Chiral molecules in relation to particular biological roles are stereoselective. Enantiomers differ significantly in their biochemical responses in biological environment. Despite the current advancement in drug discovery and pharmaceutical biotechnology, the chiral separation of some racemic mixtures continues to be one of the greatest challenges, because the available techniques are too costly and time consuming for the assessment of therapeutic drugs in the early stages of development worldwide. Various nanoparticles became one of the most investigated and explored nanotechnology‐derived nanostructures especially in chirality where several studies are reported to improve enantiomeric separation of different racemic mixtures. The production of surface‐modified nanoparticles has contributed to these limitations in terms of sensitivity, accuracy, and enantioselectivity that can be optimized and therefore makes these surface‐modified nanoparticles convenient for enantiomeric identification and separation.

BACKGROUND The determination of enantio‐separation, absolute configuration and chiral recognition mechanism of ofloxacin and flumequine was carried out by high‐performance liquid chromatography (HPLC) and modeling studies. The column used was a Chiralcel OD‐H with normal and polar organic mobile phase modes. The exhaustive chiral separation was optimized through various HPLC parameters. RESULTS The selectivity, separation factors and resolution factors for ofloxacin were 8.2 and 9.4, 1.15 and 2.43 in the normal mobile phase, while these values were 10.5 and 12.0, 1.14 and 2.40 for flumequine in polar organic mobile phase mode, respectively. The thermodynamic parameters were ΔH (−0.137 J mol−1), ΔS (7.35 × 10−4 J mol−1) and ΔG (−0.360 J mol−1 K−1) for ofloxacin, and ΔH (−0.035 J.mol−1), ΔS (21.3 × 10−4 J mol−1) and ΔG (−0.105 J mol−1 K−1) for flumequine, confirming spontaneous chiral separation at all temperatures. The chiral recognition mechanism was established by HPLC and modeling results. The modeling binding affinity were −2.5 kcal mol–1 (R‐enantiomer) and −2.6 kcal mol–1 (S‐enantiomer) for ofloxacin, and −2.30 kcal mol–1 (R‐enantiomer) and −2.40 kcal mol–1 (S‐enantiomer) for flumequine enantiomers. The chiral resolution is controlled by hydrogen bonding, π–π interactions and other forces. CONCLUSION These methods were applied to monitor ofloxacin and flumequine quinolones in urine samples. Briefly, the developed chiral HPLC methods are effective and may be used to analyze the reported enantiomers in any biological sample. © 2021 Society of Chemical Industry (SCI).

Four racemic iminoflavan derivatives were synthesized by simple condensation at C-4 position of flavanone. All new compounds were characterized by using ultraviolet-visible, infrared, and nuclear magnetic resonance spectroscopic techniques. A chiral chromatographic analysis of racemic mixtures was performed by direct chiral high-performance liquid chromatography using Chiralcel R OD-H as chiral stationary phase, and online-coupled with electronic circular dichroism detector. The correlation of experimental electronic circular dichroism traces with quantum chemical electronic circular dichroism calculations run with time-dependent density functional theory made it possible to elucidate the absolute configuration for each enantiomer, and to establish the elution order.

The enantioseparation of three fluoroquinoline antibacterial drugs, namely, flumequine, ofloxacin and lomefloxacin using high-performance liquid chromatography was optimized on seven polysaccharide-derived chiral stationary phases, namely, Chiralpak® IB, chiralpak® IA, Chiralpak® AD, Chiralcel® OJ, Chiralcel® OD, Chiralcel® OD-H and Chiralcel® OZ-3 and applying different mobile phases in isocratic mode is described. The role of addition of organic additives was also investigated. A baseline separation of flumequine, ofloxacin and lomefloxacin enantiomers was achieved. Parameters influencing enantioseparation including mobile phase, organic additive and chemical nature of the chiral selector found to be highly influencing on the enantiomeric separation were investigated. Chiral recognition mechanism(s) are also presented.