落叶松树皮缩合单宁的表征及酸催化解聚,RSC Advances

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落叶松树皮缩合单宁的表征及酸催化解聚
RSC Advances ( IF 3.9 ) Pub Date : 2017-07-12 00:00:00 , DOI: 10.1039/c7ra03410e
Aibin Zhang _{1,

2,

3,

4,

5} , Jiongjiong Li _{1,

2,

3,

4,

5} , Shifeng Zhang _{1,

2,

3,

4,

5} , Youbing Mu _{6,

7,

8,

9,

10} , Wei Zhang _{1,

2,

3,

4,

5} , Jianzhang Li _{1,

2,

3,

4,

5}

Affiliation

落叶松树皮提取物中的浓缩单宁是一种天然的可再生且环保的材料，并且是酚醛石化产品的潜在替代品。但是，单宁的广泛应用受到其低反应性的限制。因此，本研究的目的是通过解聚提高落叶松单宁的反应性，并确定最佳的反应条件。落叶松单宁和解聚落叶松单宁的结构通过傅里叶变换红外光谱（FT-IR）表征，固相¹³C-NMR和基质辅助激光解吸电离飞行时间（MALDI-TOF）质谱。通过热重分析（TGA）评价解聚前后落叶松单宁的热稳定性。结果表明，落叶松单宁的单体单元主要由儿茶素/表儿茶素，金属没食子儿茶素/表没食子儿茶素，儿茶素-没食子儿茶素酯和二苯乙烯苷组成。还观察到存在儿茶素没食子酸酯二聚体，其失去了没食子酸残基和羟基以及少量的非塞替丁单元。此外，从MALDI-TOF MS数据中观察到了一系列峰，这些峰对应于最多11个重复单元的落叶松单宁的寡聚体。解聚处理，特别是使用2-巯基乙醇作为亲核试剂，业已发现有利于提高热稳定性。解聚反应的优化使反应在60°C下以2-巯基乙醇为亲核试剂和0.1 mol L在2小时内完成^-1盐酸。在这些反应条件下获得了许多分子量小于600 Da的化合物，主要是二聚体和单体。

"点击查看英文标题和摘要"

Characterization and acid-catalysed depolymerization of condensed tannins derived from larch bark

Condensed tannins from larch bark extracts are a natural renewable and eco-friendly material and are potential substitutes for phenolic petrochemicals. However, the wide application of tannin is restricted by its low reactivity. Therefore, the goal of this study was to enhance the reactivity of larch tannin by depolymerization and determine optimal reaction conditions. The structures of larch tannin and depolymerized larch tannin were characterized by Fourier transform infrared (FT-IR) spectroscopy, solid phase ¹³C-NMR and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. The thermal stability of larch tannin before and after depolymerization was evaluated by thermogravimetric analysis (TGA). The results indicated that the monomeric units of larch tannin were mainly composed of catechin/epicatechin, gallocatechin/epigallocatechin, catechin–gallocatechin esters, and stilbene glucosides. The presence of a catechin gallate dimer that had lost both gallic acid residues and a hydroxy group and a small amount of fisetinidin units were also observed. Additionally, a series of peaks corresponding to oligomers of larch tannin of up to 11 repeating units were observed from the MALDI-TOF MS data. Depolymerization treatment, especially using 2-mercaptoethanol as a nucleophilic reagent, was found to be beneficial to the enhancement of thermal stability. The optimization of the depolymerization reaction allowed the reaction to be completed in two hours, at 60 °C, using 2-mercaptoethanol as a nucleophile and 0.1 mol L⁻¹ HCl. Many compounds of molecular weight less than 600 Da, mainly dimers and monomers, were obtained under these reaction conditions.

更新日期：2017-07-12

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