Structure‐retention relationship for enantioseparation of selected fluoroquinolones

Abstract

Fluoroquinolones are popular class of antibiotics with distinct chemical functionality. Most of them are ampholytes with one chiral center. Stereogeneic center is located either in the side ring of Gatifloxacin (GFLX) or in the quinolone core of Ofloxacin (OFLX). These two amphoteric fluoroquinolones have terminal amino groups in common. The unusual Nadifloxacin (NFLX) is an acidic fluoroquinolone with a core chiral center. Owing to chirality and functionality differences among GFLX, OFLX, and NFLX, we mapped these enantiomers onto structure-retention relationship. Amount of acetic acid modifier was studied in screened mobile phase and cellulose tris(3-chloro-4-methyl phenyl carbamate) (Lux cellulose-2) stationary phase. Experimental design of acetic acid% along with column temperature have been applied. Resolution and enantioselectivity have been related to structural features of the studied enantiomers. High amount of acid (0.4%) was optimum for the separation of either side chirality with a proximate amino group (GFLX) or core chirality without basic functionality (NFLX), while low amount (0.2%) is optimum for core chiral center with distal amino group (OFLX). Temperature has no significant effect on resolution and retention of enantiomers except for OFLX. Enantio-retention explains possible chiral selective and nonselective interactions. The proposed methods have been validated for pharmaceutical analyses.

The impacts of Cu(II) complexation on gatifloxacin adsorption onto goethite and hematite

“…The acidic constants of GAT measured in this study using potentiometric titration were 6.25 and 9.45, respectively, which were close to the values of Hassan et al. () (i.e., 5.9 and 9.8) and other FQs with similar structures reported previously (Table ). The speciation of Cu(II)–GAT complexes greatly depended on the Cu(II) concentration and pH (Figure 1b–d).…”

Green method by National Environmental Methods Index and Eco‐Scale Assessment for evaluation of gatifloxacin‐based product by HPLC

“…In addition, over 77% of these methods use a 250‐mm column instead of smaller columns, such as 150 or 100 mm, which generates more waste. Furthermore, over 77% of these methods use a flow rate of 1.0 mL min −1 , which contributes to more waste generation compared with smaller flow rates (Aljuffali et al, 2015; El‐Gammal et al, 2018; Gandhi et al, 2016; Grace et al, 2019; Hassan et al, 2018; Razzaq et al, 2012; Razzaq et al, 2017; Saad et al, 2020; Venugopal et al, 2007). All these choices combined impact the sustainability, cost, and environmental friendliness/greenness of the method.…”

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

“…For example, S-ofloxacin has 8-128 times higher in vivo activity than the R-enantiomer. 3,4 Thus, to improve the efficacy and safety of ofloxacin, the S-enantiomer was specially manufactured for clinical application, which was also named levofloxacin.…”