Dearomatization drives complexity generation in freshwater organic matter

作者：Siyu Li, Mourad Harir, David Bastviken, Philippe Schmitt‐Kopplin, Michael Gonsior, Alex Enrich-Prast, Juliana Valle, Norbert Hertkorn · 发表于：Nature · 年份：2024 · DOI：10.1038/s41586-024-07210-9 · 被引用次数：50 · 研究领域：Metabolomics and Mass Spectrometry Studies、Molecular spectroscopy and chirality、Marine and coastal ecosystems

Abstract Dissolved organic matter (DOM) is one of the most complex, dynamic and abundant sources of organic carbon, but its chemical reactivity remains uncertain 1–3 . Greater insights into DOM structural features could facilitate understanding its synthesis, turnover and processing in the global carbon cycle 4,5 . Here we use complementary multiplicity-edited 13 C nuclear magnetic resonance (NMR) spectra to quantify key substructures assembling the carbon skeletons of DOM from four main Amazon rivers and two mid-size Swedish boreal lakes. We find that one type of reaction mechanism, oxidative dearomatization (ODA), widely used in organic synthetic chemistry to create natural product scaffolds 6–10 , is probably a key driver for generating structural diversity during processing of DOM that are rich in suitable polyphenolic precursor molecules. Our data suggest a high abundance of tetrahedral quaternary carbons bound to one oxygen and three carbon atoms (OC q C 3 units). These units are rare in common biomolecules but could be readily produced by ODA of lignin-derived and tannin-derived polyphenols. Tautomerization of (poly)phenols by ODA creates non-planar cyclohexadienones, which are subject to immediate and parallel cycloadditions. This combination leads to a proliferation of structural diversity of DOM compounds from early stages of DOM processing, with an increase in oxygenated aliphatic structures. Overall, we propose that ODA is a key reaction mechanism for complexity a...