为研究烤烟上部烟叶多糖的结构和保润性能,用碱提法提取大田烤烟上部鲜烟叶多糖并精制后,分别采用HPLC法测定其单糖组分、FTIR法对其官能团进一步表征、SEC/MALLS/RI法测定多糖的分子量及构象,并研究了多糖的热裂解产物和保润性能.结果表明:①烟叶多糖为由42.91%葡萄糖醛酸、8.89%葡萄糖、32.31%甘露糖和15.89%阿拉伯糖组成的酸性杂多糖;为酸性β-吡喃糖.②烟叶多糖的重均分子量为6.587×104;多分散系数MW/Mn为1.557,均方根旋转半径与重均分子量双对数模型中的α值为0.279,表明多糖分子量分布较为均一,在水溶液中为球形并高度分支的构象.③烟叶多糖在600℃和900℃下的裂解产物分别有17和21种.④烟叶多糖具有一定的保润性,其效果低于丙二醇.%In order to investigate the structure and moisture retentivity of polysaccharides in fresh upper leaf of flue-cured tobacco, the polysaccharides in fresh upper leaves sampled from tobacco fields were extracted by alkali extraction method and purified. The monosaccharide composition was determined by HPLC, and functional group was characterized by FTIR. The molecular weight and conformation of the polysaccharides were determined by SEC/MALLS/RI, and the pyrolysis products and moisture retentivity were studied. The results showed that: 1) The polysaccharides were composed of 42.91% glucuronic acid, 8.89% glucose, 32.31%mannose and 15.89% arabinose, and they were acidic β-pyranose. 2) The average molecular weight of tobacco polysaccharides was 6.587 × 104, and the polydispersity coefficient MW/Mn was 1.557, and the α value for the double logarithm model of root mean square (RMS) radius of gyration was 0.279, which indicated that the molecular weight distribution of the polysaccharides was relatively homogeneous with spherical and highly branched conformation in aqueous solution. 3) The numbers of pyrolysis products of polysaccharides were identified to be 17 and 21 at 600 ℃ and 900 ℃, respectively. 4) The polysaccharides in tobacco leaf had a certain moisture retentivity, however their retention effect was lower than that of propylene glycol.
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