CHIRAL RP-HPLC ASSAY FOR PROPAFENONE ENANTIOMERS IN RAT LIVER MICROSOMAL INCUBATES AND ITS APPLICATION IN VITRO METABOLISM

AIM　To separate propafenone enantiomers in rat liver microsomal incubates and investigate probable stereoselectivity in their N-dealkylation. METHODS　The concentration of each enantiomer in rat liver microsomal incubates was determined through precolumn derivatization with 2,3,4,6-tetra-O-acetyl-β-glucopyranosyl isothiocyanate (GITC), followed by RP-HPLC assay. RESULTS　A baseline separation of propafenone enantiomers was achieved on C₁₈-ODS column, with methanol — water — glacial acetic acid (67∶33∶0.05) as mobile phase. The assay was linear from 0.5 to 320 μg*mL^-1 for each enantiomer, and the limit of detection was 100 ng*mL^-1. The method affords the average recoveries of 77.1% for R-propafenone and 76.0% for S-propafenone. Stereoselectivity was observed for the phase I metabolism of racemic propafenone in dexamethasone, β-naphthoflavone induced rat liver microsomal incubates,but not in controls. CONCLUSION　The method is simple, cheap and can be applied to study the metabolism of R- and S-propafenone in vitro. Stereoselectivity exists in their N-dealkylation.