Characterization of the selenocysteine-containing metabolome in selenium-rich yeast : Part 1. Identification of new species by multi-dimensional liquid chromatography with parallel ICP-MS and electrospray Q-TOFMS/MS detection

Abstract

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.

Selenopeptides and elemental selenium in Thunbergia alata after exposure to selenite: quantification method for elemental selenium

“…1A and Fig. 31,32 Induction of PC by selenium is rarely reported in plants except for those reported in yeast extracts 29,33 and in Rauvolfia serpentine. Its molecular structure was elucidated from the MS/MS fragmentation data (Fig.…”

“…1B) and 1D) with signals at m/z 488 (indicating loss of glycine), m/z 434 (indicating loss of glutamic acid) and at m/z 256 (indicating the loss of glutathione) helped to identify the selenopeptide as selenocysteinyl-2-3-dihydroxypropionyl-glutathione conjugate with the structure shown below ( Fig. The first elucidation of its structure in yeast extracts was made by Dernovics et al 29 and later its isomer selenoglutathione-N-2,3dihydroxypropionyl cysteine was identified by Preud'homme et al 30 also in selenized yeast. This species (m/z 562) with a Se-S bond between a glutathione molecule and a selenocysteinyl residue has been previously identified in selenized yeast extracts, 27,28 but its structure could not be assigned because of the limitation of the methods used.…”

Development of lc-ms methods for the analyses of selenium species of natural and of synthetic origin

“…Taking into account that almost 70 Se species have been identified from selenised yeast [17,178] and the fact that Se-yeast is the only natural (that is, not a synthetic compound based) and approved source for human selenium supplementation in the EU, the list of lacking (~ 60) selenium standards is more than remarkable. [142] and Goenega-Infante et al [179], while its structure was tentatively identified in 2008 based on high resolution ESI-MS data [97]. Since that time this compound has been detected and cited continuously from several producers and yeast strains [17,180,181].…”

“…and Figure 12c presents the MS/MS data (see also Table 11). Similarly to the fragmentation of the Se-containing glutathione family and selenocystine in positive ion mode [86,97], the intense fragments arrive from the loss of Gly, γ-Glu residues and neutral losses of NH 3 and HCOOH, while the S-Se bond is hardly fragmented and the intact glutathione and selenocysteine residues are only of low abundance.…”

“…Combining the optimized processes of selenocysteine-glutathione conjugation and the clean-up of 2,3-DHP-containing selenocystine species were the prerequisites to arrive at a detectable amount of 2,3-DHP-selenocysteine-glutathione. However, this compound is slightly retained on special RP-HPLC columns intended for use with eluents with low organic solvent content [179]; therefore, a more robust clean-up technique with SAX-HPLC was chosen [97].…”