Investigation on the chiral recognition site of enantioselective separation of ofloxacin by capillary zone electrophoresis using vancomycin as a chiral selector / 药学学报

The chiral recognition site of the macrocyclic antibiotic vancomycin, used as a chiral selector in capillary electrophoresis (CE), was studied with ofloxacin, antofloxacin (a new fluoroquinolone antibiotic under development) and R-antofloxacin, as well as with norvancomycin. Enantioselectivity of vancomycin and norvancomycin was compared. The influence of vancomycin concentration, pH of buffer, and separation voltage in CE were examined in order to investigate interactions between enantiomers and vancomycin. Furthermore, interactions of chiral selectors and enantiomers were calculated by molecular mechanics method with Chem 3D software. The result indicates that both vancomycin and norvancomycin have two domains in 3D structure, and the domain I of vancomycin was considered to be the chiral recognition site of ofloxacin. The degree of interaction between vancomycin and ofloxacin is determined as follows: hydrogen bond occurring with carboxylic group at C-6 of ofloxacin and hydroxyl group of sugar part of vancomycin, the matching degree of molecular sizes of ofloxacin with the pocket in domain I of vancomycin and the hydrophobic interaction between methyl group at C-10 of piperidine group of ofloxacin and N-methyl leucine of vancomycin.

Analysis of the response factors of different quinolones detected by evaporative light-scattering detector / 药学学报

<p><b>AIM</b>To analyze the response factors of different quinolone antibiotics detected by evaporative light-scattering detector (ELSD).</p><p><b>METHODS</b>The response factors of five different quinolones (enoxacin, levofloxacin, ciprofloxacin, lomefloxacin and gatifloxacin) detected by ELSD were determined by using a YMC-Pack ODS-AM cloumn (150 mm x 4.6 mm ID, 5 microns) as analytical column and 0.5% triethylamine (adjusting pH 2.5 with trifluoroacetic acid)-acetonitrile (48:12) as mobile phase at a flow rate of 0.6 mL.min-1, the temperature of the drift tube was set at 117 degrees C, and the flow of carrier gas at 3.0 L.min-1. Detector responses (A) and the amount of injection of each substance (m) were fitted to the logarithmic regression: log A = b log m + log a.</p><p><b>RESULTS</b>The linear regression equation obtained were: enoxacin: Y = 1.0799X + 2.7611, r2 = 0.9996; levofloxacin: Y = 1.0913X + 2.7235, r2 = 0.9997; ciprofloxacin: Y = 1.0828X + 2.7523, r2 = 0.9994; lomefloxacin: Y = 1.0891X + 2.7391, r2 = 0.9993; gatifloxacin: Y = 1.0878X + 2.7392, r2 = 0.9995. The differences between them were negligible.</p><p><b>CONCLUSION</b>Different quinolones can give the same responses with ELSD detection. So, the HPLC-ELSD methods can be applied to the determination of new substances by using another substance as reference.</p>