On the base of single factor including extraction temperature, extraction time and the ratio of raw materials to water, experiments, the research aims to explore the suitable consideration considering the optimal conditions of extracting porphyra polysaccharide. According to the experiments, the optimal conditions for extracting porphyra polysaccharide can be as follows:extraction temperature 80℃, extraction time 2 h, the ratio of raw materials to water was 1∶20. Following this, the yield of porphyra polysaccharide could be 3%. On the next stage, Sevag has been employed to remove the obtained protein. After six times, the content of protein can be reduced from 14.31%to 6.0%whilst the content of porphyra polysaccharide can reach 87.66%. The result of antioxidant activity revealed that the extract showed good scavenging effect for ·OH and DPPH·. Besides, there were obvious positive relationship between the concentration and activity of the extract. When the concentration of porphyra polysaccharide was 3 mg/mL,·OH scavenging rate can reach 90.9%;and when the concentration of porphyra polysaccharide was 2.5 mg/mL, DPPH·scavenging rate can reach 90%.%在单因素实验的基础上，对影响紫菜多糖提取得率的因素：提取温度、提取时间、提取料液比设计正交实验。正交实验结果显示：提取温度为80℃、料液比为1∶20、提取时间为2 h，水提醇沉紫菜多糖得率最高。实验中利用Sevag法进行脱蛋白，脱除6次后，蛋白含量从最开始的14.31%降低至6.0%，多糖含量则可以达到87.66%。体外抗氧化活性实验结果表明紫菜多糖具有较强的抗氧化活性，对·OH和DPPH·均有良好的清除效果，并呈现出明显的线性关系。其中当浓度为3 mg/mL时，·OH的清除率可以达到90.9%；当浓度为2.5 mg/mL时，对DPPH·清除率可以达到90%。
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