乌龙茶多糖OTPS 2-1的光谱特性、形貌特征及热特性研究

Spectrum, Morphological and Thermal Characteristics of OTPS 2-1 in Polysaccharides from Oolong Tea

采用纤维素和葡聚糖凝胶柱层析法分离纯化 ,获得乌龙茶多糖主要组分 OTPS 2 -1 .经 GC,HPLC,UV,IR和 GPC-LLS证实 OTPS2 -1是富含糖醛酸和少量蛋白质的三元糖复合物 ,相对重均分子量为8.877× 1 0 4 ,糖基由半乳糖、葡萄糖、阿拉伯糖、岩藻糖和鼠李糖组成 ,其摩尔比为 7.5 8∶ 2 .1 4∶ 7.0 5∶1 .76∶ 1 .0 2 .利用 AFM,QELS及 LSCM观察 OTPS2 -1在溶液中的形貌特征 ,结果表明 ,OTSP2 -1在溶液中呈直径 0 .2～ 0 .5μm、高度 0 .3～ 0 .6μm的短棒形不均一聚集体 ,并具有强烈的荧光 ,溶液的 p H值显著影响其聚集行为 .p H值、离子强度和络合物等环境因素的改变 ,均导致多糖立体构象和非对称性的变化 .OTPS2 -1在 SEM低倍镜下呈折叠卷曲形貌 ,在高倍镜下呈现平整的图像 .综合热分析结果表明 ,在加热过程中 ,多糖有 3次大的质量损失过程 ,出现 3次吸热峰和放热峰 .提示茶叶经过半发酵处理后 ,多糖组成、分子质量分布以及分子间相互作用可引起微观形貌、链构象和聚集行为的变化 。

OTPS 2-1, a main constituent of OTPS, was obtained by DEAE-52 and Sephadex G-150 column chromatography. It was found that OTPS 2-1 was a trinal compound of polysaccharide containing rich uronic acid and little protein by using methods of UV, IR, GC, HPLC and GPC-LLS. The results showed that the average molecular weight of OTPS 2-1 was 8.877×10 4, and it was composed of Gal, Glu, Ara, Fuc and Rha with a molar ratio of 7.58∶2.14∶7.05∶1.76∶1.02. By using the technique of AMF, QELS, CD and LSCM, the three-dimensional conformation and solution behavior were studied. The results also showed that the molecule of OTPS 2-1 twisted each other, which formed short stick of 0.2—0.5 μm in diameter and 0.3—0.6 μm in length with a strong fluorescent light. The conformation could be changed by the factors of pH, ion intensity and complex compound. By using SEM, the folding and curling image under low-powered microscope, but smooth figure under high-powered microscope were also observed. Thermal analysis of OTPS 2-1 also indicated that there appeared 3 endothermic peaks and 3 exothermic peaks during heating.