Direct Separation of Pregabalin Enantiomers Using a Zwitterionic Chiral Selector by High Performance Liquid Chromatography Coupled to Mass Spectrometry and Ultraviolet Detection.

Lakshmi Chennuru,Ramakrishna Nandula,Thirupathi Choppari,Pilar Franco,Tong Zhang

doi:10.3390/molecules21111578

Abstract

The chromatographic resolution of pregabalin enantiomers has been often achieved by derivatization of the molecule, in order to reach enough sensitivity at low concentrations of the minor enantiomer present in the active principle. In the present article, the development and optimization of two liquid chromatographic methods are presented for the direct resolution of pregabalin enantiomers on a chiral stationary phase (CSP) containing a zwitterionic selector derived from cinchona alkaloid and sulfonic acid (CHIRALPAK ZWIX). The key parameters for the separation as well as the compatibility of chromatographic conditions with different detection modes (ultraviolet and mass spectrometry) were investigated. The resulting methods were found to be selective, of high performance and low limits of detection (2 µg/mL by UV and 1 ng/mL by MS, respectively) and quantification (6 µg/mL by UV and 5 ng/mL by MS, respectively) for the minor enantiomer which is considered as a chiral impurity.

Highlights

Pregabalin (PRG), (S)-3-(aminomethyl)-5-methylhexanoic acid), is an antiepileptic and analgesic drug
A recent screening study on the immobilized amylose- and cellulose-derived chiral stationary phase (CSP) was leading to a successful separation of PRG from its (R)-enantiomer on a CHIRALPAK IE column (amylose tris(3,5-dichlorophenylcarbamate) immobilized on spherical silica, using a n-hexane/EtOH/trifluoro acetic acid (TFA)/NH3 (80/20/0.3/0.3, v/v/v/v) mobile phase
The chiral impurity was eluted after the main PRG peak

Summary

Introduction

Pregabalin (PRG), (S)-3-(aminomethyl)-5-methylhexanoic acid), is an antiepileptic and analgesic drug. It is a structural analogue of the endogenous inhibitory neurotransmitter γ-aminobutyric acid (GABA), which is involved in the regulation of brain neuronal activity [1]. Enantiomers of a drug are often known to have differences in pharmacological actions, in pharmacokinetics, in toxicities and in metabolism. The use of a single isomer of a given drug is usually recommended for clinical use [5]. PRG is the (S)-enantiomer of a γ-amino acid containing one stereogenic carbon (Figure 1a). While PRG is proved to have significant clinical relevance, its (R)-enantiomer (Figure 1b) has been reported to be 10 times less active in biological

Objectives

Methods

Results

Conclusion