Department of Bioproducts and Biosystems, School of Chemical Engineering , Aalto University , Post Office Box 16300, FI-00076 Aalto , Finland.
Department of Biochemistry and United States Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute , University of Wisconsin-Madison , Madison , Wisconsin 53726 , United States.
J Agric Food Chem. 2018 Jul 18;66(28):7294-7300. doi: 10.1021/acs.jafc.8b02014. Epub 2018 Jul 3.
Understanding the chemical structure of lignin in willow bark is an indispensable step to design how to separate its fiber bundles. The whole cell wall and enzyme lignin preparations sequentially isolated from ball-milled bark, inner bark, and wood were comparatively investigated by nuclear magnetic resonance (NMR) spectroscopy and three classical degradative methods, i.e., alkaline nitrobenzene oxidation, derivatization followed by reductive cleavage, and analytical thioacidolysis. All results demonstrated that the guaiacyl (G) units were predominant in the willow bark lignin over syringyl (S) and minor p-hydroxyphenyl (H) units. Moreover, the monomer yields and S/G ratio rose progressively from bark to inner bark and wood, indicating that lignin may be more condensed in bark than in other tissues. Additionally, major interunit linkage substructures (β-aryl ethers, phenylcoumarans, and resinols) together with cinnamyl alcohol end groups were relatively quantitated by two-dimensional NMR spectroscopy. Bark and inner bark were rich in pectins and proteins, which were present in large quantities and also in the enzyme lignin preparations.
了解柳树皮中木质素的化学结构是设计如何分离其纤维束的不可或缺的步骤。通过核磁共振（NMR）光谱和三种经典的降解方法，即碱性硝基苯氧化、衍生化后还原裂解和分析性硫酸解，对球磨树皮、内皮和木材中依次分离出的全细胞壁和酶木质素进行了比较研究。所有结果表明，柳树皮木质素中的愈创木基（G）单元比丁香基（S）和少量对羟苯基（H）单元更为常见。此外，单体产率和 S/G 比值从树皮到内皮和木材逐渐升高，表明木质素在树皮中的缩合程度可能比在其他组织中更高。此外，通过二维 NMR 光谱相对定量了主要的单元间连接亚结构（β-芳基醚、苯并呋喃和树脂醇）以及肉桂醇端基。树皮和内皮富含果胶和蛋白质，这些物质在酶木质素制剂中大量存在。
