Enantioseparation of chiral ofloxacin using biomacromolecules

摘要

Natural biomacromolecules including bovine serum albumin (BSA), calf thymus DNA (ct-DNA) and fish sperm DNA (fs-DNA) were studied as the free chiral selectors to separate R- and S-ofloxacin enantiomers from racemic ofloxacin, combined with ultrafiltration and subsequent crystallization. First, the interactions between chiral ofloxacin and biomacromolecules including BSA, ct-DNA, and fs-DNA were investigated using circular dichroism and fluorescence spectroscopy. BSA exhibited stereoselective adsorption towards R-ofloxacin at pH 9.0 with an enantioselectivity of 1.23, while ct-DNA showed enantiospecific interaction with S-enantiomer with the selectivity of 1.70 at pH 5.0. One single-stage adsorption by BSA provides an enantiomeric excess in the permeate (e.e._p) of 14% in S-enantiomer, and five-stage operations enhance the chiral resolution to reach the e.e.,, value of 44%. R-enantiomer with an e.e._p, of -26% can be obtained through one single-stage adsorption by using ct-DNA, and -85% can be reached by five-stage operations. Enantiomeric mixtures with the intial e.e. of 44% (S-) can be upgraded to 95%) (S-) through subsequent crystallization. This programmable process of adsorption and desorption using BSA or ct-DNA as chiral selectors can be successfully applied to produce the enantiomers with highly optical purity.