乌龙茶多糖OTPS 2-1的光谱特性、形貌特征及热特性研究

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OTPS2-1.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8.877×10⁴,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7.58:2.14:7.05:1.76:1.02.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pH值显著影响其聚集行为.pH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,有利于提高生物活性.

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

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 8.877×104, 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.