@article{KroepflMarschallFrancesconietal.2017,
  author    = {Kr{\"o}pfl, Nina and Marschall, Talke A. and Francesconi, Kevin A. and Schwerdtle, Tanja and Kuehnelt, Doris},
  title     = {Quantitative determination of the sulfur-containing antioxidant ergothioneine by HPLC/ICP- QQQ-MS},
  series = {Journal of Analytical Atomic Spectrometry},
  volume    = {32},
  journal   = {Journal of Analytical Atomic Spectrometry},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {0267-9477},
  doi       = {10.1039/c7ja00030h},
  pages     = {1571 -- 1581},
  year      = {2017},
  abstract  = {Interest in the sulfur-containing antioxidant ergothioneine calls for reliable analytical methods for its quantification. In this work, a method based on reversed-phase high performance liquid chromatography (RP-HPLC) coupled with elemental mass spectrometry detection in mass shift mode (inductively coupled plasma triple quadrupole mass spectrometry, ICP-QQQ-MS) using oxygen as the reaction gas was developed for the element-selective determination of ergothioneine in complex biological matrices. Application of an instrumental setup using a 6-port-valve and the introduction of a methanol gradient allowed the time-efficient analysis of samples containing strongly retained sulfur species besides ergothioneine without compromising ICPMS detection. In aqueous solution, limits of detection and quantification (LOD and LOQ) of the optimized method for m/z 32 -> 48 (SO+) were 0.23 mu g S per L and 0.80 mu g S per L, respectively; measurements in a complex matrix (human hepatocyte carcinoma cells, HepG2) resulted in an LOD of 0.6 mu g S per L and an LOQ of 2.3 mu g S per L. Recoveries of ergothioneine from cell pellets spiked with the analyte before cell lysis (97 +/- 3\%) matched those obtained for cell culture medium spiked before syringe filtration (96 +/- 9\%) demonstrating that sample preparation did not impair the quantitative determination of ergothioneine. When HepG2 cells were exposed to ergothioneine via the culture medium, they showed low absorption; approximately 3\% of the added ergothioneine was found in cell lysates, while most of it (>= 85\%) remained in the cell culture medium. The method is capable of separating ergothioneine from other biologically relevant sulfur-containing species and is expected to be of broad future use. Furthermore, the potential use for the simultaneous separation of selenium species, thereby extending the scope of possible applications, was demonstrated by applying it to water extracts of oyster mushrooms.},
  language  = {en}
}
@article{RohnMarschallKroepfletal.2018,
  author    = {Rohn, Isabelle and Marschall, Talke Anu and Kr{\"o}pfl, Nina and Jensen, Kenneth Bendix and Aschner, Michael and Tuck, Simon and Kuehnelt, Doris and Schwerdtle, Tanja and Bornhorst, Julia},
  title     = {Selenium species-dependent toxicity, bioavailability and metabolic transformations in Caenorhabditis elegans},
  series = {Metallomics : integrated biometal science},
  volume    = {10},
  journal   = {Metallomics : integrated biometal science},
  number    = {6},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1756-5901},
  doi       = {10.1039/c8mt00066b},
  pages     = {818 -- 827},
  year      = {2018},
  abstract  = {The essential micronutrient selenium (Se) is required for various systemic functions, but its beneficial range is narrow and overexposure may result in adverse health effects. Additionally, the chemical form of the ingested selenium contributes crucially to its health effects. While small Se species play a major role in Se metabolism, their toxicological effects, bioavailability and metabolic transformations following elevated uptake are poorly understood. Utilizing the tractable invertebrate Caenorhabditis elegans allowed for an alternative approach to study species-specific characteristics of organic and inorganic Se forms in vivo, revealing remarkable species-dependent differences in the toxicity and bioavailability of selenite, selenomethionine (SeMet) and Se-methylselenocysteine (MeSeCys). An inverse relationship was found between toxicity and bioavailability of the Se species, with the organic species displaying a higher bioavailability than the inorganic form, yet being less toxic. Quantitative Se speciation analysis with HPLC/mass spectrometry revealed a partial metabolism of SeMet and MeSeCys. In SeMet exposed worms, identified metabolites were Se-adenosylselenomethionine (AdoSeMet) and Se-adenosylselenohomocysteine (AdoSeHcy), while worms exposed to MeSeCys produced Se-methylselenoglutathione (MeSeGSH) and -glutamyl-MeSeCys (-Glu-MeSeCys). Moreover, the possible role of the sole selenoprotein in the nematode, thioredoxin reductase-1 (TrxR-1), was studied comparing wildtype and trxr-1 deletion mutants. Although a lower basal Se level was detected in trxr-1 mutants, Se toxicity and bioavailability following acute exposure was indistinguishable from wildtype worms. Altogether, the current study demonstrates the suitability of C. elegans as a model for Se species dependent toxicity and metabolism, while further research is needed to elucidate TrxR-1 function in the nematode.},
  language  = {en}
}