Abstract:To investigate the effects of different extraction methods on the polysaccharides of Caulerpa lentillifera and their in vitro antioxidant activities，the polysaccharides were successively extracted by extrusion extraction，water bath extraction and alkali extraction. The extraction rates，monosaccharide compositions and relative molecular masses of the polysaccharides obtained by different extraction methods were compared. The antioxidant activities were investigated by measuring the scavenging abilities of DPPH radicals，free radicals and hydroxyl radicals. The results showed that the extraction rates of polysaccharides obtained by different extraction methods were in the order of alkali extraction＞water bath extraction＞extrusion extraction，which were 28.83%，5.30% and 3.85%，respectively. The monosaccharide compositions of the polysaccharides obtained by extrusion extraction and water bath extraction were similar，mainly consisting of galactose，glucose，xylose and mannose. The monosaccharide composition of the polysaccharides obtained by alkali extraction was xylose，which was identified as β-1，3-xyloglucan. The antioxidant activities of the polysaccharides obtained by different extraction methods also showed certain differences. The polysaccharides obtained by alkali extraction had the strongest scavenging abilities for DPPH radicals and hydroxyl radicals，especially for hydroxyl radicals，reaching up to 97.60%. The polysaccharides obtained by water bath extraction had the strongest scavenging ability for free radicals，followed by alkali extraction and extrusion extraction. It was found that β-1，3-xyloglucan showed the best antioxidant activity and presented a concentration-dependent manner.