Identification of a novel selenium metabolite, Se-methyl-N-acetylselenohexosamine, in rat urine by high-performance liquid chromatography-inductively coupled plasma mass spectrometry and -electrospray ionization tandem mass spectrometry

The major urinary metabolite of selenium Se) in rats was identified by HPLC-inductively coupled argon plasma mass spectrometry (ICP-MS) and -electrospray tandem mass spectrometry (ESI-MS/MS). As the urine sample was rich in matrices such as sodium chloride and urea, it was partially purified to meet the requirements for ESI-MS. The group of signals corresponding to the So isotope ratio was detected in both the positive and negative ion modes at m/z 300 ([M+H](+)) and 358 ([M+CH3COO](-)) for Se-80, respectively. These results suggested that the molecular mass of the Se metabolite was 299 Da for Se-80. The Se metabolite was deduced to contain one methylselenyl group, one acetyl group and at least two hydroxyl groups from the mass spectra of the fragment ions. The spectrum of the So metabolite was completely identical to that of the synthetic selenosugar, 2-acetamide-1,2-dideoxy-beta-D-glucopyranosyl methylselenide. However, the chromatographic behavior of the Se metabolite was slightly different from that of the synthetic selenosugar. Thus, the major urinary Se metabolite was assigned as a diastereomer of a selenosugar, Se-methyl-N-acetyl-selenohexosamine. (C) 2002 Elsevier Science B.V. All rights reserved.