海带多糖羧甲基化修饰工艺优化及其生物活性研究

Optimization of carboxymethylation modification process and study on biological activity of Laminaria japonica polysaccharide

为优化海带多糖羧甲基化修饰工艺,并研究修饰前后海带多糖的结构与生物活性,该研究通过单因素试验和正交试验对海带多糖羧甲基化修饰进行工艺优化,采用紫外光谱、傅里叶变换红外光谱、高碘酸氧化、刚果红实验对修饰前后多糖进行结构表征,比较修饰前后海带多糖对自由基的清除能力与降血糖活性差异。结果表明,最佳工艺条件为碱化温度50℃、反应时间4.0 h、反应温度65℃、多糖与氯乙酸质量比为3∶7,最高取代度为0.304;红外光谱指征羧甲基化修饰成功,修饰后三股螺旋结构消失,羧甲基化多糖为吡喃型多糖,糖苷键连接方式主要为(1→3)和(1→2,1→4),摩尔比为0.977∶0.023;羧甲基化修饰显著提高了海带多糖对DPPH自由基、羟自由基和超氧阴离子自由基的清除能力,清除率分别提高了7.38%、12.17%、0.78%(P<0.05),但降血糖活性无显著差异,说明在应用羧甲基化修饰促进海带多糖生物活性时可优先从其对自由基的清除能力的角度考虑。

This study aimed to optimize the carboxymethylation modification process of Laminaria japonica polysaccharide and study the structure and biological activity of Laminaria japonica polysaccharide before and after modification.The process of carboxymethylation modification of Laminaria japonica polysaccharide was optimized by a single-factor test and an orthogonal test.The structure of Laminaria japonica polysaccharide before and after modification was characterized by ultraviolet spectroscopy,Fourier transform infrared spectroscopy,periodate oxidation,and Congo red experiment.The differences in free radical scavenging ability and hypoglycemic activity of Laminaria japonica polysaccharide before and after modification were compared.Results showed that the optimum conditions were that the alkalization temperature was 50℃,the reaction time was 4.0 h,the reaction temperature was 65℃,the mass ratio of polysaccharide to chloroacetic acid was 3∶7,and the highest substitution degree was 0.304.Infrared spectroscopy indicated that the carboxymethylation modification was successful,and the triple helix structure disappeared after modification.The carboxymethylated polysaccharide was a pyranoid polysaccharide,and the glucosidic linkages were mainly(1→3)and(1→2,1→4),and the molar ratio was 0.977∶0.023.Carboxymethylation modification significantly improved the scavenging ability of Laminaria japonica polysaccharides on DPPH free radicals,·OH,and·O-2,and the scavenging rates increased by 7.38%,12.17%,and 0.78%,respectively(P<0.05),but there was no significant difference in hypoglycemic activity.These results indicate that the application of carboxymethylation modification to promote the biological activity of Laminaria japonica polysaccharide can give priority to its free radical scavenging ability.