烟草木质素结构的二维核磁共振波谱表征

Structure characterization of tobacco lignin by Two-dimensional Nuclear Magnetic Resonance spectroscopy

【背景和目的】烟草木质素对烟草品质和安全性有重要影响,为了提高烟草制品的质量,需要探究烟草木质素的化学结构及含量。【方法】利用二维异核单量子相干核磁共振技术(2D HSQC NMR)建立表征烟草木质素的方法,实现烟草木质素的结构表征及半定量分析。【结果】(1)烟草样品木质素中共发现10种主要的木质素基本单元及单元间连接键结构,27种相关结构的信号。(2)烟草样品木质素是SGH型木质素,愈创木基(G)是最主要的基本单元,含量在50.72%~73.50%范围内,紫丁香基(S)的含量在15.62%~26.51%范围内,对羟基苯基(H)的含量在5.66%~28.90%范围内;β-芳基醚单元β-O-4(A)是最主要的单元间连接键,含量在72.93%~92.97%范围内,树脂醇单元β-β(C)次之,含量在3.88%~15.81%范围内。(3)烤烟烟叶部位自上而下,紫丁香基(S)单元的含量逐渐减少,愈创木基(G)和对羟基苯基(H)单元的含量逐渐增加。梗丝和烟草薄片与烟叶相比,愈创木基(G)单元的含量较高,对羟基苯基(H)单元的含量较低,β-芳基醚单元β-O-4(A)的含量较低,树脂醇单元β-β(C)的含量较高。【结论】本研究实现了不同烟草木质素的基本单元及单元间连接键结构的定性表征和半定量分析,提出烟草木质素分子的结构示意图,为烟草木质素大分子研究提供一定的理论和技术基础。

[Background and Objective] Lignin has an important effect on tobacco quality and safety. In order to improve the quality of tobacco products, it is necessary to study the chemical structure and content of tobacco lignin. [Methods] In this study, tobacco lignin was characterized by two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance(2D HSQC NMR), and the structure characterization and semi-quantitative analysis of tobacco lignin were studied. [Results] Test data show: 1) There were 10 kinds of lignin subunits and linkages and 27 signals of related structures were found in tobacco lignin;2) Tobacco sample lignin is a SGH type lignin.Guaiacyl(G) is the most important lignin subunit, of which the content ranges from 50.72 to 73.50 percent;the content of syringyl(S) is between 15.62 and 26.51 percent, and the content of p-hydroxyphenyl(H) is between 5.66 and 28.90 percent. β-aryl ether units β-O-4(A)are the most important lignin linkages, whose content ranges from 72.93 to 92.97 percent of the whole linkages of lignin, followed by resinol units β-β(C) in the range of 3.88-15.81 percent;3) From the top to the bottom of flue-cured tobacco leaves, the content of syringyl(S) units gradually decreases, while the content of guaiacyl(G) and p-hydroxyphenyl(H) units gradually increases. Compared with tobacco leaves, the content of guaiacyl(G) units is higher in cut stem and tobacco sheet, but the content of p-hydroxyphenyl(H) units is lower.However, the content of β-aryl ether units β-O-4(A) is lower, and the content of resinol units β-β(C) is higher. [Conclusion] In this paper,qualitative and semi-quantitative analysis of lignin subunits and linkages of different tobacco samples were realized by using 2D HSQC NMR method, and the model of tobacco lignin molecular structure was proposed. These results provide a theoretical and technical basis for the study of tobacco lignin macromolecules.