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Article

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

1
Centre for the Control and Evaluation of Medicines, Chemical Medicines Unit, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
2
Department of Chemistry and Technology of Drugs, Sapienza University of Rome, 00185 Rome, Italy
*
Author to whom correspondence should be addressed.
Academic Editors: Paola Peluso and Victor Mamane
Molecules 2021, 26(6), 1747; https://doi.org/10.3390/molecules26061747
Received: 12 February 2021 / Revised: 4 March 2021 / Accepted: 17 March 2021 / Published: 20 March 2021
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. View Full-Text
Keywords: amylose-based CSPs; chiralpal AS-H; chiralpak IH-3; enantioselective HPLC; α-lipoic acid; α-dihydrolipoic acid; absolute configuration amylose-based CSPs; chiralpal AS-H; chiralpak IH-3; enantioselective HPLC; α-lipoic acid; α-dihydrolipoic acid; absolute configuration
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MDPI and ACS Style

Rosetti, A.; Villani, C.; Pierini, M.; Cirilli, R. 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 2021, 26, 1747. https://doi.org/10.3390/molecules26061747

AMA Style

Rosetti A, Villani C, Pierini M, Cirilli R. 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. 2021; 26(6):1747. https://doi.org/10.3390/molecules26061747

Chicago/Turabian Style

Rosetti, Alessia, Claudio Villani, Marco Pierini, and Roberto Cirilli. 2021. "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: 1747. https://doi.org/10.3390/molecules26061747

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