桑叶多糖SJB的结构分析和蛋白酪氨酸磷酸酯酶PTP1B抑制活性

通过DEAE-纤维素和凝胶过滤柱色谱对桑叶碱提粗多糖进行分级分离, 获得均一多糖SJB, 进行结构鉴定. 采用蛋白酪氨酸磷酸酯酶PTP1B体外模型对SJB进行降血糖活性测定. 结果表明: SJB的相对分子质量为5.4×104, 由鼠李糖、阿拉伯糖、葡萄糖、半乳糖、半乳糖醛酸组成的酸性杂多糖; 主链由1,2-、1,2,4-连接的鼠李糖和1,4-、1,3,4-连接的半乳糖醛酸组成; 侧链包括末端、1,5-、1,3,5-连接的阿拉伯糖; 末端、1,4-连接的葡萄糖以及末端、1,3-、1,4-、1,6-连接的半乳糖, 主要通过鼠李糖的O4位和半乳糖醛酸的O3位与主链相连. 该多糖为首次从桑叶中获得的酸性杂多糖. 20 μg/mL SJB对PTP1B的抑制率为31.7%.

Structural Analysis of Polysaccharide SJB from Mulberry Leaves and Its Inhibitory Activities of Protein Tyrosine Phosphatase-1B

A pectic polysaccharide SJB was obtained from the alkali extract of mulberry leaves by DEAE-cellulose and gel filtration chromatography. The structures of SJB were identified on the basis of chemical methods(sugar component analysis, methylation analysis, partial acid hydrolysis) and spectral method(IR, ESI-MS, NMR). The results show that SJB with a molecular mass of 5.4×104 consisted of rhammose, arabinose, glucose, galactose and galacturonic acid units in the molar ratio of 1.00∶1.26∶0.66∶2.04∶0.95. The main chain of SJB includes 1,2-linked, 1,2,4-linked Rhap and 1,4-linked, 1,3,4-linked GalAp. The side chains are mainly attached to the O4 of Rhap residues and O3 of GalAp residues, including terminal, 1,5-linked, 1,3,5-linked Araf and terminal, 1,4-linked Glcp, and terminal, 1,4-, 1,3-, 1,6-linked Galp. SJB is a new acidic polysaccharide for the first time isolated from Muberry leaves. The study of the effect of lowering blood glucose of SJB shows the inhibitory rate of SJB to PTP1B is 31.7% at the concentration of 20 μg/mL.