Enantiomeric separation of azelnidipine by high performance liquid chromatography with chiral stationary phase

Stability-indicating LC Method for Quantification of Azelnidipine: Synthesis and Characterization of Oxidative Degradation Product

Objectives

In the work presented here, the degradation behavior of azelnidipine under diverse forced degradation conditions was studied. A stability-indicating liquid chromatographic method was established which could separate and resolve azelnidipine from its degradation products. Further, chemical kinetics under acidic and alkaline conditions were studied, and validation studies were performed.

Materials and Methods

Using reversed-phase chromatography, azelnidipine and its formed degradants were resolved using phosphate buffer (pH 3.0) and methanol in a mixture of 10:90% v/v as a mobile phase at a flow rate of 1.0 mL/min. All eluents were detected at a wavelength of 256 nm.

Results

Azelnidipine was degraded under acid, alkali, wet heat, and oxidized environment. The pH-dependent rate of hydrolysis of azelnidipine was studied under acidic and alkaline conditions and chemical kinetics were determined. Further, the oxidative degradation product of azelnidipine was synthesized and characterized as 3-(1-benzhydrylazetidin-3-yl) 5-isopropyl 2-amino-6-methyl-4-(3-nitrophenyl) pyridine-3,5-dicarboxylate (dehydro-AZD).

Conclusion

The susceptibility of azelnidipine to hydrolysis was attributed to the presence of ester at 3 and 5 positions of 1,4 dihydropyridine. Further, under oxidative conditions, the aromatization of 1,4 dihydropyrinine resulted in dehydro-AZD. Azelnidipine followed the first-order reaction under acid and alkali hydrolysis, and was more susceptible to degradation under acidic conditions. The synthesized and confirmed dehydro-AZD was found as one of the metabolites and impurities of azelnidipine. The evaluated validation parameters ascertained the practicality of the method for the quantification of azelnidipine tablets.

Liquid Chromatographic Enantioseparation of Some Fluoroquinoline Drugs Using Several Polysaccharide-Based Chiral Stationary Phases

The enantioseparation of three fluoroquinoline antibacterial drugs, namely, flumequine, ofloxacin and lomefloxacin using high-performance liquid chromatography was optimized on seven polysaccharide-derived chiral stationary phases, namely, Chiralpak® IB, chiralpak® IA, Chiralpak® AD, Chiralcel® OJ, Chiralcel® OD, Chiralcel® OD-H and Chiralcel® OZ-3 and applying different mobile phases in isocratic mode is described. The role of addition of organic additives was also investigated. A baseline separation of flumequine, ofloxacin and lomefloxacin enantiomers was achieved. Parameters influencing enantioseparation including mobile phase, organic additive and chemical nature of the chiral selector found to be highly influencing on the enantiomeric separation were investigated. Chiral recognition mechanism(s) are also presented.