Chiral separation of aromatic amino acids by capillary electrophoresis using sulphated β-cyclodextrin as a single chiral selector: an experimental and computational study

Abstract

Chiral discrimination of aromatic amino acids is crucial in biochemical, pharmaceutical and analytical sciences, yet a clear and mechanistic understanding of cyclodextrin-mediated enantioseparation in capillary electrophoresis (CE) remains incomplete. In this work, the enantioseparation of tryptophan (TRP), tyrosine (TYR), and phenylalanine (PHE) was studied by capillary electrophoresis (CE) using sulphated β-cyclodextrin (S-β-CD) as a single chiral selector under acidic buffer conditions. Separation parameters, including S-β-CD concentration and background electrolyte (BGE) pH, were systematically investigated. Base line separation of the three analytes was achieved using 1.5 mM S-β-CD in 25 mM phosphate buffer at pH 2.5. In addition to analytical performance, the contribution of this study lies in correlating experimental enantiomer migration behavior with qualitative molecular docking analysis to rationalize chiral recognition trends. Docking simulations were performed using sulphated β-cyclodextrin models with substitution degrees representative of the experimental material, allowing comparison of predicted host–guest inclusion tendencies for the individual enantiomers. Molecular docking studies, together with experimental results, indicate that the R-enantiomers tend to form more stable inclusion complexes with S-β-CD, which is consistent with their later elution under the applied CE conditions.