Ferrioxamine and its hexadentate iron-chelating metabolites in human post-desferal urine studied by high-performance liquid chromatography and fast atom bombardment mass spectrometry.

Three iron-containing fractions were detected by high-performance liquid chromatography (HPLC) on a reverse-phase column in the 24-h urine of two patients with hereditary hemochromatosis following the injection of deferoxamine mesylate (Desferal). These fractions have virtually identical absorption spectra in the visible range, with a broad maximum around 430 nm. Molecular weight determination of these fractions was performed by fast atom bombardment mass spectrometry (FAB-MS), which gave intense ion signals for the protonated molecular ions of the intact iron chelates, namely, at m/z 614 for ferrioxamine (FOA; Mr 613), at m/z 629 for metabolite I (FOA-MI; Mr 628), and at m/z 601 for metabolite II (FOA-MII; Mr 600). The molecular weight of FOA-MI is compatible with deamination of the terminal amino function and oxidation of the adjacent carbon atom to a carboxyl group; the molecular weight of FOA-MII is compatible with loss of a C2H4 unit from FOA-MI by beta oxidation. Quantification of iron in post-Desferal urine samples either by atomic absorption spectrometry (AAS) or by HPLC leads to results which are identical within experimental error. In ten subsequent 12-h urine samples of a patient under therapy (subcutaneous infusion of Desferal), the following distribution of urinary iron was found: FOA-MI, 58.4 +/- 4.7% (arithmetic mean +/- SD); FOA, 33.2 +/- 4.9%; FOA-MII, 8.4 +/- 1.7%. Addition of 2 mM ethylenediaminetetraacetic acid (EDTA) to the chromatographic solvents was used as a stability test for FOA and its two metabolites MI and MII.(ABSTRACT TRUNCATED AT 250 WORDS)