Department of Pharmaceutical Science, University of Salerno, Via Giovanni Paolo II, 84084, Fisciano (SA), Italy.
Phys Chem Chem Phys. 2018 Jun 27;20(25):17132-17140. doi: 10.1039/c8cp01893f.
Furan derivatives, potentially carcinogenic to humans, can be formed, in addition to carbohydrates and other sources, from the degradation of ascorbic acid (AA). At present, the mechanisms involved in the ascorbic acid degradation are not yet fully understood. In this study, we reported a gas-phase investigation, performed using Triple Quadrupole (TQ/MS) and Ion Trap Mass Spectrometry (QIT/MS) together with quantum mechanical calculations at the B3LYP/6-31+G(d,p) level of theory, on the non-oxidative degradation mechanism of l-ascorbic acid (AA) to furan derivatives. Gaseous protonated ascorbic acid ions, the AAH+ ionic reagents, were generated by Electrospray Ionization (ESI) of an aqueous AA solution added with a mild protonation reagent. The Collisionally Induced Dissociation (CID) mass spectra of the AAH+ ions displayed gaseous fragment ions corresponding to the degradation intermediates and reaction products, which were structurally characterized and identified. Precise mechanistic insights were achieved by using l-[1-13C]-AA. On the basis of experimental and computational results, the gas phase non-oxidative acid catalyzed degradation mechanism of ascorbic acid is proposed, a benchmark point for the comprehension of the mechanism in the condensed phase.
呋喃衍生物具有潜在的致癌性，除了碳水化合物和其他来源外，还可以由抗坏血酸（AA）的降解形成。目前，AA 降解的相关机制尚未完全清楚。在本研究中，我们报道了一项使用三重四极杆（TQ/MS）和离子阱质谱（QIT/MS）结合 B3LYP/6-31+G(d,p)理论水平的量子力学计算，对 L-抗坏血酸（AA）向呋喃衍生物非氧化降解机制的气相研究。通过向添加温和质子化试剂的 AA 水溶液进行电喷雾电离（ESI），生成气态质子化 AA 离子，即 AAH+离子试剂。AAH+离子的碰撞诱导解离（CID）质谱显示出与降解中间体和反应产物相对应的气态碎片离子，对其进行了结构表征和鉴定。使用 l-[1-13C]-AA 获得了精确的机制见解。基于实验和计算结果，提出了 AA 的气相非氧化酸催化降解机制，为理解凝聚相机制提供了基准点。
