How and do selenium supplements really work? Analytical scientists are helping to find the answer.

Selenium compounds such as methylseleninic acid have known anticancer activity, but the way they work is not well-understood. Now, UK scientists have used analytical methods to study how selenium compounds are metabolised in human cancer cell lines. 'These novel methods will be used in the context of clinical trials investigating selenium supplementation to identify the mechanisms by which selenium exerts its biological effects,' said Heidi Goenaga Infante, at the LGC in Teddington, who fronted the research.

Goenaga Infante and her colleagues used a combination of analytical techniques, including mass spectrometry and gas chromatography, to detect the selenium metabolites. To analyse the volatile metabolites, the team employed a technique called cryogenic oven-cooling gas chromatography, which involves cooling the apparatus rapidly down to temperatures as low as -60 ^oC. 'This method showed advantages in terms of cost and simplicity,' said Goenaga Infante.

The researchers found that Se-methylselenocysteine is the major selenium metabolite in lymphoma cell lines treated with methylseleninic acid. They have also reported the first mass spectrometry data for water soluble precursors of methylselenol - a metabolite with anticancer activity - and volatile methylated selenium species formed in the selenium-treated cells.

Peter Uden, a US expert in analytical science at the University of Massachusetts, Amherst, said, 'this is among the most innovative and valuable contributions to organoselenium speciation in recent years. Any elemental speciation, not solely for selenium, is accessible to this approach. The ability to sample small cellular samples is a substantial advance and the links between selenocysteine and cell metabolism are key findings.'

In the future, Goenaga Infante says, she hopes to develop methodologies for measuring and identifying analogous sulfur-containing biomolecules in biosamples.

Kathleen Too