本文采用水提法、酸提法和酶提法提取龙须菜多糖，比较了不同方法对提取率的影响，并测定了酸提法制备的龙须菜多糖的化学组成及免疫活性。结果发现：采用柠檬酸提取龙须菜多糖的提取率最高，为27.66±0.49%，为水提法的1.86倍；其产物多糖的总糖含量、蛋白质含量、糖醛酸含量以及硫酸基含量分别为62.24±1.09%、1.54±0.15%、6.25±0.72%和16.74±0.11%，未检出多酚类物质。此外，龙须菜多糖对RAW 264.7细胞具有显著的促增殖作用，并且能够显著地提高RAW 264.7细胞吞噬中性红的能力；且龙须菜多糖不仅能够提高光老化小鼠的胸腺指数和脾脏指数，还能降低小鼠血清白介素-10的含量，提高小鼠血清肿瘤坏死因子-α的含量，这些研究表明龙须菜多糖具有较强的提高小鼠免疫功能的能力，能够缓解光老化过程中的免疫抑制现象。

The polysaccharides from Gracilaria lemaneiformis were exacted using hot water, different acids, and enzymes. The effects of different methods on the extraction rate were compared, and the chemical composition and immunoregulatory activity of polysaccharides extracted using acids were evaluated. The results showed that the yield of the polysaccharides extracted using citric acid was the highest (27.66 ± 0.49%), which was 1.86 times those extracted using hot water. The amounts of total sugar, proteins, uronic acids, and sulfates of the polysaccharides exacted using citric acid were 62.24 ± 1.09%, 1.54 ± 0.15%, 6.25 ± 0.72%, and 16.74 ± 0.11%, respectively. No polyphenols were detected. In addition, the polysaccharides extracted using citric acid significantly promoted the proliferation of RAW 264.7 cells, and enhanced their pinocytic capability. G. lemaneiformis polysaccharide improved the thymus and spleen indices in photoaged mice, as well as reduced the concentration of interleukin-10 and increased tumor necrosis factor-α content in mouse serum. These findings suggest that G. lemaneiformis polysaccharides have a relatively high capacity to enhance the immune functions of mice and can alleviate immunosuppression during the photoaging process.

广东省自然科学基金项目（2014A030313242）；中央高校基本科研业务费项目（2015ZZ110）；广东省特支计划青年拔尖人才项目（2015TQ01N670）；广州市珠江科技新星项目（201610010096）