Isolation from pig liver microsomes, identification by electrospray tandem mass spectrometry and in vitro immunosuppressive activity of a rapamycin tris‐epoxide metabolite

Abstract

It was demonstrated that rapamycin is metabolized in vitro by pig liver microsomes under the influence of the cytochrome P450‐dependent mixed function oxygenase system to a rapamycin tris‐epoxide metabolite, as demonstrated by electrospray tandem mass spectrometry . The in vitro immunosuppressive activity of this metabolite was found to be lower than that of rapamycin, probably because the rapamycin effector sector was structurally modified. The effector region of rapamycin was recognized to include the conjugated double bonds of this compound and metabolic reactions affecting this region may change the binding affinity of the rapamycin–FKBP binary complex towards another pharmacological receptor bound to the binary complex. Moreover, metabolic modifications in the effector region are probably able to induce a change in the binding affinities of the rapamycin–FKBP binary complex, including the pipecolic acid moiety and the lactone function of the parent drug. Copyright © 1999 John Wiley & Sons, Ltd.

In vitro immunosuppressive activity of tacrolimus dihydrodiol precursors obtained by chemical oxidation and identification of a new metabolite of SDZ‐RAD by electrospray and electrospray‐linked scan mass spectrometry

“…1), with a molecular mass of 957.57 Da [C 53 H 83 NO 14 ], like CsA, FK506 and RAPA, is primarily metabolized in the liver by the cytochrome P-450 3A enzymes 17 the metabolites produced result in either a mass increase of 16 units, corresponding to single hydroxylation, or in a mass decrease of 14 units, resulting from single Odemethylation of SDZ-RAD. 18 Epoxides and dihydrodiols were recently isolated from pig and rat liver microsomes 19,20 and identified by electrospray mass spectrometry (MS).…”

“…22 In addition, we describe in this report the identification of an SDZ-RAD C 16 , C 27 O-demethyl 17, 18-19, 20-21, 22 trisepoxide new metabolite isolated from pig liver microsomes. The SDZ- RAD 17,[18][19][20][21]22 tris-epoxide has already been isolated from pig liver microsomes and was identified by electrospray tandem MS (MS/MS). 21 The new metabolite was identified by electrospray and by electrospray-linked scan mass spectrometry.…”

Isolation from pig liver microsomes, identification by tandem mass spectrometry and in vitro immunosuppressive activity of an SDZ-RAD 17,18,19,20,21,22-tris-epoxide

“…8 We have recently identified, from pig liver microsomes, metabolites of rapamycin corresponding to epoxides and dihydrodiols resulting from the epoxide hydrase enzyme activity. 9,10 We describe here the isolation, identification by electrospray tandem mass spectrometry (ESIMS/MS) and the in vitro immunosuppressive activity using mixed lymphocyte reactions (MLR) of an SDZ-RAD 17,18,19, 20,21,22-tris-epoxide.…”

Analysis of Fatty Acyl Groups of Diacyl Galactolipid Molecular Species by HPLC/ESI-MS with In-source Fragmentation

“…primarily to analyze proteins, which are not only difficult to ionize under any circumstances, but also have molecules too large to be analyzed with a conventional mass spectrometer. Recently, ESI-MS has been widely applied to the analysis of glycoproteins, 9 oligonucleotides, 10,11 oligosaccharides, 12,13 drugs and drug metabolites, 14 environmental contaminants, 15,16 and numerous other types of compounds. 17 The combination of the fast atom bombardment (FAB) ionization method and tandem mass spectrometry (MS/MS) for the analysis of mixtures has largely improved the structural characterization of several high-mass lipids at the molecular species level.…”