Cellulose tris-(3,5-dimethyl phenyl carbamate) as a chiral stationary phase for enantiomeric determination of ofloxacin enantiomers and molecular docking study on the chiral separation mechanism

In the present work, direct chiral separation of ofloxacin enantiomers was conducted using a Chiral MD (2) column as a chiral stationary phase (CSP) by a normal phase HPLC method, and then applied to enantiomeric quality control of two commercial pharmaceuticals containing the ofloxacin racemate and S-enantiomer, respectively. Experimental results indicated that the simultaneous addition of acid and alkaline additives to the mobile phase was important for improving the enantiomeric resolution. Combined with the molecular docking research, we found that the difference in the binding energy of each enantiomer interacting with CSP reached the maximum when the ofloxacin molecule was non-ionized. That is why both the acid and alkaline additives are necessary in the enantioseparation. Computer simulation results further revealed that hydrogen bonding, hydrophobic effects and pi-pi stacking were all involved in the stereoselective interaction, causing the difference in the binding strength with CSP, which eventually resulted in the chiral separation of the ofloxacin enantiomers.

Automated summary

In this study, direct chiral separation of ofloxacin enantiomers using a Chiral MD (2) column as a chiral stationary phase (CSP) by normal phase HPLC method was achieved, and the method was applied to the quality control of two commercial pharmaceuticals containing ofloxacin racemate and S-enantiomer, respectively. The results showed that the addition of acid and alkaline additives to the mobile phase simultaneously was crucial for improving the enantiomeric resolution. Molecular docking research revealed that the binding energy difference between each enantiomer and CSP was maximized when the ofloxacin molecule was non-ionized, explaining the necessity of both acid and alkaline additives in the enantioseparation. Computer simulation results further demonstrated the involvement of hydrogen bonding, hydrophobic effects, and pi-pi stacking in the stereoselective interaction, leading to the chiral separation of ofloxacin enantiomers.