Selenium transformation studies during Broccoli (Brassica oleracea) growing process by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS)

Selenium uptake and transformation was studied in Se-enriched Broccoli (Brassica olearacea). Plants were grown in hydroponic culture and exposed during 40 days to Na2SeO3 (1 mg L-1). After growing, the plants were harvested and their different parts (roots, stems and fruit) were analyzed by ICP-MS or LC-ICP-MS. Se-species were identified and quantified after enzymatic extraction by using both an anion exchange (PRP-X100), and a size exclusion/ion exchange (Shodex Asahipak) chromatographic columns. Selenium translocation and transformation Se species in plants was studied through the Se-speciation in root, stem and fruit. After 40 days of exposure, selenomethionine was the major species found in roots, however, Semethylselenocysteine was the main species found in the fruit, suggesting Broccoli as a source of this important selenoamino acid in human diet. However, the degree of meal processing influences the stability of Se-aminoacids. Speciation studies in boiled Broccoli and in the extraction water were also carried out. This experiment revealed a noticeable degradation of Se-methylselenocysteine in the boiled Broccoli fruit. Proteins soluble in Tris-HCl were analyzed by two-dimensional chromatography coupled to ICP-MS. The results obtained contribute not only to a deeper understanding of Se accumulation mechanisms by plants but also to further functional food complements preparation and the effect of food processing on species stability. (c) 2007 Published by Elsevier B.V.