Characterization of the selenocysteine-containing metabolome in selenium-rich yeast

Size-exclusion chromatography (SEC)-strong anion-exchange (SAX) HPLC fractionation of selenium species from the aqueous extract of a selenised yeast sample was optimised under the strict selenium mass balance control by ICP-MS. The SAX HPLC-ICP-MS chromatogram of the most intense SEC fraction produced seven peaks. They were all successfully identified by reversed phase (RP) nanoHPLC-electrospray Q-TOFMS/MS. Eight Se-compounds (derivatives of glutathione) were identified: six of them have not been reported previously. Six of the identified compounds contained selenocysteine (28% of the water-soluble selenium), stabilised by either Se-S or Se-Se bridges. The extensive MS/MS data presented are potentially useful for the optimization of direct LC-ESIMS/MS analyses in the selected (SRM) or multiple (MRM) reaction monitoring modes for the purpose of the authenticity and quality control of Se-rich yeast supplements.