Impact of Cr(VI) on the oxidation of polyunsaturated fatty acids in Helianthus annuus roots studied by metabolomic tools

• Published in: Chemosphere (Oxford) Vol. 220; pp. 442 - 451
• Main Authors: Gonzalez Ibarra, Alan Alexander, Wrobel, Katarzyna, Yanez Barrientos, Eunice, Corrales Escobosa, Alma Rosa, Gutierrez Corona, J. Felix, Enciso Donis, Israel, Wrobel, Kazimierz
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2019
• Subjects: Chromium(VI); Helianthus annuus; Liquid chromatography; Mass spectrometry; metabolomics; Oxylipins; Liquid chromatography; Helianthus annuus; Chromium(VI); metabolomics; Mass spectrometry; Oxylipins
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.12.145

The impact of Cr(VI) in sunflower roots has been studied, focusing on the oxidation of polyunsaturated fatty acids. Plants were grown hydroponically in the presence of 0, 1.0, 5.0 and 25 mgCr L−1. Methanolic root extracts were analyzed by capillary liquid chromatography coupled through negative electrospray ionization to a quadrupole-time of flight mass spectrometry (capHPLC-ESI-QTOF-MS). Using partial least squares algorithm, eighteen features strongly affected by Cr(VI) were detected and annotated as linoleic acid (LA), alpha-linolenic acid (ALA) and sixteen oxidation products containing hydroperoxy-, epoxy-, keto-, epoxyketo- or hydroxy-functionalities, all of them classified as oxylipins. Inspection of the MS/MS spectra acquired for features eluting at different retention times but assigned as a sole compound, confirmed isomers formation: three hydroperoxy-octadecadienoic acids (HpODE), two oxo-octadecadienoic acids (OxoODE) and four epoxyketo-octadecenoic acids (EKODE). Around 70% of metabolites in sunflower LA metabolic pathway were affected by Cr(VI) stress and additionally, four EKODE isomers not included in this pathway were found in the exposed roots. Among ALA-derived oxylipins, 13-epi-12-oxo-phytodienoic acid (OPDA) is of relevance, because of its participation in the activation of secondary metabolism. The abundances of all oxylipins were directly dependent on the Cr(VI) concentration in medium; furthermore, autooxidation of LA to HpODE isomers was observed after incubation with Cr(VI). These results point to the direct involvement of Cr(VI) in non-enzymatic oxidation of fatty acids; since oxylipins are signaling molecules important in plant defensive response, their synthesis under Cr(VI) exposure sustains the ability of sunflower to grow in Cr(VI)-contaminated environments. [Display omitted] •Cr(VI) impact in sunflower roots was studied by LC-MS-based metabolomic approach.•Statistical PLS method was used to find compounds mostly affected by Cr(VI).•Eighteen compounds were annotated as linoleic, linoleic acids and related oxylipins.•Direct involvement of Cr(VI) in non-enzymatic oxidation of fatty acids is proposed.•Oxylipins as signaling molecules participate in sunflower defense against Cr(VI).