本文以龙须菜为原料，比较了热水、超声、超声协同热水和柠檬酸提取4种方法所得多糖的性质。研究表明：柠檬酸提取所得多糖的得率最高，为17.81±0.34%，其多糖分子量和粘度较低，多糖分子量的均一性较高。抗氧化实验表明，柠檬酸提龙须菜多糖具有较高的抗氧化性，其氧自由基清除能力（ORAC）值可达298.735±6.57 μmol Trolox/g，在多糖浓度为2.0 mg/mL时，DPPH自由基清除率可达65.79±0.3%，还原力为0.765±0.01，均显著高于其他方法所提多糖。柠檬酸提多糖能够有效地抑制α-淀粉酶的活性。相关性分析表明，龙须菜多糖的多糖含量及糖醛酸含量与抗氧化、α-淀粉酶抑制活性之间呈正相关，而硫酸基含量、分子量、PDI值和粘度与抗氧化、α-淀粉酶抑制活性之间呈负相关。因此，柠檬酸提取是一种有效的提取龙须菜多糖的方法。该法能有效地提高多糖得率，增加产物中糖醛酸含量，降低硫酸基含量、分子量及其粘度，并提高多糖分子量的相对均一性。

Gracilaria lemaneiformis was used as the raw material to compare the properties of four polysaccharide extraction processes: GWP, GUP, GUWP, and GCP, which involve extractions using hot water, ultrasonic waves, ultrasonic-hot water, and citric acid, respectively. The results showed that GCP had the highest yield of 17.81 ± 0.34% among the four polysaccharides, relatively low molecular weight and apparent viscosity, and a high degree of uniformity of molecular weight. Antioxidant activity analyses indicated that GCP exhibited a relatively strong antioxidant capacity, and the oxygen radical absorbance capacity (ORAC) value was 298.735 ± 6.57 μmol Trolox/g. When the concentration of GCP was 2.0 mg/mL, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and the reducing power were 65.79 ± 0.3% and 0.765 ± 0.01, respectively, which were significantly higher than the values of polysaccharides extracted using other methods. In addition, GCP could effectively inhibit α-amylase activity. Correlation analysis showed that the antioxidant activity and inhibitory effect on α-amylase of the polysaccharides from Gracilaria lemaneiformis had a positive correlation with the content of polysaccharides and uronic acid, and a negative correlation with the sulfate group content, molecular weight, polydispersity index (PDI) value, and viscosity. Therefore, citric acid extraction is an effective method to extract polysaccharides from G. lemaneiformis. This method can effectively increase the polysaccharide yield and the uronic acid content in the product, reduce the sulfate group content, molecular weight, and viscosity, and improve the molecular weight uniformity of polysaccharides.

广东省自然科学基金（2014A030313242）；中央高校科研业务费项目（海藻多糖抗皮肤光老化的功效及机理研究）；广东省领军人才项目（Rui Hai Liu）；广东省科技计划项目（2013B090700008）；SRP项目《生物活性多糖的分离纯化及功效研究》