为比较不同修饰方法对海带多糖的结构和自由基清除能力的影响，分别采用羧甲基化、硫酸酯化和磷酸化对海带多糖进行化学修饰，综合运用紫外光谱、傅里叶变换红外光谱、刚果红实验、高碘酸氧化和自由基清除能力实验，比较修饰前后海带多糖结构和DPPH•、•OH、O2-•清除能力差异。结果显示，-OH分别转化为-COO、O-S和P-OH，说明羧甲基化、硫酸酯化和磷酸化修饰海带多糖成功，且与修饰前相比，修饰后三股螺旋结构均消失；修饰前后糖苷键的键型存在显著差异：海带多糖和磷酸化海带多糖糖苷键键型均为(1→6)、(1→2、1→4)、(1→3)，摩尔比分别为0.04:0.05:0.91、0.03:0.05:0.92，而羧甲基化、硫酸酯化海带多糖糖苷键键型为(1→2、1→4)、(1→3)，摩尔比分别为0.02:0.98、0.10:0.90。羧甲基化和磷酸化海带多糖对DPPH•、•OH、O2-•的清除率分别提高了7.38%、12.17%、0.78%和9.12%、40.22%、14.52%，硫酸酯化海带多糖对DPPH.、O2-•的清除率分别提高了24.48%、5.16%，但削弱了对•OH的清除能力，清除率降低34.82%；综合评价分析羧甲基化、硫酸酯化和磷酸化海带多糖的自由基半数抑制浓度IC50分别为2.53、4.03、1.66 mg/mL，说明磷酸化修饰在改善海带多糖的自由基清除能力方面优于羧甲基化与硫酸酯化修饰。

To compare the effects of different modification methods on the structures and free radical scavenging abilities of Laminaria japonica polysaccharides, carboxymethylation, sulfation and phosphorylation methods were used to modify chemically Laminaria japonica polysaccharides. Ultraviolet spectroscopy, Fourier transform infrared spectroscopy, Congo red experiment, periodate oxidation and free radical scavenging ability experiments were used to compare the differences in the structure and DPPH•, •OH and O2-• scavenging abilities of Laminaria japonica polysaccharides before and after modification. The results showed that -OH was transformed into -COO, O-S and P-OH, respectively, indicating that carboxymethylation, sulfation and phosphorylation of Laminaria japonica polysaccharides were successful in the modification of Laminaria japonica polysaccharides. Compared with the polysaccharide before modification, the threestrand helix structure disappeared after modification. There were significant differences in the bond types of glycosidic bonds before and after modification: the glycosidic bond types of the Laminaria japonica polysaccharides and the phosphorylated Laminaria japonica polysaccharides were (1→6), (1→2, 1→4), (1→3), with their molar ratios being 0.04:0.05:0.91 and 0.03:0.05:0.92, respectively. The glycosidic bond types of carboxymethylated Laminaria japonica polysaccharide and sulfated Laminaria japonica polysaccharide were (1→2, 1→4) and (1→3), with their molar ratios being 0.02:0.98 and 0.10:0.90, respectively. The scavenging rates of carboxymethylated Laminaria japonica polysaccharide and phosphorylated Laminaria japonica polysaccharide against DPPH•, •OH and O2-• increased by 7.38%, 12.17% and 0.78%, and 9.12%, 40.22% and 14.52%, respectively. The scavenging rates of sulfated Laminaria japonica polysaccharides against DPPH• and O2-• increased by 24.48% and 5.16%, respectively, whilst the scavenging ability against •OH was weakened, with the scavenging rate being reduced by 34.82%. The analysis of comprehensive scores revealed that the half-maximal inhibitory concentrations (IC50 values) of the carboxymethylated, sulfated and phosphorylated Laminaria japonica polysaccharides were 2.53, 4.03 and 1.66 mg/mL, respectively, indicating that phosphorylation modification was superior to carboxymethylation modification and sulfation modification in improving the free radical scavenging ability of Laminaria japonica polysaccharide.

广西科技计划项目（桂科AD201590632023；GXNSFBA026053）；国家自然科学基金项目（32001208；32460318）；广西产研计划项目（CYY-HT2023-JSJJ-0038）；国家级大学生创新创业训练计划项目（202310594022）