新月菱形藻胞外多糖的成分及其硫酸酯的制备

Components of exopolysaccharides of Nitzschia closteriumand preparation of their sulfated products

目的阐明新月菱形藻胞外多糖(exopolysaccharides of Nitzschia closterium,EPN)的成分、单糖组成及其硫酸酯化条件。方法新月菱形藻胞外多糖以醇沉法从该藻的培养液中制备;DEAE-Sephedex25柱分离,HPLC法测定其质量分数,HPLC测定其相对分子质量;以氯磺酸-吡啶法探索新月菱形藻硫酸酯化反应条件。结果新月菱形藻向胞外分泌3种多糖,相对分子质量分别为EPN11.886×105,EPN21.41×105,EPN31.134×105。3种多糖的单糖组成均为甘露糖、鼠李糖、葡萄糖醛酸、葡萄糖和岩藻糖。甘露糖、鼠李糖、葡萄糖醛酸、葡萄糖和岩藻糖的摩尔比在EPN1为4.3∶1∶5.1∶8.9∶5.6,EPN2为4.2∶7.3∶3.7∶12.8∶3.4,EPN3为3.5∶2.1∶4.3∶4.9∶4.7。3种多糖的硫酸酯化条件基本一致,提高氯磺酸比例和延长反应时间均有利于增加酯化产物的硫酸根、提高取代度和酸酯化反应的产率。结论新月菱形藻胞外多糖为酸性多糖,其硫酸酯化产物多糖硫酸酯可能具有潜在的药理活性。

Objective To elucidate the components of exopolysaccharides of Nitzschia closterium （EPN）, the components of monosaccharide in each EPN, and the conditions for preparing their sulfated products. Methods The EPNs were prepared from the nutrient solution by ethanol precipitation and separated by DEAE-Sephadex 25 column. The purity and the relative molecular weight of each EPN were determined by HPLC. The chlorosulferic acid-pyridine method was used for investigating conditions of EPN sulfation. Results The EPNs were constituted by three polysaccharides with their molecular weight 1. 886 × 10^5（EPN1）, 1.41× 10^5（EPN2）, and 1. 134× 10^5（ENP3）, respectively. The monosaccharides in three EPNs all comprised mannose （Man）, rhamnose （Rha）, glucuronic acid （GluA）, glucose （Glu）, and fucose （Fuc）, whose ratio was 4.3 ： 1 ： 5.1 ： 8.9 ： 5.6 in EPN1, 4.2 ： 7.3 ： 3.7 ： 12.8 ： 3.4 in EPN2, and 3.5 ： 2.1 ： 4.3 ： 4.9 ： 4.7 in EPN3. The conditions for sulfation of EPNs were nearly identical, namely, increasint the ratio of chlorosulferic acid and elongation of reaction time favored in obtaining higher content of sulfate, degree of sulfation in EPN molecular, and percent of sulfated products. Conclusion The EPNs are acidic polysaccharides. Their sulfated products - sulfated polysaccharides may be of potential pharmacological activities.