Faleva Anna V, Pikovskoi Ilya I, Pokryshkin Sergey A, Chukhchin Dmitry G, Kosyakov Dmitry S
Laboratory of Natural Compounds Chemistry and Bioanalytics, Core Facility Center "Arktika", M.V. Lomonosov Northern (Arctic) Federal University, Northern Dvina Emb. 17, 163002 Arkhangelsk, Russia.
Polymers (Basel). 2022 Feb 28;14(5):964. doi: 10.3390/polym14050964.
Understanding the chemical structure of lignin in the plant phloem contributes to the systematics of lignins of various biological origins, as well as the development of plant biomass valorization. In this study, the structure of the lignin from birch phloem has been characterized using the combination of three analytical techniques, including 2D NMR, Py-GC/MS, and APPI-Orbitrap-HRMS. Due to the specifics of the phloem chemical composition, two lignin preparations were analyzed: a sample obtained as dioxane lignin (DL) by the Pepper's method and DL obtained after preliminary alkaline hydrolysis of the phloem. The obtained results demonstrated that birch phloem lignin possesses a guaiacyl-syringyl (G-S) nature with a unit ratio of (S/G) 0.7-0.9 and a higher degree of condensation compared to xylem lignin. It was indicated that its macromolecules are constructed from β-aryl ethers followed by phenylcoumaran and resinol structures as well as terminal groups in the form of cinnamic aldehyde and dihydroconiferyl alcohol. The presence of fatty acids and flavonoids removed during alkaline treatment was established. Tandem mass spectrometry made it possible to demonstrate that the polyphenolic components are impurities and are not incorporated into the structure of lignin macromolecules. An important component of phloem lignin is lignin-carbohydrate complexes incorporating xylopyranose moieties.
了解植物韧皮部中木质素的化学结构有助于研究各种生物来源木质素的系统分类，以及植物生物质增值利用的发展。在本研究中，结合二维核磁共振（2D NMR）、热解气相色谱/质谱联用（Py-GC/MS）和大气压光电离-轨道阱-高分辨质谱（APPI-Orbitrap-HRMS）这三种分析技术，对桦木韧皮部木质素的结构进行了表征。由于韧皮部化学成分的特殊性，分析了两种木质素制剂：通过佩珀法获得的二氧六环木质素（DL）样品，以及韧皮部经初步碱性水解后得到的DL。所得结果表明，桦木韧皮部木质素具有愈创木基-紫丁香基（G-S）性质，单元比（S/G）为0.7-0.9，与木质部木质素相比具有更高的缩合度。结果表明，其大分子由β-芳基醚构成，随后是苯基香豆素和树脂醇结构以及肉桂醛和二氢松柏醇形式的端基。确定了在碱性处理过程中去除的脂肪酸和黄酮类化合物的存在。串联质谱分析表明，多酚成分是杂质，未并入木质素大分子结构中。韧皮部木质素的一个重要成分是含有木糖吡喃糖部分的木质素-碳水化合物复合物。
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