Water-soluble organic selenometabolites of alfalfa (Medicago sativa L.) green biomass-derived fractions

• Published in: Journal of trace elements in medicine and biology 2024-12, Vol.86, p.127545, Article 127545
• Main Authors: Domokos‑Szabolcsy, Éva, Soós, Áron, Kovács, Béla, Kovács, Zoltán, Dernovics, Mihály
• Format: Article
• Language: English
• Subjects: Biomass; ESI-QTOF-MS; ICP-MS; Lucerne; Mass Spectrometry; Medicago sativa - chemistry; Selenium - analysis; Selenium - chemistry; Selenium - metabolism; Selenium speciation; Selenosugar; Solubility; Water - chemistry; Yeast selenium metabolism
• ISSN: 0946-672X; 1878-3252; 1878-3252
• DOI: 10.1016/j.jtemb.2024.127545

Tolerance of plants towards selenium, a non-essential microelement for higher plants, is a key issue when designing either the indirect (selenium-depletion from highly seleniferous soils) or directed (selenized feed production) enrichment of selenium in forages. Alfalfa (Medicago sativa L.), the well-known forage crop of the Fabaceae family, has been gaining considerable interest due to its application as a green manure, as a cover crop, or in soil remediation by nitrogen fixation. The goal of our study was to assess into which selenocompounds alfalfa plants biotransform the excess selenium uptake from the soil. Selenocompounds (other than selenomethionine and inorganic forms) accumulated in the fiber and the so-called brown juice by-product fractions of processed alfalfa biomass were targeted. Inductively coupled plasma – mass spectrometry assisted multidimensional (strong anion exchange, strong cation exchange, reversed phase) orthogonal chromatographic purification was applied to supply Se-containing fractions in adequately high purity for electrospray high-resolution mass spectrometry (used for the first time for this matrix) analyses. As a total, 30 selenocompounds (with isomers) were described, showing the abundance of the derivatives of selenohexose, selenohomolanthionine, and 2,3-dihydroxypropionic acid. Out of the 30 selenocompounds, 15 could be assigned the elemental composition, and the tentative structure of five compounds including among others deamino-2-oxo-selenohomolanthionine, deamino-hydroxy-selenohomolanthionine, and the dimer of 2,3-dihydroxypropionyl-selenohomocysteine could be presented. The studied fractions arising from the standard alfalfa processing technology contained a wide variety of selenocompounds whose origin can be either the plant’s inherent Se metabolism or the processing technology itself. The importance of negative mode data acquisition has been highlighted, as out of the 30 compounds, 16 could be detected exclusively in this electrospray ionization mode. •Tolerance of alfalfa against selenium in selenite-containing soil is described.•30 selenocompounds detected with multidimensional LC-ICP-MS/ESI-HRMS setups.•Derivatives of selenohomolanthionine and 2,3-dihydroxypropionic acid are assigned.•Selenocompound formerly reported in yeast selenometabolism detected now in alfalfa.•Tentative assignment of 18 selenosugars (with isomers) presented.