Affinity Adsorbents With D-Alanine And D,L-Alanine As Ligands For Vancomycin Group Antibiotics

Two affinity adsorbents for the vancomycin group antibiotics were prepared by immobilizing D-alanine and DL-alanine, respectively, onto crosslinked polyacrylamide resin through the Mannich reaction. The adsorption of N-demethylvancomycin on the adsorbents was studied. The results showed that the adsorption capacity of the D-alanine-immobilized adsorbent was higher than that of the D,L-alanine-immobilized one when the immobilization capacities were the same, indicating the affinity of the immobilized D-alanine for N-demethylvancomycin was greater than that of the immobilized L-alanine.Chromatographic adsorption and desorption of N-demethylvancomycin on a column packed with DL-alanine-immobilized adsorbent were carried out. The saturation adsorption capacity was similar to0.45 mmol/g (dry resin) or similar to0.064 mmol/mL (swollen resin) when the initial concentration of N-demethylvancomycin was 6.62 mM. The adsorbed N-demethylvancomycin on the column was eluted using 0.1 M HCl in water/ethanol (7/3, v/v) as eluant.There were two peaks in the elution curve. The first peak (with lower elution volume) may have resulted from the N-demethylvancomycin being adsorbed by the immobilized L-alanine, while the second peak may correspond to the N-demethylvancomycin adsorbed by the immobilized D-alanine. The area ratio of the first peak to that of the second one was similar to1/4, indicating that the immobilized D-alanine adsorbed more N-demethylvancomycin than the immobilized L-alanine.