Latvian State Institute of Wood Chemistry, Dzerbenes Str. 27, LV-1006 Riga, Latvia.
INSERM UMR 1248, Université de Limoges, Faculté de Pharmacie, 2 rue du Docteur Marcland, 87025 Limoges Cedex, France.
Molecules. 2019 May 9;24(9):1794. doi: 10.3390/molecules24091794.
The valorization of lignins as renewable aromatic feedstock is of utmost importance in terms of the use of sustainable resources. This study provides a deductive approach towards market-oriented lignin-derived antioxidants by ascertaining the direct effect of different structural features of lignin on the reactivity of its phenolic OH groups in the radical scavenging reactions. The antioxidant activity of a series of compounds, modeling lignin structural units, was experimentally characterized and rationalized, using thermodynamic descriptors. The calculated O-H bond dissociation enthalpies (BDE) of characteristic lignin subunits were used to predict the modification pathways of technical lignins. The last ones were isolated by soda delignification from different biomass sources and their oligomeric fractions were studied as a raw material for modification and production of optimized antioxidants. These were characterized in terms of chemical structure, molecular weight distribution, content of the functional groups, and the antioxidant activity. The developed approach for the targeted modification of lignins allowed the products competitive with two commercial synthetic phenolic antioxidants in both free radical scavenging and stabilization of thermooxidative destruction of polyurethane films.
木质素作为可再生芳香族原料的增值在利用可持续资源方面具有重要意义。本研究通过确定木质素不同结构特征对其酚羟基在自由基清除反应中的反应性的直接影响，提供了一种针对市场的木质素衍生抗氧化剂的演绎方法。使用热力学描述符，对一系列模拟木质素结构单元的化合物的抗氧化活性进行了实验表征和合理化。木质素特征亚基的计算 O-H 键离解焓 (BDE) 用于预测技术木质素的修饰途径。这些木质素是通过苏打制浆从不同生物质来源分离得到的，其低聚物级分被用作修饰和生产优化抗氧化剂的原料。这些抗氧化剂的化学结构、分子量分布、官能团含量和抗氧化活性都进行了研究。针对木质素的目标修饰的开发方法使产品在自由基清除和稳定聚氨酯薄膜的热氧化降解方面具有竞争力，可与两种商业合成酚类抗氧化剂相媲美。
