【摘要】 目的 为探究铁皮石斛多糖的免疫调节活性与其相对分子质量之间的关系，通过超声波联合过氧化氢对铁皮石斛多糖进行降解，获得4个不同相对分子质量的铁皮石斛多糖（Dendrobium officinale polysaccharide, DOP）DOP、DOP-30、DOP-60和DOP-150。方法 采用高效液相色谱、红外光谱、核磁共振波谱等方法对各铁皮石斛多糖样品的结构进行表征，采用小鼠巨噬细胞RAW264.7构建体外免疫活性实验模型，测定细胞的增殖率、吞噬率、一氧化氮（NO）释放量及细胞因子[肿瘤坏死因子-α（tumor necrosis factor-α）], TNF-α)分泌量，探究铁皮石斛多糖相对分子质量对其免疫调节活性的影响。结果 DOP降解后相对分子质量明显降低，降解产物的单糖组成、官能团及糖链主要结构均未发生明显变化，且仍具有三螺旋构象。在12.5～100μg·mL^-1范围内，DOP、DOP-30、DOP-60和DOP-150均可提高RAW264.7细胞的NO释放量和TNF-α分泌量，具有良好的免疫调节活性。结论 铁皮石斛多糖的免疫调节活性受相对分子质量影响较大，相对分子质量最小的DOP-150的免疫增强能力最低，表明在发挥免疫调节活性时需要一定的链长。更多还原

【Abstract】 OBJECTIVE In order to explore the relationship between the immunomodulatory activity of Dendrobium officinale polysaccharide（DOP）and its molecular weight. METHODS DOP was degraded by ultrasonic combined with hydrogen peroxide, and four dendrobium officinale polysaccharides with different molecular weight were obtained, including DOP, DOP-30, DOP-60, and DOP-150. The structures of DOP samples were characterized by high performance liquid chromatography, infrared spectroscopy and nuclear magnetic resonance spectroscopy. Mouse macrophage line RAW 264.7 cells were used to construct an experimental model of immune activity in vitro. The proliferation rate, phagocytosis rate, NO release and tumor necrosis factor-α（TNF-α）secretion of the cells were determined to investigate the effect of DOP′s molecular weight on its immunomodulatory activity. RESULTS The molecular weight of DOP decreased significantly after degradation, and the composition of monosaccharide, functional group and main structures of sugar chain of DOP degradation products did not change significantly, and still had the triple helical conformation. In the range of 12.5-100 μg·mL^-1, DOP, DOP-30, DOP-60 and DOP-150 could increase the proliferation, phagocytosis, NO release and TNF-α secretion of RAW 264.7 cells and showed good immunomodulatory activity. CONCLUSION The immunomodulatory activity of polysaccharides from Dendrobium officinale is significantly affected by the molecular weight, and DOP-150 with the smallest molecular weight has the lowest immunomodulatory activity, which indicating that dendrobium officinale polysaccharides require a certain chain length to exert their immunomodulatory activity.更多还原