Speciation and identification of tellurium-containing metabolites in garlic, Allium sativum

Abstract

Tellurium (Te) is a widely used metalloid in industry because of its unique chemical and physical properties. However, information about the biological and toxicological activities of Te in plants and animals is limited. Although Te is expected to be metabolized in organisms via the same pathway as sulfur and selenium (Se), no precise metabolic pathways are known in organisms, particularly in plants. To reveal the metabolic pathway of Te in plants, garlic, a well-known Se accumulator, was chosen as the model plant. Garlic was hydroponically cultivated and exposed to sodium tellurate, and Te-containing metabolites in the water extract of garlic leaves were identified using HPLC coupled with inductively coupled plasma mass spectrometry (ICP-MS) or electrospray tandem mass spectrometry (ESI-MS-MS). At least three Te-containing metabolites were detected using HPLC-ICP-MS, and two of them were subjected to HPLC-ESI-MS-MS for identification. The MS spectra obtained by ESI-MS-MS indicated that the metabolite was Te-methyltellurocysteine oxide (MeTeCysO). Then, MeTeCysO was chemically synthesized and its chromatographic behavior matched with that of the Te-containing metabolite in garlic. The other was assigned as cysteine S-methyltellurosulfide. These results suggest that garlic can assimilate tellurate, an inorganic Te compound, and tellurate is transformed into a Te-containing amino acid, the so-called telluroamino acid. This is the first report addressing that telluroamino acid is de novo synthesized in a higher plant.

Evaluation of selenium in dietary supplements using elemental speciation

“…The peak Unk-A initially thought to be SeCys 2 , was determined to be Se-methylselenocysteine oxide (MeSeOCys), and the peak Unk-B was determined to be methylseleninic acid (MSeA). Although the MS 2 of MeSeOCys does not provide much structural information, similar fragmentation was discussed in Anan et al (2013). For MSeA, the MS 2 spectra were consistent with the report by Gosetti et al (2007).…”

UPLC-Q-TOF/MS-based screening and identification of two major bioactive components and their metabolites in normal and CKD rat plasma, urine and feces after oral administration of Rehmannia glutinosa Libosch extract

“…When the LC-MS post-acquisition data files were processed using MetaboLynx TM , comparisons between the analyte and control samples were carried out according to the retention time, peak areas and MS spectra [30][31][32]. Based on the retention time, mass difference and spectral patterns of product ions, a series of probable metabolites were obtained using the UPLC-Q-TOF/MS technology with MS E data acquisition method.…”

The Biosynthesis of Infrared-Emitting Quantum Dots in Allium Fistulosum

“…Whilst there are few reports on tellurium metabolites in plants, Te -methyltellurocysteine oxide has been observed as the major metabolic species from the exposure of Allium sativum to Na 2 TeO 4 . Te -methyltellurocysteine oxide was further reported to degrade to either methyltellurol or methyltellurous acid, which was then sequestered by cysteine giving S -methyltellurylsulfide 17 . Assuming a similar reaction in Allium fistulosum , which of these metabolites is the actual tellurium precursor is at present unknown although methyltellurol has previously been reported as a precursor in the preparation of CdTe and HgCdTe thin films by chemical vapour deposition 18 .…”