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.

Different tacrolimus epoxides and dihydrodiol epoxides arising from the chemical oxidation of the parent drug are described. Open-chain tautomeric forms involving the lactone function were identified for the tacrolimus epoxides. Moreover, the identification by electrospray and electrospray linked scan mass spectrometry of an SDZ-RAD C16-C27 O-demethyl 17, 18-19, 20-21, 22 tris-epoxide new metabolite isolated from pig liver microsomes is reported.

Isolation from rat urine and human liver microsomes and identification by electrospray and nanospray tandem mass spectrometry of new malagashanine metabolites.

Malagashanine has been isolated from indigenous madagascan Strychnos myrtoides alkaloids used traditionally to treat malaria. This alkaloid was found to enhance the action of chloroquine against chloroquine-resistant strains of Plasmodium falciparum when combined with classical antimalarial drugs (chloroquine, quinine). The present study was carried out in order to investigate by electrospray mass and tandem mass spectrometry and NMR spectroscopy the structure of two new metabolites isolated from rat urine and human liver microsomes.

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.

Macrolide immunosuppressive drugs such as tacrolimus (FK506) and sirolimus (rapamycin) are compounds largely used in modern immunosuppressive therapy and considered as powerful immunosuppressive agents. Some of these molecules are still under clinical development as, for example, SDZ-RAD (40-O-(2-hydroxyethyl)rapamycin), an immunosuppressive drug closely related to rapamycin. SDZ-RAD has a molecular mass of 957.

Isolation, identification and immunosuppressive activity of SDZ-IMM-125 metabolites from human liver microsomes.

SDZ-IMM-125 N-methyl leucine 9 hydroxylated in the gamma position is a metabolite which was extracted from incubated human liver microsomes and subsequently separated by normal and reverse-phase HPLC. This metabolite was identified by fast atom bombardment mass spectrometry, electrospray-ms/ms mass spectrometry and nuclear magnetic resonance spectroscopy. The in vitro 50% inhibitory concentration, tested against bidirectional mixed lymphocyte reaction was 80 microg/l indicating that this metabolite does not retain in vitro immunosuppressive activity most probably due to the structural modification of SDZ-IMM-125 in the recognized binding region to cyclophilin A reducing its binding affinity relative to the parent drug.

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

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.