Determination of the in vitro metabolism of (+)- and (-)-epibatidine

The oxidative in vitro metabolism of epibatidine was investigated using liv er microsomes from rat, dog, rhesus monkey and human. Analysis was performe d using liquid chromatography-mass spectrometry (LC-MS) using both achiral and chiral stationary phases. Comparison of the metabolism of the (+)- and (-)-enantiomers revealed species differences in the extent of metabolism, w ith rhesus monkey>dog>rat=human. Furthermore, differences in the routes of metabolism for epibatidine enantiomers were also observed, with mass spectr a consistent with hydroxylation of the azabicycle for (-)-epibatidine and w ith the formation of diastereomeric N-oxides for (+)-epibatidine being obta ined. For chiral LC-MS, a volatile ion-pair reagent of heptafluorobutyric a cid was used in place of pentanesulphonic acid with no deterioration in chi ral selectivity. Analysis of the same samples by chiral LC-MS revealed no e vidence for metabolic chiral interconversion and chiral analysis from a met abolic time course of racemic material revealed enantiomers to be metabolis ed to approximately the same extent. Such findings may be important particu larly should epibatidine be investigated in non-rodent species. (C) 2000 El sevier Science B.V. All rights reserved.