Rapid and economic chiral-HPLC method of nebivolol enantiomers resolution in dosage formulation Zeid A. Al-Othman a and Imran Ali b * ABSTRACT: A fast, economic, reproducible, accurate, effective, rugged and selective chiral-HPLC method was developed and validated for the enantiomeric resolution of nebivolol enantiomers [(+)-RRRS and ()-SSSR)] in dosage formulation. The method was rapid as chiral separation occurred within only 12 min. The mobile phase used was n-heptane–ethanol–DEA (85:15:0.1, v/v) at 3.0 mL/min flow-rate with 225 nm detection. The column used was an amylase-based 3-AmyCoat (150  46 mm) [tris-(3,5-dimethylphenyl carbamate)]. The capacity factors of (+)-RRRS and ()-SSSR enantiomers were 7.85 and 10.90 while the separation and resolution factors were 1.39 and 1.83, respectively. The limits of detection and quantita- tion for (+)-RRRS enantiomer were 4.5 and 10.00 mg/mL, while these values for ()-SSSR enantiomer were 4.1 and 8.2 mg/mL, respectively. The linearity was observed in the concentrations range of 0.10–1.0 mg/mL for both enantiomers. The p–p interactions, hydrogen bonds, dipole–dipole interactions and steric effects control the chiral resolution of nebivolol enantio- mers on the reported chiral column. The reported method can be used for the quality control of nebivolol in pharmaceutical preparations with good economy. In addition, this method can also be used for the analysis of (+)-RRRS and ()-SSSR) enantiomers in biological and environmental samples. Copyright © 2011 John Wiley & Sons, Ltd. Keywords: nebivolol enantiomers; 3-AmyCoat column; extraction; chiral-HPLC; validation; pharmaceutical analyses Introduction b-Blockers are used worldwide for various cardiovascular diseases such as hypertension, angina pectoris and cardiac arrhythmias (Ali et al., 2009a). All b-blockers are found in racemic forms (Meyers et al., 1980) with S-()-enantiomers about 50–500 times more pharmaceutically active than their corresponding R-(+)-antipodes. It is well known that the inactive enantiomers may be, toxic, inactive or ballast, leading to various side effects and toxicities (Barrett and Cullum, 1968; Nelson and Burke, 1978; Walle et al., 1984; Lee and William, 1990; Schmid et al., 2001). Moreover, long-term use of these racemic drugs may cause diabetes in hypertensive patients (Balmer et al., 1992; Cherezov et al., 2007; Belknap, 2008; Ram, 2008). The US FDA (FDA, 1992), the European Committee for Proprietary Medicinal Products (Aboul-Enein and Ali, 2003), Health Canada (Health Canada, 2000) and Pharmaceutical and Medical Devices Agencies of Japan (Shimazawa et al., 2008) have banned the marketing of all racemic b-blockers. In view of these facts, scientists have been compelled to develop optically active pure drugs. In addition, chiral analysis of b-adrenergic blockers is also important for enantiomeric pharmacokinetic and pharmacody- namic studies. Among the various b-adrenergic blockers, nebivolol (Fig. 1) has superior vasodilating properties (Janssen et al., 1989; Gao et al., 1991; Himmlmann et al., 1996; Cheymol et al., 1997). Nebivolol is a very promising b-blocker with selective b-andrenergic receptor antagonizing properties and lacking intrinsic sympathomimetic activities (Janssen et al., 1989). Besides, nebivolol relaxes coronary arteries (Gao et al., 1991) resulting into immediate decrease of blood pressure, hence, it is supposed as the best antagonist with vasodilating properties (Van de Water et al. 1988; Himmlmann et al., 1996; Van Bortel et al. 1997). Nebivolol contains four chiral centers and occurs in 10 enantiomers owing to meso forms in six enantiomers because of the presence of a center of symmetry in them. On the other hand, out of 10 enantiomers only (+)-RRRS and ()-SSSR are biologically active with the former 100 times more active than the later antipode (Cheymol et al., 1997). Moreover, it is interesting to observe that ()-SSSR enantiomer potentiates the hypotensive effect of (+)-RRRS nebivolol enantiomer (Janssen et al., 1991). Among the various techniques available, chiral HPLC is the best method for monitoring enantiomers of b-blockers in dosage formulations (Ali et al., 2009b). Different chiral stationary phases (CSPs) have been used for enantiomeric resolution. However, the polysaccharide CSPs are the best as about 95% of racemates can be resolved on them successfully (Zhang et al., 2005). A literature survey shows few papers on chiral separation of nebivolol (Aboul-Enein and Ali, 2001a, b; Ghanem et al., 2006) with high retention times, involving costly solvents. Moreover, there is no paper on the chiral separation of nebivolol in dosage formulation. Nowadays, speed and economy are the most important aspects of chiral-HPLC analyses, including * Correspondence to: Imran Ali, Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India. E-mail: drimran_ali@yahoo.com a Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia b Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110025, India Abbreviations used: CSP, chiral stationary phase; DEA, diethylamine. Biomed. Chromatogr. 2012; 26: 775–780 Copyright © 2011 John Wiley & Sons, Ltd. Research article Received: 3 August 2011, Accepted: 10 September 2011 Published online in Wiley Online Library: 27 October 2011 (wileyonlinelibrary.com) DOI 10.1002/bmc.1728 775