目的 从海藻中制备并分离纯化一种低相对分子质量海藻多糖（LMSP），初步分析其结构特征并研究其抗氧化、降血糖和抗肿瘤作用。方法 水提醇沉法制备海藻粗多糖，H₂O₂/维生素C（V_C）法降解海藻多糖，经DEAE-52阴离子交换色谱柱和葡聚糖凝胶G-100色谱柱分离纯化；采用苯酚-硫酸法测定总糖含量，间羟联苯法测定糖醛酸含量，BaCl₂-明胶比浊法测定硫酸基含量，考马斯亮蓝法测定蛋白质含量，高效凝胶渗透色谱测定相对分子质量，进行红外光谱法分析，高效液相色谱测定单糖组成，气相色谱-质谱联用仪检测糖苷键类型，扫描电镜分析形貌特征；1，1-二苯基-2-三硝基苯肼（DPPH）自由基清除率实验、羟自由基清除率实验、2，2-联氮-二（3-乙基-苯并噻唑-6-磺酸）二铵盐（ABTS）自由基清除率实验检测LMSP抗氧化活性；α-淀粉酶抑制实验、α-葡萄糖苷酶抑制实验检测LMSP降血糖活性；检测LMSP对A549、HeLa、Hep-G2细胞的抗肿瘤活性。结果 LMSP的重均相对分子质量为4 635，总糖质量分数为（83.85±2.12）%，糖醛酸的质量分数为（29.73±3.57）%，硫酸根质量分数为（24.44±1.97）%，蛋白质的质量分数为（1.35±0.63）%，主要由半乳糖、木糖和岩藻糖组成，红外光谱及气相色谱-质谱联用对其结构分析推测，该多糖可能是一种含吡喃糖苷的硫酸多糖，主要含有2-Rhap、T-Galp、3-Galp和4-Glcp等片段，LMSP在扫描电镜下呈现出带孔的网状结构，堆叠紧密。LMSP对DPPH自由基清除率、羟基自由基清除率和ABTS自由基清除率的半数抑制浓度（IC₅₀）为1.35、0.61、1.31 mg·mL^-1；对α-淀粉酶和α-葡萄糖苷酶的IC₅₀分别为0.82、1.27 mg·mL^-1；对A549、HeLa和Hep-G2细胞的IC₅₀为2.31、3.41、3.10 mg·mL^-1，且各指标的作用均强于海藻粗多糖。结论 H₂O₂/V_C法降解制备得到均一的LMSP，具有良好的抗氧化、降血糖和抗肿瘤作用。

Objective To isolate and purify a low molecular weight Sargassum polysaccharides (LMSP) from Sargassum of traditional Chinese medicine, and preliminarily analyze its structural characteristics and study its antioxidant, hypoglycemic and antitumor effects. Methods The seaweed polysaccharides were extracted by water extraction and ethanol precipitation, and then degraded by H₂O₂/V_C method. They were purified by DEAE-52 anion exchange column and Sephadex G-100 gel filtration column. The total sugar content was determined by phenol-sulfuric acid method, the sugarfarn acid content was determined by p-hydroxybenzaldehyde method, the sulfate content was determined by BaCl₂-gelatin turbidimetry method, and the protein content was determined by Coomassie brilliant blue method. The relative molecular mass was determined by high-performance gel permeation chromatography, the infrared spectrum was analyzed, and the composition of monosaccharides was determined by highperformance liquid chromatography. The type of glycosidic bond was detected by gas chromatography-mass spectrometry. The morphological features were analyzed by scanning electron microscopy. The antioxidant activity of LMSP was determined by 1,1- diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging rate experiment, hydroxyl radical scavenging rate experiment, and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging rate experiment. The hypoglycemic activity of LMSP was determined by α -amylase inhibition experiment and α -glucosidase inhibition experiment. The antitumor activity of LMSP against A549, Hela, and Hep-G2 cells was determined. Results The relative molecular mass of LMSP is 4 635, with a total sugar content of (83.85±2.12)% and a sugar aldonic acid content of (29.73±3.57)%. The sulfate content is (24.44±1.97)%, the protein content is (1.35±0.63)%, and it is mainly composed of galactose, xylose, and fucose. Infrared spectroscopy and gas chromatography-mass spectrometry were used to analyze its structure, and it was inferred that LMSP may be a pyransulfonic polysaccharide containing pyransulfonic glycosides, mainly containing 2-Rhap, T-Galp, 3-Galp, and 4-Glcp fragments. Under scanning electron microscope, LMSP presents a porous network structure, tightly stacked. The half maximal inhibitory concentration (IC₅₀) for DPPH radical scavenging, hydroxyl radical scavenging, and ABTS radical scavenging were 1.35, 0.61, and 1.31 mg·mL^-1, respectively. The IC₅₀ values for α-amylase and α-glucosidase inhibition were 0.82 and 1.27 mg·mL^-1, respectively. The IC₅₀ values for A549, HeLa, and Hep-G2 cell inhibition were 2.31, 3.41, and 3.10 mg·mL^-1, respectively, and the effects of all indicators were stronger than those of seaweed crude polysaccharides. Conclusion The LMSP prepared by the H₂O₂/V_C method is homogeneous and has good antioxidant, glucose-lowering, and anti-tumor effects.

R284.2

国家科技部重点研发项目（2016YFC0800908）;国家科技部重大研究专项（2014ZX09509）;山东省重点研发项目（2017CXGC1305）