德国环境与健康研究中心Hertkorn, Norbert团队报道了脱芳化驱动淡水有机质复杂性的产生。相关研究成果于2024年4月24日发表在国际顶尖学术期刊《自然》。

溶解有机物（DOM）是最复杂、最动态、最丰富的有机碳来源之一，但其化学反应性仍不确定。对DOM结构特征的深入了解有助于理解其在全球碳循环中的合成、循环和加工。

该文中，研究人员用互补多重编辑的¹³C核磁共振（NMR）光谱来量化，四条主要亚马逊河和两个中等大小的瑞典北方湖泊的DOM碳骨架的关键亚结构。研究发现，氧化脱芳（ODA）反应机制广泛用于有机合成化学中创建天然产物支架，可能是富含合适的多酚前体分子DOM加工过程中产生结构多样性的关键驱动因素。

研究数据表明，与一个氧和三个碳原子（OC_qC₃单元）结合的四面体季碳丰度很高。这些单元在常见的生物分子中很少见，但很容易通过木质素衍生的和单宁衍生的多酚的ODA产生。ODA对（聚）酚的互变异构化产生非平面环己二烯酮，其受到直接和平行的环加成作用。这种组合导致DOM加工早期阶段DOM化合物的结构多样性激增，含氧脂肪族结构增加。

总的来说，研究认为ODA是DOM分子加工过程中复杂性加速、新的含氧脂族分子产生的关键反应机制，并且它可能在自然界中普遍存在。使用互补多重编辑的¹³C核磁共振谱证明，氧化脱芳构化是溶解有机物处理过程中产生结构多样性的关键驱动因素，数据还表明OCqC3单元的丰度很高。

附：英文原文

Title: Dearomatization drives complexity generation in freshwater organic matter

Author: Li, Siyu, Harir, Mourad, Bastviken, David, Schmitt-Kopplin, Philippe, Gonsior, Michael, Enrich-Prast, Alex, Valle, Juliana, Hertkorn, Norbert

Issue&Volume: 2024-04-24

Abstract: Dissolved organic matter (DOM) is one of the most complex, dynamic and abundant sources of organic carbon, but its chemical reactivity remains uncertain1–3. Greater insights into DOM structural features could facilitate understanding its synthesis, turnover and processing in the global carbon cycle4,5. Here we use complementary multiplicity-edited 13C 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 scaffolds6–10, 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 (OCqC3 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 acceleration in the processing of DOM molecules, creation of new oxygenated aliphatic molecules and that it could be prevalent in nature. Using complementary multiplicity-edited 13C nuclear magnetic resonance spectra, oxidative dearomatization is shown to be a key driver for generating structural diversity during processing of dissolved organic matter and the data also suggest high abundance of OCqC3 units.

DOI: 10.1038/s41586-024-07210-9

Source: https://www.nature.com/articles/s41586-024-07210-9