Data_Sheet_1_Nano-Sized Antioxidative Trimetallic Complex Based on Maillard Reaction Improves the Mineral Nutrients of Apple (Malus domestica Borkh.).docx

The metallic complex is widely used in agricultural applications. Due to the oxidation of the metal and environmental unfriendliness of ligand, maintaining an efficient mineral supply for plants without causing environmental damage is difficult. Herein, an antioxidative trimetallic complex with high stability was synthesized by interacting Ca2+, Fe2+, and Zn2+ with the biocompatible ligands from the Maillard reaction. The composite structure elucidation was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR). Thermal stability was measured by thermogravimetric (TG). Antioxidative activities were evaluated by ferric reducing antioxidant power and radical scavenging activity assays. The three metals were successfully fabricated on the Maillard reaction products (MRPs) with contents of Ca (9.01%), Fe (8.25%), and Zn (9.67%). Microscopy images revealed that the three metals were uniformly distributed on the MRPs with partial aggregation of <30 nm. FTIR and XPS results revealed that the metals were interacted with MRPs by metal–O and metal–N bonds. TG and antioxidative activity assays showed that the trimetallic complex meets the requirements of thermodynamics and oxidation resistance of horticultural applications. Additionally, the results of the exogenous spraying experiment showed that the trimetallic complex significantly increased the mineral contents of the “Fuji” apple. By treatment with the complex, the concentrations of Ca, Fe, and Zn were increased by 85.4, 532.5, and 931.1% in the leaf; 16.0, 225.2, and 468.6% in the peel; and 117.6, 217.9, and 19.5% in the flesh, respectively. The MRP-based complexes offered a higher growth rate of the mineral content in apples than ones based on sugars or amino acids. The results of the spraying experiment carried out in 2 years show that the method has high reproducibility. This study thus promotes the development of green metallic complexes and expands the scope of agrochemical strategy.

该金属配合物在农业领域应用广泛。但由于金属易发生氧化反应、配体存在环境不友好性问题，难以在不对环境造成破坏的前提下为植物提供高效的矿物养分供给。本研究通过将钙离子（Ca²+）、亚铁离子（Fe²+）与锌离子（Zn²+）与美拉德反应（Maillard Reaction）生成的生物相容性配体进行配位，合成了一种高稳定性的抗氧化三金属配合物。采用透射电子显微镜（Transmission Electron Microscopy, TEM）、扫描电子显微镜（Scanning Electron Microscopy, SEM）、X射线光电子能谱（X-ray Photoelectron Spectroscopy, XPS）以及傅里叶变换红外光谱（Fourier Transform Infrared, FTIR）对该复合结构进行了表征。通过热重分析（Thermogravimetric, TG）测试了其热稳定性。采用铁离子还原抗氧化能力法与自由基清除活性实验评估了其抗氧化活性。成功将三种金属负载于美拉德反应产物（Maillard Reaction Products, MRPs）之上，三种金属的负载量分别为钙（Ca）9.01%、铁（Fe）8.25%以及锌（Zn）9.67%。显微成像结果显示，三种金属在MRPs上分布均匀，仅存在少量粒径小于30 nm的团聚体。傅里叶变换红外光谱与X射线光电子能谱结果表明，金属通过金属-氧键与金属-氮键与MRPs实现配位结合。热重分析与抗氧化活性实验结果表明，该三金属配合物满足园艺应用的热稳定性与抗氧化性能要求。此外，外源喷施实验结果显示，该三金属配合物可显著提升"富士"苹果的矿物养分含量。经该配合物处理后，苹果叶片中的钙、铁、锌浓度分别提升了85.4%、532.5%与931.1%；果皮中分别提升了16.0%、225.2%与468.6%；果肉中分别提升了117.6%、217.9%与19.5%。相较于以糖类或氨基酸为配体的配合物，基于MRPs的配合物可使苹果中矿物养分含量获得更高的增幅。为期两年的喷施实验结果表明，该方法具有良好的重现性。综上，本研究推动了绿色金属配合物的发展，并拓展了农用化学品策略的应用范围。