Isolation, purification and structure elucidation of cyclosporin A metabolites in rabbit and man.

Metabolism of cyclosporin A (CsA) was studied in a model of isolated and perfused rabbit liver, and in man. After diethyl ether extraction, CsA metabolites were separated and successfully purified by a combination of two high-performance liquid chromatographic (HPLC) procedures. A normal-phase HPLC methodology was used to separate most of the metabolites, and further separation and purification were optimized with a reversed-phase HPLC method. 27 different CsA metabolites were separated, collected, and characterized by fast atom bombardment mass spectrometry. In addition to several metabolites already described (OL-1, OL-17, OL-18 and OL-21), new compounds (of original molecular weights 1236, 1222 and 1174, and numerous structural isomers of previously reported molecular weights) were isolated from rabbit and human bile. Mass spectral analysis of two of these new metabolites strongly suggests vicinal dihydrodiol (mol. wt 1236) and N-demethylated vicinal dihydrodiol (mol. wt 1222) structures. These two new metabolites most probably derive from an epoxide as a preliminary intermediate

Gas chromatographic and mass fragmentographic assays of carcinogenic polycyclic hydrocarbon epoxide hydratase activity.

A specific and very sensitive procedure for the determination of epoxide hydratase activity in hepatic microsomes is described. Any polycyclic hydrocarbon epoxide can be used as a substrate; in this study, benzo(a)anthracene-5,6-oxide, benzo(a)pyrene-4,5-oxide and 3-methylcholanthrene-11,12-oxide were utilized. The corresponding trans-diols formed during incubation are separated and evaluated using either an electron-capture gas chromatographic method for the determination of their chloromethyldimethylsilylated derivatives or gas chromatographic-mass fragmentographic measurement of their trimethylsilylated derivatives. Concentrations as low as 1 ng per millilitre of incubation mixture can be estimated

Isolation and mass spectrometric identification of five metabolites of FK-506, a novel macrolide immunosuppressive agent, from human plasma.

The isolation and mass spectrometric identification of several metabolites of FK-506 from human plasma are described