目的:研究和分析板蓝根多糖的化学结构和生物活性。方法:板蓝根水提醇沉后经柱色谱分离纯化,得多糖;采用高效凝胶色谱法(HPGPC)测定各均一多糖的纯度和平均相对分子质量,经UV,IR,NMR,高碘酸氧化和Smith降解法研究各多糖的化学结构,MTT法检测各多糖对巨噬细胞的刺激增殖作用。结果:分离纯化得到板蓝根多糖A,B,C,D,E,各多糖的平均相对分子质量分别为>2 000 kDa,1 757.1,1 342.7,955.6,11.7 kDa。板蓝根多糖A主要由阿拉伯糖组成,多糖E的单糖组成主要为阿拉伯糖和半乳糖,多糖B,C,D均由葡萄糖组成。多糖A,B,C,D,E主要为α糖苷键。多糖A～E中存在1→2,1→3,1→4,1→6多种糖苷键的连接方式。板蓝根多糖C,D,E,对巨噬细胞的刺激增殖指数(SI)分别为5.31,4.76,5.17表现出较强的免疫促进作用。结论:板蓝根多糖A～E为首次从该植物中分离得到的分支多糖。 Objective: To study and analyze the chemical structure and biological activity of Radix Isatidis. Methods: The crude extracts of Radix isatidis were separated and purified by column chromatography to obtain polysaccharides. The purity and average molecular weight of each homogeneous polysaccharide were determined by high performance gel permeation chromatography (HPGPC). UV, IR, Smith degradation method to study the chemical structure of polysaccharides, MTT assay of polysaccharides on macrophages stimulated proliferation. Results: The average molecular weights of polysaccharides A, B, C, D and E were obtained by isolation and purification. The average relative molecular weights of polysaccharides were> 2 000 kDa, 1 757.1, 1 342.7, 955.6 and 11.7 kDa, respectively. Radix isatidis A is mainly composed of arabinose. The monosaccharide composition of polysaccharide E is mainly arabinose and galactose. The polysaccharides B, C and D are composed of glucose. Polysaccharides A, B, C, D, E are mainly α glycosidic bonds. Polysaccharide A ~ E there are 1 → 2,1 → 3,1 → 4,1 → 6 multiple glycosidic bond connection. Radix Isatidis C, D, E, stimulate the proliferation index (SI) of macrophages were 5.31,4.76,5.17 showed a strong immune promoting effect. Conclusion: Radix isatidis A ~ E is a branched polysaccharide isolated from this plant for the first time.