Oxidative production of monomethylated selenium from the major urinary selenometabolite, selenosugar

In addition to the major urinary selenometabolite, 1β-methylseleno-N-acetyl-D-galactosamine (selenosugar), several minor selenometabolites were also detected in rat urine by high performance liquid chromatography–inductively coupled argon plasma mass spectrometry. One of them, in a partially purified urine sample, was generated from selenosugar under aerobic conditions and also transformed through oxidation by H2O2. It was identified as monomethylseleninic acid. Therefore, this urinary selenocompound should not be regarded as a naturally occurring metabolite but as a selenosugar artifact. Moreover, an additional selenometabolite was detected in the same urine sample. Although this selenometabolite has not been identified yet, it seems to contain monomethylselenyl group(s) because of its transformation to monomethylseleninic acid through oxidation. Thus, urine samples must be handled with care so as not to allow oxidation by air, to prevent transformation to artificial selenocompounds.