低分子量褐藻多糖的制备及其活性分析

利用抗坏血酸协同过氧化氢法降解褐藻多糖，以DPPH自由基清除率为指标，通过工艺优化得到最佳降解条件，然后用超滤技术将降解产物进行分级，获得不同分子量组分，并分析其DPPH自由基清除率、保湿效果，酪氨酸酶抑制率等活性。正交试验结果表明，最佳降解条件为H₂O₂-V_C浓度20 mmol/L、降解温度45 ℃、降解时间3 h，在此条件下获得的降解产物的DPPH自由基清除率达到61.23%，降解产物得率为73.16%。电泳结果表明，降解后的褐藻多糖的条带明显出现在低分子量区。利用超滤系统将降解产物分级为<5 kDa、5~10 kDa、10~30 kDa、>30 kDa四个不同分子量段的组分，研究发现各分子量段之间的活性存在显著差异（P<0.05），尤其<5 kDa组分（其主要成分为2.140×103 Da，占比29.6%）的活性最好，其DPPH自由基清除率为59.27%，60 h后保湿率为75.75%，酪氨酸酶抑制率为65.28%。与褐藻多糖相比，其糖醛酸含量稍有下降。本研究结果可为褐藻多糖在功能性食品等领域的应用提供理论依据。

Preparation and Biological Activities of Low Molecular Weight Brown Algae

The polysaccharide was degraded by ascorbic acid and hydrogen peroxide, and the optimal degradation conditions were obtained by the index of DPPH free radical scavenging rate. Then the degradation products were classified by ultrafiltration to obtain different molecular weight components, and their activities were analyzed. The optimal degradation conditions were H₂O₂-V_C 20 mmol/L, 45 ℃ and 3 h. Under these conditions, the DPPH free radical scavenging rate reached 61.23%, and the yield of degradation products was 73.16%. Electrophoretic results showed that the bands of the degraded polysaccharides were obviously in the low molecular weight region. Then the degradation products were classified into four different molecular weight fractions, as <5 kDa, 5~10 kDa, 10~30 kDa and >30 kDa by ultrafiltration. There were significant differences among the molecular weight segments (P<0.05), especially the <5 kDa component (main component 2.140×103 Da, 29.6%) had the best biological activity. The DPPH free radical scavenging rate was 59.27%, and the moisture retention rate was 75.75% after 60 h, the tyrosinase inhibition rate was 65.28%. The content of uronic acid of the <5 kDa component decreased slightly compared with polysaccharides. The results could provide theoretical basis for the application of polysaccharides in functional food and other fields.