Enantioselective analysis of ranolazine and desmethyl ranolazine in microsomal medium using dispersive liquid-liquid microextraction and LC-MS/MS.

Background: An enantioselective bioanalytical method using dispersive liquid–liquid microextraction (DLLME) and LC–MS/MS was developed for the chiral analysis of ranolazine (RNZ) and one of its metabolites (desmethyl ranolazine [DRNZ]). Results: The analytes were extracted from microsomal medium by DLLME, using chloroform as extractor solvent and acetone as dispersive solvent. The enantiomers of RNZ and DRNZ were analyzed simultaneously for the first time using a Chiralcel OD-H®. Method validation showed recoveries in the order of 55 and 45%, and LLOQ of 25 and 10 ng ml-1 for the enantiomers of RNZ and DRNZ, respectively. Linearity was established in the concentration range of 10 to 1000 and 25 to 2500 ng ml-1 for each DRNZ and RNZ enantiomer, respectively. Conclusion: The unprecedented use of DLLME was demonstrated to be very useful for sample preparation of microsomal matrix. Furthermore, the in vitro metabolism of RNZ was enantioselective.