Enantioseparation Of Ofloxacin Through Biomacromolecules

Chirality, the most intriguing phenomenon in living organisms, has attracted increasing attentions in the pharmaceutical industry, owing to great differences in pharmacological, toxicological and/or metabolic activities of enantiomeric drugs in living systems. In2010, seven of the top ten biggest-selling prescription drugs are chiral drugs. Biomacromolecules of proteins and nucleic acids, with the advantage of inherent chiral properties and no cellular toxicity, have been considered as promising alternatives to separate racemic mixtures. In this research, we develop an effective approach of enantiomeric enrichment of ofloxacin enantiomers using BSA and ct-DNA as the enantioselective ligands respectively, combining with ultrafiltration and subsequent crystallization.Firstly, the interactions between chiral ofloxacin and biomacromolecules including BSA, ct-DNA, and fs-DNA are investigated using circular dichroism and fluorescence spectroscopy, and found that R-enantiomer preferential bind to BSA, S-enantiomer preferential bind to ct-DNA, but there was no chiral separation performance of fs-DNA. Secondly, the influence of pH and the concentration of chiral selector on the chiral separation performance were studied, for BSA, the enantiomeric excess in the permeate (e.e.p) value reaches the highest of10%in S-ofloxacin at pH9.0. While using ct-DNA selector, the highest e.e.p value is-14%in R-ofloxacin at pH5.0. The optimum separation conditions were achieved through BSA with the concentration of0.3mM, or with3mM ct-DNA base. Thirdly, multistage ultrafiltration was used to upgrade S-and R-ofloxacin. Five-stage adsorption by BSA gives an e.e.p of44%(S) in S-enantiomer. R-enantiomer with an e.e.p of-85%(R) can be obtained through five-stage adsorption by ct-DNA. Finally, the enantiomeric mixtures at the starting e.e. of44%(S) can be upgraded to95(S) through subsequent crystallization. This article attempts to immobilize BSA onto the surface of polysulfone ultrafiltration membrane, ATR-FTIR analysis implied that BSA can graft onto the surface polysulfone membrane.