HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ISOLATION AND SPECTROSCOPIC CHARACTERIZATION OF 3 MAJOR METABOLITES FROM THE PLASMA OF RATS RECEIVING RAPAMYCIN (SIROLIMUS) ORALLY

Three major metabolites of rapamycin (M2, M3, and M5) were isolated fr om pooled plasma of orally dosed rats. Metabolites were extracted from the plasma with ethyl acetate/methanol prior to isolation by HPLC usi ng a Supelcosil SPLC-18, 5 mu m, IO x 250 mm column. The mobile phase was a methanol/ammonium acetate linear gradient system. The isolated m etabolites were characterized by negative ion FAB MS, ion-spray MS and ion-spray MS/MS. Metabolite M2 is oxygenated in the southern portion of rapamycin and the macrolide ring is opened. M3 is a structural isom er of rapamycin where the lactone ring is opened. M5 is O-demethylated on the C41 methoxy moiety and the macrolide ring is intact.