For the first time, researchers from the Karl-Franzens-University (Graz, Austria) have determined methyl 2-acetamido-2-deoxy-1-seleno-ß-D-galactopyranoside (selenosugar 1), and methyl 2-amino-2-deoxy-1-seleno-ß-D-galactopyranoside in human serum by HPLC–ICPMS.
Background:Selenium is an essential micronutrient, but at high doses can be toxic, and as such interest in monitoring its status using biomarkers is of importance. In contrast to small selenium compounds present in urine, selenium in blood is mainly associated with large biomolecules such as selenoproteins traditionally determined with biochemical assays. Less attention has been paid to small “non-protein” selenium species in human blood. Up until now selenite, selenate and selenomethionine (SeMet) have been tentatively identified in human serum.
The recent failure of the SELECT trial to demonstrate that supplementation with SeMet reduces the incidence of prostate cancer has generated interest in small selenium species. The negative outcome from SELECT has been partly attributed by some researchers to the use of pure SeMet instead of selenized yeast as the selenium source and raised the possibility that other minor selenium constituents were responsible for the previously observed anticancer properties of selenized yeast.
The new study:The researchers from the Karl-Franzens-University integrated a protein precipitation step into their HPLC-ICP-MS-based method. The removal of “protein-bound” selenium and concomitant concentration of the small selenium species prior to quantitative determination by HPLC-ICP-MS provided a "cleaner matrix" and consequently, sub-µg selenium per liter level quantification limits. Furthermore, high recoveries of 73-103% were obtained during spiking experiments with some small Se-species, except for selenite, which had a low recovery of 44% that was attributed to "protein binding”. After such validation, native serum samples from two volunteers before and after ingestion of a selenium food supplement containing selenate were investigated.
methyl-2-acetamido-2-deoxy-
1-seleno-ß-D-galactopyranoside
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methyl-2-amino-2-deoxy-
1-seleno-ß-D-galactopyranoside
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Results showed the presence of methyl 2-acetamido-2-deoxy-1-seleno-ß-d: -galactopyranoside and trace amounts of methylseleno-cysteine and methyl 2-amino-2-deoxy-1-seleno-ß-d: -galactopyranoside, which have not been reported in human serum before.
The original study
Sabine Kokarnig,
Doris Kuehnelt, Michael Stiboller, Ulrike Hartleb,
Kevin A. Francesconi,
Quantitative determination of small selenium species in human serum by HPLC/ICPMS following a protein-removal, pre-concentration procedure, Anal. Bioanal. Chem., 400 (2011) 2323–2327.
DOI 10.1007/s00216-011-4992-5 Related studies Liang Hu, Ze-Qin Dong, Xiao-Han Huang, Yu-Feng Li, Bai Li, Li-Ya Qu, Guo-Ping Wang, Yu-Xi Gao, Chun-Ying Chen,
Analysis of Small Molecular Selenium Species in Serum Samples from Mercury-Exposed People Supplemented With Selenium-Enriched Yeast by Anion Exchange-Inductively Coupled Plasma Mass Spectrometry, Chin. J. Anal. Chem., 39/4 (2011)466–470.
DOI: 10.1016/S1872-2040(10)60432-X Petru Jitaru,
Heidi Goenaga-Infante, Sophie Vaslin-Reimann, Paola
Fisicaro,
A systematic approach to the accurate quanti?cation of
selenium in serum selenoalbumin by HPLC–ICP-MS, Analytica Chimica Acta ,
657 (2010) 100–107.
doi:10.1016/j.aca.2009.10.037 Petru Jitaru, Marco Roman, Giulio Cozzi, Paola Fisicaro, Paolo
Cescon,
Carlo Barbante,
Speciation analysis of selenoproteins in human
serum by microbore affinity-HPLC hyphenated to ICP-Sector field-MS
using a high efficiency sample introduction system, Microchim. Acta, 166
(2009) 319–327.
DOI 10.1007/s00604-009-0208-5 Petru Jitaru, Giulio Cozzi, Andrea Gambaro, Paolo Cescon,
Carlo
Barbante,
Simultaneous speciation analysis of glutathione peroxidase selenoprotein
P and selenoalbumin in human serum by tandem anion exchange-affinity
HPLC and on-line isotope dilution ICP-quadrupole MS, Anal. Bioanal.
Chem., 391 (2008) 661–669.
DOI 10.1007/s00216-008-2043-7 Petru Jitaru, Marco Prete, Giulio Cozzi, Clara Turetta, Warren Cairns, Roberta
Seraglia, Pietro Traldi, Paolo Cesconac,
Carlo Barbante,
Speciation
analysis of selenoproteins in human serum by solid-phase extraction and affinity HPLC hyphenated to ICP-quadrupole MS, J. Anal. At. Spectrom., 23 (2008) 402–406.
DOI: 10.1039/b712693j O. Palacios, J.R. Encinar,
D. Schaumlöffel,
R. Lobinski,
Fractionation
of selenium-containing proteins in serum by multiaffinity liquid
chromatography before size-exclusion chromatography–ICPMS, Anal. Bioanal. Chem., 384 (2006) 1276–1283.
doi: 10.1007/s00216-005-0286-0 L. Hinojosa Reyes,
J.M. Marchante-Gayon, J.I. Garcia Alonso,
A. Sanz-Medel,
Quantitative speciation of selenium in human serum by affinity chromatography coupled to post-column isotope dilution analysis ICP-MS, J. Anal. At. Spectrom., 18 (2003) 1210–1216.
doi: 10.1039/b305455a
Related EVISA Resources Brief Summary: LC-ICP-MS: The most often used hyphenated system for speciation analysis Link database: Protein-bound selenium and human health Link Database: Toxicity of selenium
Related News July 20, 009: Researchers Reveal Selenium's Metabolism In Life-Giving Amino Acids October 28, 2008: National Cancer Institute ends Selenium and Vitamin E Cancer Prevention Trial, or SELECT March 16, 2008: New selenium-containing proteins identified in selenium-rich yeast April 9, 2007: Trimethylselenonium is not the major metabolite
for human cancer patients excreting high doses of selenium October 16, 2005: New light on human selenium metabolism October 6, 2005: Selenomethionine shows promising results as a protective agent against Esophageal Cancer August 2, 2005: New CRM for Selenomethionine in yeast developed by NRC Canada is now on the market March 8, 2005: Selenoprotein P is required for normal sperm developmentlast time modified: August 9, 2011
