莲藕不同部位多糖的理化特征与抗氧化活性研究

采用分步醇沉法制备莲藕食用部位、皮和节中多糖(EP60/75/90、PP60/75/90和NP60/75/90),分析其基本组成、理化特征及抗氧化活性,明确活性多糖在莲藕中的分布。不同部位多糖的组成存在明显差异,其中由食用部位制备多糖的纯度较低。高效分子排阻色谱分析发现,莲藕不同部位多糖均以1.30~1.63ku的低分子组分为主,且含有少量的结合蛋白。体外抗氧化活性评价发现:食用部位多糖的抗氧化活性较藕皮多糖和藕节多糖弱,尤其是DPPH自由基清除能力和FRAP总抗氧化能力(p<0.05)；藕皮多糖的抗氧化活性均为PP60>PP75>PP90；藕节多糖NP60和NP90的活性相当,其羟自由基清除能力强于NP75(p<0.05),而FRAP总抗氧化能力则较弱(p<0.05)。莲藕抗氧化活性多糖主要分布于皮和节中,其活性强弱可能与结合蛋白含量和分子量的高低有关。

Study on Physicochemical Characteristics and Antioxidant Activities of Polysaccharides from Different Parts of Lotus Root

To explore the distribution of polysaccharides with higher antioxidant activities in lotus root, polysaccharides in edible part, peel, and node (i.e. EP60/75/90, PP60/75/90 and NP60/75/90) were respectively isolated using a precipitation method coupled with gradually increased alcohol concentrations. While the basic components, physicochemical characteristics, and antioxidant activities were further analyzed. Polysaccharides from different parts of lotus root showed obvious differences in composition, and edible part polysaccharides (EPs) had lower purities compared with peel polysaccharides (PPs) and node polysaccharides (NPs). Based on high performance molecular-exclusion chromatography, it was found that lotus root polysaccharides were mainly composed of fractions with low molecular weight (1.30-1.63ku) and less binding protein. The antioxidant evaluations in vitro confirmed that the antioxidant activities of EPs were weaker than those of PPs and NPs, especially DPPH radical scavenging ability and FRAP total antioxidant capacity (p<0.05). The antioxidant activities of PPs could be ordered as PP60>PP75>PP90. Meanwhile, the activities of NP60 and NP90 were matched, which exhibited stronger hydroxyl radical scavenging capacities and weaker FRAP total antioxidant capacities than NP75 (p<0.05). The polysaccharides with higher antioxidant activities mainly exist in the peel and node of lotus root, which might be related to binding protein content and molecular weight.