中文摘要：

采用DEAE-琼脂糖凝胶CL-6B凝胶层析对鼠尾藻多糖STP-I进行分离纯化。通过红外光谱法，高碘酸氧化-Smith降解法，甲基化分析以及核磁共振法对多糖STP-I的结构进行分析。建立了STP-I的重复结构单位，STP-I主要由6-β-D-Glcp和4-α-D-Galp组成，还包括5-α-L-Araf、2,3-α-D-Xylp、T-β-D-Xylp和T-β-D-Glcp糖残基。STP-I的分支度是26.7%。基于自由基清除实验，STP-I展现出高于维生素C的抗氧化活性，其清除羟自由基和超氧自由基的EC50值分别是 0.15 mg/mL和1 mg/mL。STP-I对人结肠癌细胞Caco-2具有抑制增值的作用，其IC50是2.56 mg/mL，同时STP-I对正常细胞没有杀伤作用。

英文摘要：

DEAE-Sepharose CL-6B column chromatography was used to separate and purify a polysaccharide STP-I from the algae Sargassum thunbergii.The structural assignment of STP-I was performed using Fourier transform infrared spectroscopy （FTIR） analysis,periodate oxidation-smith degradation,methylation analysis and nuclear magnetic resonance （NMR）.The repeating unit of STP-I was therefore determined.Major sugar residues of STP-I were6-β-D-Glcp and4-α-D-Galp, other residues including 5-α-L-Araf, 2,3-α-D-Xylp, T-β-D-Xylp and T-β-D-Glcp.The degree of branching （DB） of STP-I was 26.7%.On the basis of radical assays,STP-I exhibited higher scavenging activities of hydroxyl and superoxide radicals than Vitamin C with EC50 values of 0.15 and 1 mg/mL,respectively.STP-I also exhibited the capability of anti-proliferation in human colon cancer cells Caco-2 with IC50 value of 2.56 mg/mL,and cause little loss to common cells.