ngoc Nguyen, Kristina Tuminaro, Dana Margittai, and Gilles Muller. "The Importance of Solvent Effects on the Mechanism of the Pfeiffer Effect." Inorganics 6, no. 3 (August 29, 2018): 87. http://dx.doi.org/10.3390/inorganics6030087.

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The Pfeiffer effect is observed when an optically active compound such as an amino acid is introduced to a solution containing a labile racemic metal complex, and an equilibrium shift is obtained. The “perturbation” results in an excess of one enantiomer over the other. The shift is a result of a preferential outer sphere interaction between the introduced chiral species and one enantiomeric form (Λ or ∆) of a labile metal complex. Speculations regarding the mechanism of the Pfeiffer effect have attributed observations to a singular factor such as pH, solvent polarity, or numerous other intermolecular interactions. Through the use of the lanthanide(III) complexes [Tb(DPA)3]3− and [Eu(DPA)3]3− (where DPA = 2,6-pyridinedicarboxylate) and the amino acids l-serine and l-proline; it is becoming clear that the mechanism is not so simply described as per the preliminary findings that are discussed in this study. It appears that the true mechanism is far more complicated than the attribute just a singular factor. This work attempts to shine light on the fact that understanding the behavior of the solvent environment may hypothetically be the key to offering a more detailed description of the mechanism.

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Polavarapu, Prasad L. "Optical purity, enantiomeric excess and the Horeau effect." Organic & Biomolecular Chemistry 18, no. 35 (2020): 6801–6. http://dx.doi.org/10.1039/d0ob01497d.

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Optical purity (op) and enantiomeric excess (ee) become equal when either heterochiral dimerization constant is twice that of homochiral dimerization constant or specific rotations of monomer and dimer are equal.

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Böttiger, D., N. G. Johansson, P. Lind, B. Lindborg, R. Noréen, P. Putkonen, L. Vrang, B. Wahren, and B. Öberg. "Inhibition of SIV and HIV-2 Replication in Cynomolgus Monkeys by (-)9-[4-Hydroxy-2-(Hydroxymethyl)-Butyl]Guanine (H2G)." Antiviral Chemistry and Chemotherapy 7, no. 1 (February 1996): 21–26. http://dx.doi.org/10.1177/095632029600700104.

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The antiherpes compound (-)9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) has been found to suppress the multiplication of SIVsm and HIV-2 in cynomolgus monkeys. This was seen as a delay in the appearance of viral antigen in serum during the primary infection at drug concentrations of 3×10 mg kg−1 day−1 and higher, when H2G was given subcutaneously. These effects of H2G on SIVsm and HIV-2 replication in monkeys were similar to those observed using the same dose of 3′-azidothymidine (AZT). A complete prevention of HIV-2 infection was observed in one of four animals treated with 3×10 mg kg−1 day−1 of H2G. The enantiomeric mixture (+)H2G at 3×25 mg kg−1 day−1 also delayed the appearance of SIVsm antigen but the (+)enantiomer of H2G at 3×10 mg kg−1 day−1 had no effect on primary SIVsm infection in monkeys, indicating that only the (−)enantiomer (H2G) was inhibitory and that this effect was not influenced by the presence of the (+)enantiomer. No adverse effects on blood chemistry or haematology were observed in monkeys given 25 mg kg−1 day−1 of H2G for 9 weeks or 3×25 mg kg−1 day−1 for 10 days.

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Fransson, Linda, Anna Laurell, Khalid Widyan, Erica Wingstrand, Karl Hult, and Christina Moberg. "Minor Enantiomer Recycling-Effect of Two Reinforcing Catalysts on Product Yield and Enantiomeric Excess." ChemCatChem 2, no. 6 (June 7, 2010): 683–93. http://dx.doi.org/10.1002/cctc.200900327.

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Wu, Xiuli, Yange Zhang, Wenzhen Li, Tingmei Liu, Yu Yang, Yijie Wang, and Yiwen Zhang. "A Validated LC Method for the Enantiomeric Separation of EAI045 on Chiral Stationary Phase." Journal of Chromatographic Science 58, no. 6 (April 18, 2020): 562–68. http://dx.doi.org/10.1093/chromsci/bmz125.

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Abstract A simple and accurate chiral liquid chromatographic method was developed for enantiomeric resolution and determination of 2-(5-fluoro-2-hydroxyphenyl)-2-(1-oxo-2,3-dihydro-1H-isoindol-2-yl)-N-(1,3-thiazol-2-yl)acetamide (EAI045). The enantiomers of EAI045 were baseline resolved on a Chiralpak AD-H (250 mm × 4.6 mm, 5 μm) column using a mobile phase system containing n-hexane: 2-propanol (75: 25 v/v) at a flow rate of 1 mL min−1 at 30°C. The eluted analytes were subsequently detected with an ultraviolet detector at 254 nm. The effects of organic modifiers and temperature on the enantioselectivity and resolution of the enantiomers were evaluated. The calibration curves were plotted within the concentration range between 2 and 600 μg mL−1 (n = 11), and recoveries between 98.74% and 101.52% were obtained, with relative standard deviation < 1.4%. The limit of detection and limit of quantitation for R-enantiomer were 0.94 and 3.07 μg mL−1 and for S-enantiomer were 0.86 and 2.84 μg mL−1, respectively. The validated method was found to be suitable for enantiomeric separation and sufficiently accurate for the determination of enantiomeric purity of EAI045 in bulk drugs.

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Costa, Ana Rita, Virgínia M. F. Gonçalves, Bruno B. Castro, João Soares Carrola, Ivan Langa, Ariana Pereira, Ana Rita Carvalho, Maria Elizabeth Tiritan, and Cláudia Ribeiro. "Toxicity of the 3,4-Methylenedioxymethamphetamine and Its Enantiomers to Daphnia magna after Isolation by Semipreparative Chromatography." Molecules 28, no. 3 (February 2, 2023): 1457. http://dx.doi.org/10.3390/molecules28031457.

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MDMA (3,4-methylenedioxymethamphetamine) is a chiral psychoactive recreational drug sold in illicit markets as racemate. Studies on the impact of MDMA on aquatic organisms are scarce. While enantioselectivity in toxicity in animals and humans has been reported, none is reported on aquatic organisms. This study aimed to investigate the ecotoxicological effects of MDMA and its enantiomers in Daphnia magna. For that, enantiomers (enantiomeric purity > 97%) were separated by liquid chromatography using a homemade semipreparative chiral column. Daphnids were exposed to three concentrations of (R,S)-MDMA (0.1, 1.0 and 10.0 µg L−1) and two concentrations of (R)- and (S)-enantiomers (0.1 and 1.0 µg L−1) over the course of 8 days. Morphophysiological responses were dependent on the substance form and daphnia development stage, and they were overall not affected by the (R)-enantiomer. Changes in swimming behaviour were observed for both the racemate and its enantiomers, but enantioselective effects were not observed. Reproductive or biochemical changes were not observed for enantiomers whereas a significant decrease in acetylcholinesterase and catalase activity was noted at the highest concentration of (R,S)-MDMA (10 µg L−1). Overall, this study showed that sub-chronic exposure to MDMA racemate and its enantiomers can interfere with morphophysiological and swimming behaviour of D. magna. In general, the (R)-enantiomer demonstrated less toxicity than the (S)-enantiomer.

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Cabral, Marisol, Raquel Martín-Venegas, and Juan José Moreno. "Differential cell growth/apoptosis behavior of 13-hydroxyoctadecadienoic acid enantiomers in a colorectal cancer cell line." American Journal of Physiology-Gastrointestinal and Liver Physiology 307, no. 6 (September 15, 2014): G664—G671. http://dx.doi.org/10.1152/ajpgi.00064.2014.

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Cyclooxygenases (COXs) and lipoxygenases (LOXs) are important enzymes that metabolize arachidonic and linoleic acids. Various metabolites generated by the arachidonic acid cascade regulate cell proliferation, apoptosis, differentiation, and senescence. Hydroxyoctadecadienoic acids (HODEs) are synthesized from linoleic acid, giving two enantiomeric forms for each metabolite. The aim was to investigate the effect of 13-HODE enantiomers on nondifferentiated Caco-2 cell growth/apoptosis. Our results indicate that 13(S)-HODE decreases cell growth and DNA synthesis of nondifferentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS). Moreover, 13(S)-HODE showed an apoptotic effect that was reduced in the presence of a specific peroxisome proliferator-activated receptor-γ (PPARγ) antagonist. In addition, we observed that 13(S)-HODE but not 13(R)-HODE is a ligand to PPARγ, confirming the implication of this nuclear receptor in 13(S)-HODE actions. In contrast, 13(R)-HODE increases cell growth and DNA synthesis in the absence of FBS. 13(R)-HODE interaction with BLT receptors activates ERK and CREB signaling pathways, as well as PGE2 synthesis. These results suggest that the proliferative effect of 13(R)-HODE could be due, at least in part, to COX pathway activation. Thus both enantiomers use different receptors and have contrary effects. We also found these differential effects of 9-HODE enantiomers on cell growth/apoptosis. Therefore, the balance between (R)-HODEs and (S)-HODEs in the intestinal epithelium could be important to its cell growth/apoptosis homeostasis.

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Teng, Fei, Jianbo Ji, Yue Yang, and Haina Wang. "A useful quantitative model for determining the optical purity of praziquantel enantiomers based on near infrared spectroscopy with partial least squares." Journal of Near Infrared Spectroscopy 30, no. 5 (October 2022): 246–53. http://dx.doi.org/10.1177/09670335221130428.

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In this study, a new method was developed for the determination of praziquantel (PZQ) enantiomers in solution. Praziquantel, as a highly effective and low-toxic broad-spectrum antiparasitic drug developed in the 1970s, is the first choice for the etiology of schistosomiasis treatment recommended by the World Health Organization. It is by far the most effective anti-schistosomiasis drug. PZQ is a chiral drug with a chiral carbon atom and two enantiomers, of which R-PZQ is the main contributor of the anti-schistosome effect. The quantitative model was established based on near infrared (NIR) spectroscopy combined with the partial least square (PLS) method. Using sucrose as a chiral selector, the collected spectral information was processed by the second derivative and Savitzky-Golay smoothing filter, and comprehensively analyzed in the two bands of 1816.9–1884.3 nm and 1405.3–1425.4 nm to establish a good PLS regression model. Internal cross-validation of the model was carried out. In principle, the enantiomeric excess could be determined as low as 1.33%. The mole fraction of S-PZQ determined by HPLC was used as a reference method, and three batches of samples from the same manufacturer were used for independent external validation with an error of ± 4%. The results showed that this quantitative model could be used to determine the enantiomer content of the chiral drug PZQ. It realized the rapid and sensitive analysis of PZQ tablets and provided a new strategy for the quality analysis of chiral drugs.

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Antonsen, Simen, Erling B. Monsen, Kirill Ovchinnikov, Jens M. J. Nolsøe, Dag Ekeberg, Jette E. Kristiansen, Dzung B. Diep, and Yngve Stenstrøm. "Synthesis of the Enantiomers of Thioridazine." SynOpen 04, no. 01 (January 2020): 12–16. http://dx.doi.org/10.1055/s-0039-1690834.

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Thioridazine, a well-known antipsychotic drug, has shown promising effects on several bacterial strains (including Mycobacterium tuberculosis and methicillin-resistant Staphylococcus aureus). Suppressive effects towards selected cancer cell-lines have also been reported. However, due to adverse effects, the compound is no longer in use for the primary indication. More recent research has demonstrated that these side effects are limited to one of the two enantiomers, (+)-thioridazine. The question arises to whether the beneficial effects of thioridazine are limited to one enantiomer, or if (–)-thioridazine can prove itself to be useful in its pure enantiomeric state. The published procedures on the synthesis of the optically pure enantiomers of thioridazine were found to be unsatisfactory, either due to low optical purity, high cost, or problems scaling up. Herein, we have used an auxiliary-based strategy for the total synthesis of both enantiomers in high optical purity and good overall yield. The strategy can easily be scaled up. Both enantiomers were tested against several bacteria. Comparison of the racemic mixture, (–)-thioridazine and its (+)-antipode revealed that they have the same antimicrobial effects. Thus, the non-toxic enantiomer, (–)-thioridazine, can prove useful in this role and should be investigated further.

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Rosetti, Alessia, Claudio Villani, Marco Pierini, and Roberto Cirilli. "Comparison of Coated and Immobilized Chiral Stationary Phases Based on Amylose tris-[(S)-α-Methylbenzylcarbamate] for the HPLC Enantiomer Separation of α-Lipoic Acid and Its Reduced Form." Molecules 26, no. 6 (March 20, 2021): 1747. http://dx.doi.org/10.3390/molecules26061747.

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The couple of chiral sulfur compounds α-lipoic acid (ALA)/α-dihydrolipoic acid (DHALA) has attracted considerable attention in recent years owing to its remarkable anti-inflammatory and antioxidant properties. It is well known that the chirality of the C6 plays a key role in determining the biological activity of ALA. The natural occurring (R)-ALA enantiomer is an essential cofactor for key oxidative metabolism enzyme complexes and, after oral administration of the racemic mixture, it shows higher plasma concentration than (S)-ALA. Differently, the in vivo enantioselective action difference between the enantiomers of DHALA has not yet been studied. This lacking is perhaps due to the unavailability of analytical methods capable of determining the enantiomeric composition of biological samples during pharmacokinetic and pharmacodynamic events. In the present work, the direct and baseline enantioresolution of both chiral acids by HPLC on two amylose-derived chiral stationary phases is presented. The proposed chiral enantioselective protocol, therefore, does not require pre- or on-column derivatization. The performance of the coated Chiralpak AS-H CSP and the new immobilized Chiralpak IH-3 CSP, which have the same chiral selector amylose tris-[(S)-α-methylbenzylcarbamate], were compared using conventional normal-phase mobile phases containing ethanol or 2-propanol as alcoholic solvents and a fixed percentage of trifluoroacetic acid. Nonconventional eluents containing dichloromethane, ethyl acetate, and 2-methyltetrahydrofuran as organic cosolvents were applied in the separation of the enantiomers of two carboxylic acids on the immobilized Chiralpak IH-3 CSP. The effect of the column temperature was carefully evaluated in order to improve enantioselectivity. Adequate amounts of enantiomers were isolated by an analytical-size Chiralpak IH-3 column and submitted to chiroptical measurements. The absolute configuration assignment of the isolated enantiomers was determined by a multidisciplinary procedure based on the comparison of the experimental and calculated chiroptical properties.

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Răsădean, Dora M., Samuel W. O. Harrison, Isobel R. Owens, Aucéanne Miramont, Frances M. Bromley, and G. Dan Pantoș. "Importance of Chiral Recognition in Designing Metal-Free Ligands for G-Quadruplex DNA." Molecules 24, no. 8 (April 15, 2019): 1473. http://dx.doi.org/10.3390/molecules24081473.

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Four pairs of amino acid-functionalized naphthalenediimide enantiomers (d- and l-lysine derived NDIs) were screened toward G-quadruplex forming sequences in telomeres (h-TELO) and oncogene promoters: c-KIT1, c-KIT2, k-RAS and BCL-2. This is the first study to address the effect of point chirality toward G-quadruplex DNA stabilization using purely small organic molecules. Enantioselective behavior toward the majority of ligands was observed, particularly in the case of parallel conformations of c-KIT2 and k-RAS. Additionally, Nε-Boc-l-Lys-NDI and Nε-Boc-d-Lys-NDI discriminate between quadruplexes with parallel and hybrid topologies, which has not previously been observed with enantiomeric ligands.

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Wadai, H., K. Yamaguchi, T. Kanno, T. Nakamura, Tomoji T., K. Hasagawa, H. Naiki, and Y. Goto. "Effect of Enantiomeric Fragment for Amyloid Fibril Formation." Seibutsu Butsuri 43, supplement (2003): S63. http://dx.doi.org/10.2142/biophys.43.s63_4.

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Merelli, Bérangère, Laurence Menguy, Estelle Soubeyrand-Lenoir, and Jean-Claude Cherton. "Determination of the enantiomeric composition of chiral delta-2-thiazolines-1,3 by1H and19F NMR spectroscopy using chiral solvating agents." Spectroscopy 20, no. 3 (2006): 95–107. http://dx.doi.org/10.1155/2006/698685.

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Studies of the perturbing effect of chiral solvating agents (CSAs) namely the fluoroalcohols5aand5bupon the NMR spectra of chiral Δ2-thiazolines1presenting interesting insecticidal properties demonstrated the ability of these CSAs to afford diastereomeric solvates from these substrates providing their enantiomeric discrimination. Thus, for five of the six tested Δ2-thiazolines1Aand1Bthere is at least one possibility to proceed to their enantiomeric discrimination either by1H or19F NMR using mostly5bas CSA.

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Karakka Kal, Abdul Khader, Tajudheen K. Karatt, Moses Philip, Samir Meissir, and Jahfar Nalakath. "Separation and Determination of the Enantiomeric Levamisole and Dexamisole in Equine Plasma Samples Using Chiral Polysaccharide Column/ LC-MS/MS." Current Analytical Chemistry 16, no. 6 (August 13, 2020): 761–67. http://dx.doi.org/10.2174/1573411015666190808103143.

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Background: Drug Enforcement Administration confirmed that many manufacturers began adding tetramisole or its individual isomers to cocaine as an adulterant, and believed that tetramisole may augment cocaine’s effects. In recent times, there is an increasing trend in the usage of tetramisole and its individual enantiomer in race sports especially in horse and camel races. So it’s is very much required to confirm the stereochemistry of this illicit drug in the routine race day samples coming to the anti-doping labs in order to avoid legal arguments and challenges to the analytical findings. Methods: The aim of the study was to develop a simple, rapid and accurate method for the chiral separation and determination of enantiomeric mixtures of levamisole and dexamisole using Thermo Q-Exactive High-Resolution Mass Spectrometer. In order to evaluate the suitability of the method for determining the enantiomeric purity of tetramisole, validation studies were also carried out by using equine plasma. Results: The enantio-separation was achieved using the Lux i-cellulose-5 column. Isocratic flow was used with a 1:1 mixture of mobile phase A (10 mM ammonium acetate in water) and mobile phase B (acetonitrile), at a flow rate of 0.6 mL/min. The run time was 8.0 min, and the column temperature was 50°C. Dexamisole eluted at 5.94 min, and levamisole eluted at 6.62 min, giving the R-value of 1.50. The obtained inter-day precisions of dexamisole, levamisole were 3.16% and 2.85%, respectively. The accuracy of dexamisole was in the range of 97.78 to 102.44%, and that for levamisole was 99.16 to 102.82%. The limit of quantification value for both isomers in this method was 0.1 ng/ mL. The method was linear in the range of 0 to 50 ng/mL. Conclusion: Chromatographic separation was achieved using the polysaccharide cellulose chiral column, and the reverse-phase separation approach was found to have the highest potential for successful chiral resolution in LC-MS. Linearity, precision, accuracy, detection limit, recovery, and the matrix effect in equine plasma were determined. Under the optimized conditions, the validated method can be applied for the identification and detection of the tetramisole enantiomers in different sources of illicit drugs of abuse.

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Ribeiro-Filho, Jaime, Juliana da Silva Brandi, Hermann Ferreira Costa, Karina Carla de Paula Medeiros, Jacqueline Alves Leite, Damião Pergentino de Sousa, and Márcia Regina Piuvezam. "Carvone Enantiomers Differentially Modulate IgE-Mediated Airway Inflammation in Mice." International Journal of Molecular Sciences 21, no. 23 (December 3, 2020): 9209. http://dx.doi.org/10.3390/ijms21239209.

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Carvone is a monoterpene found in nature in the form of enantiomers (S- and R-). While previous research has demonstrated the anti-inflammatory and anti-allergic effects of carvone, the influence of carvone enantiomeric composition on its anti-allergic activity remains to be investigated. This study aimed to evaluate the anti-allergic activity of carvone enantiomers in a murine model of airway allergic inflammation induced by sensitization and challenge with ovalbumin (OVA). The oral treatment with R-carvone or S-carvone 1 h before each challenge inhibited the number of leukocytes and eosinophils in the bronchoalveolar lavage (BAL). R-carvone inhibited leukocyte infiltration and mucus production in the lung, which was correlated with decreased production of OVA-specific IgE in the serum and increased concentrations of IL-10 in the BAL. On the other hand, the administration of S-carvone had little inhibitory effect on inflammatory infiltration and mucus production in the lung, which might be associated with increased production of IFN-γ in the BAL. When administered 1 h before each sensitization, both enantiomers inhibited eosinophil recruitment to the BAL but failed in decreasing the titers of IgE in the serum of allergic mice. Our data indicate that carvone enantiomers differentially modulated IgE-mediated airway inflammation in mice. In conclusion, unlike S-carvone, R-carvone has the potential to be used in anti-allergic drug development.

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Gandhi, Karan, Umang Shah, and Sandip Patel. "Drug Stereochemistry: A Prodigy For Pharmacology and Drug Development." Current Drug Discovery Technologies 17, no. 5 (December 23, 2020): 565–73. http://dx.doi.org/10.2174/1570163816666190502101803.

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Stereochemistry has evinced the importance of many chiral drugs with respect to drug designing and development. A literature review was conducted for several chiral drugs involving pharmacokinetic and pharmacodynamic parameters of their enantiomers along with their uses in certain diseased conditions. This article mainly includes the pharmacological profile review of some chiral drugs and the aspects due to which the single enantiomer is of importance as compared to the racemic mixture of the drug. This was achieved by moderating the side effects or toxic effects; or by the potentiated activity of the single enantiomer. Resolution deals with the separation of racemic compounds which shows up the credibility to obtain the desired enantiomeric properties. As isomers vary in their pharmacokinetic and pharmacodynamic profiles, chiral drugs have showcased considerable importance in the drug development process. Both the enantiomers have a different pharmacological profile in the treatment of a disease, which differentiates them from drug racemates.

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Chałupka, Joanna, Adam Sikora, Aleksandra Kozicka, and Michał Piotr Marszałł. "Overview: Enzyme-catalyzed Enantioselective Biotransformation of Chiral Active Compounds Used in Hypertension Treatment." Current Organic Chemistry 24, no. 23 (December 28, 2020): 2782–91. http://dx.doi.org/10.2174/1385272824999201020204256.

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Enzymatic kinetic resolution is one of the methods which allows for the synthesis of enantiomerically pure various active pharmaceutical ingredients. In contrast to chemical routes, enzymatic reactions have characteristics, including mild reaction conditions, a few byproducts, and relatively high activity of the used enzymes. β-adrenolytic drugs are widely used in the treatment of hypertension and cardiovascular disorders. Due to the fact that β- blockers possess an asymmetric carbon atom in their structure, they are presented in two enantiomeric forms. It was reported by many studies that only the (S)-enantiomers of these drugs possess the desired therapeutic effect, whereas the administration of the racemate may cause dangerous side effects, such as bronchoconstriction or diabetes. Nevertheless, β- blockers are still commercially available drugs mainly used in medicine as racemates, whereas there are several methods that are widely used in order to obtain enantiomerically pure compounds.

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Samir, Liza, Rasha Hanafi, Sami El Deeb, and Hilde Spahn-Langguth. "UHPLC Enantiomer Resolution for the ɑ/β-Adrenoceptor Antagonist R/S-Carvedilol and Its Major Active Metabolites on Chiralpak IB N-5." Molecules 27, no. 15 (August 5, 2022): 4998. http://dx.doi.org/10.3390/molecules27154998.

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Carvedilol (CAR), a racemic lipophilic aryloxy propanolamine, acts as a selective α1-adrenoreceptor antagonist and a nonselective β-adrenoreceptor antagonist. CAR metabolism mainly produces three active metabolites: desmethyl carvedilol (DMC), 4′-hydroxy carvedilol (4′OHC) and 5′-hydroxy carvedilol (5′OHC). The oxidative S-(-)-metabolites contribute to the β-antagonistic effect, yet not to the α-antagonistic effect to be observed after drug dosage. Therefore, the three β-adrenoceptor blocking metabolites, which are structurally closely related to the parent CAR, are included into the development of a bioanalytical quantitative method for all major active species relevant with respect to adrenoceptor-blockade. Because of the given pharmacological profile, resolution of the enantiomers of carvedilol, of 4′- and 5′-hydroxy carvedilol as well as of DMC, is mandatory. The current study aims to determine the response surface for the enantiomer separation of the parent CAR as well as the major metabolites on a suitable chiral stationary phase. Design of experiment approach (DoE) was utilized in an initial screening phase followed by central-composite design for delimitation of the response surface for resolution of the four enantiomeric pairs in least run time. The impact of chromatographic variables (composition and percentage of organic modifier(s), buffer type, buffer pH, flow rate) on critical peaks resolution and adjusted retention time was evaluated, in order to select the most significant critical quality attributes. On this basis, a robust UHPLC-UV method was developed and optimized for the simultaneous, enantioselective determination of CAR along with its major active metabolites (4′OHC, 5′OHC, and DMC) on Chiralpak IBN-5. The optimized UHPLC-UV method (which includes metoprolol as the internal standard) was validated according to the ICH M10 guidelines for bioanalytical methods and proven to be linear, precise, accurate, and robust. The validated assay was applied to plasma samples from cardiovascular patients treated with rac-CAR (blood randomly drawn at different times after oral CAR intake). In order to provide more insight into the mechanism of the enantiomer separation of CAR and its metabolites on the CSP, docking experiments were performed. Molecular simulation studies suggest the chiral recognition to be mainly due to different binding poses of enantiomers of the same compound.

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Adrjanowicz, K., K. Kaminski, M. Tarnacka, K. Szutkowski, L. Popenda, G. Bartkowiak, and M. Paluch. "The effect of hydrogen bonding propensity and enantiomeric composition on the dynamics of supercooled ketoprofen – dielectric, rheological and NMR studies." Physical Chemistry Chemical Physics 18, no. 15 (2016): 10585–93. http://dx.doi.org/10.1039/c6cp00578k.

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Venkatakrishnarao, Dasari, Chakradhar Sahoo, Evgeniy A. Mamonov, Vladimir B. Novikov, Nikolai V. Mitetelo, Sri Ram G. Naraharisetty, Tatiana V. Murzina, and Rajadurai Chandrasekar. "Chiral organic photonics: self-assembled micro-resonators for an enhanced circular dichroism effect in the non-linear optical signal." Journal of Materials Chemistry C 5, no. 47 (2017): 12349–53. http://dx.doi.org/10.1039/c7tc04621a.

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Zhou, Liang-Mo, Meng-Yan Nie, Qing-Hai Wang, Dao-Qian Zhu, and He-Qing Shen. "Enthalpy-entropy compensation effect in gas chromatographic enantiomeric separation." Chinese Journal of Chemistry 17, no. 4 (August 27, 2010): 363–76. http://dx.doi.org/10.1002/cjoc.19990170409.

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Li, Zhi Wei, Xing Jia, Chun Mei Xu, Lei Liu, and De Cai Fu. "Chiral Separation of Amlodipine and its Enantiomer on a Molecularly Imprinted Polymer-Based Stationary Phase." Advanced Materials Research 706-708 (June 2013): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.36.

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A new chiral stationary phase for amlodipine (3-ethyl 5-methyl-2 -[(-2-(aminoethoxymethyl)-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridinedicarboxylate) based on a molecularly imprinted polymer has been prepared by radiation polymerization method and used for chromatographic separation of the chiral enantiomers. The effects on the separation of mobile phase and flow rate were investigated, and the optimum conditions for HPLC were shown to be: mobile phase, chloroform; flow rate, 0.3 ml min-1; at room temperature. The results has shown that the amlodipine-imprinted polymer was capable of recognizing the enantiomeric difference between the template and its R-enantiomer, whereas the non-imprinted and thermal polymerization polymer have no chiral recognition ability for the enantiomers.

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Ahmed, Hytham, Abdel-Aziz Wahbi, Hatem Elmongy, Ahmad Amini, Hirsh Koyi, Eva Branden, and Mohamed Abdel-Rehim. "Determination and Pharmacokinetics of Omeprazole Enantiomers in Human Plasma and Oral Fluid Utilizing Microextraction by Packed Sorbent and Liquid Chromatography-Tandem Mass Spectrometry." International Journal of Analytical Chemistry 2021 (January 19, 2021): 1–8. http://dx.doi.org/10.1155/2021/8845139.

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In the present work, the determination of omeprazole (OME) enantiomers in oral fluid and plasma samples was carried out utilizing microextraction by packed sorbent (MEPS) and liquid chromatography-tandem mass spectrometry. A chiral column with cellulose-SB phase was used for the first time for enantiomeric separation of OME with an isocratic elution system using 0.2% ammonium hydroxide in hexane-ethanol mixture (70 : 30, v/v) as the mobile phase. OME enantiomers were determined utilizing a triple quadrupole tandem mass spectrometer in positive ion mode (ESI+) monitoring mass transitions: m/z 346.3 ⟶ 198.0 for OME and m/z 369.98 ⟶ 252.0 for internal standard. The limits of detection and quantification of the present method for both enantiomers were 0.1 and 0.4 ng/mL, respectively. The method validation provided good accuracy and precision. The matrix effect factor was less than 5%, and no interfering peaks were observed. The interday precision values ranged from 2.2 to 7.5 (%RSD), and the accuracy of determinations varied from −9.9% to 8.3%. In addition, the pharmacokinetics (PK) of omeprazole enantiomers in healthy subjects after a single oral dose was investigated. (S)-Enantiomers showed higher levels than (R)-enantiomers throughout 24 h. It was found that the mean maximum concentrations of (R)- and (S)-omeprazole in plasma samples were about two times higher than in oral fluid.

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Toribio, Laura, Irene Magdaleno, Beatriz Martín-Gómez, María T. Martín, Silvia Valverde, and Ana M. Ares. "Study of Different Chiral Columns for the Enantiomeric Separation of Azoles Using Supercritical Fluid Chromatography." Separations 10, no. 1 (December 23, 2022): 9. http://dx.doi.org/10.3390/separations10010009.

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The enantiomeric separation of antifungal compounds is an arduous task in pharmaceutical and biomedical fields due to the different properties that each diastereoisomer presents. The enantioseparation of a group of fungicides (sulconazole, bifonazole, triadimefon and triadimenol) using supercritical fluid chromatography was achieved in this work. For this goal, four different chiral columns based on polysaccharide derivatives, as well as the effect of different chromatographic parameters such as temperature, type and percentage of organic modifier (methanol, ethanol and isopropanol), were thoroughly investigated. The inversion of the elution order of enantiomers as a result of a change in the stationary phase or organic modifier was also evaluated by employing a circular dichroism detector. The best separation conditions, in terms of the enantioresolution and analysis time, were obtained with the Lux® Cellulose-2 column using isopropanol as the organic modifier.

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Kordestani, Nazanin, Hadi Amiri Rudbari, Isabel Correia, Andreia Valente, Leonor Côrte-Real, Mohammad Khairul Islam, Nicola Micale, et al. "Heteroleptic enantiopure Pd(ii)-complexes derived from halogen-substituted Schiff bases and 2-picolylamine: synthesis, experimental and computational characterization and investigation of the influence of chirality and halogen atoms on the anticancer activity." New Journal of Chemistry 45, no. 20 (2021): 9163–80. http://dx.doi.org/10.1039/d1nj01491a.

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Chan, Ching W., Erik Laurini, Paola Posocco, Sabrina Pricl, and David K. Smith. "Chiral recognition at self-assembled multivalent (SAMul) nanoscale interfaces – enantioselectivity in polyanion binding." Chemical Communications 52, no. 69 (2016): 10540–43. http://dx.doi.org/10.1039/c6cc04470k.

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We investigate structure–activity effect relationships at the nanoscale chiral molecular recognition interface between enantiomeric self-assembled multivalent (SAMul) systems and biological polyanions, heparin and DNA.

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Tsarev, V. N., N. G. Bazarnova, and I. V. Mikushina. "Development of a Preparative Method for Obtaining an Enantiomerically Pure Substance of Salbutamol by Supercritical Fluid Chromatography." Drug development & registration 11, no. 4 (November 27, 2022): 160–69. http://dx.doi.org/10.33380/2305-2066-2022-11-4-160-169.

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Introduction. An increasing number of studies conducted in various countries in the field of biopharmacy convincingly show the differences in the physiological effects on the human body of stereoisomers of pharmaceutical substances. As a rule, one of the enantiomers has the necessary pharmacological effect, the other enantiomer is either inert or has a negative side effect. Currently, it is important to obtain enantiomerically pure pharmacological substances from their racemic mixtures.Aim. Obtaining the R-isomer of salbutamol from a racemic mixture of salbutamol and developing a preparative procedure for chiral separation by supercritical fluid chromatography (SFC) with a yield of the target product sufficient for the production process.Materials and Methods. Supercritical fluid chromatography (SFC) is widely used for analytical and preparative separations of enantiomers of pharmaceutical substances. The relevance of the use of supercritical fluid chromatography SFC is largely due to the fact that it uses sub- or supercritical carbon dioxide (SC-CO2) as the main component of the mobile phase (MP). Studies were carried out on semi-preparative Investigator SFC (Waters Corporation, USA) and preparative Prep 200 qSFC (Waters Corporation, USA) supercritical fluid chromatographs with PDA detectors. Samples were weighed to the nearest 0.0001 g on a XPE206DR balance (Mettler Toledo, USA).Results and discussion. The process of chiral separation of salbutamol sulfate by the SFC method on Prep 200 qSFC (Waters Corporation, USA) was studied. It was revealed that in the chromatographic system under supercritical conditions, the salt is separated into acidic and basic residues, which significantly reduces productivity and shortens the duration of continuous operation of the chromatograph. Conditions for the preparative chiral separation of the racemic mixture of salbutamol base into R- and S-isomers with high enantioselectivity and productivity have been developed. The resulting R-isomer of salbutamol base can be converted into the pharmaceutical substance in the form of sulfate or other salt without loss of enantiomeric purity, the S-isomer can be subjected to racemization and subsequent use.Conclusion. A preparative method has been developed for the chiral separation of a racemic mixture of salbutamol by supercritical fluid chromatography (SFC) with a yield of the target product (R-isomer) of 5.5 g per shift (8 hours).

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Journal articles on the topic 'Enantiomeric effect'

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