目的 从黄芪多糖（Astragalus polysaccharides，APS）中分离制备APS-II，探究其体外消化后产物的结构和免疫活性的变化。方法 采用体外模拟唾液、胃液和肠模型研究APS-II经唾液、胃液和小肠液消化后的相对分子质量分布、单糖组成、还原糖含量、官能团和表面形态的变化，同时进行体外免疫活性实验，比较APS-II经体外消化以后的形式及活性的变化。结果 唾液对APS-II无明显影响；而在胃消化0～6 h的过程中，多糖的相对分子质量从5.956×10³降至3.745×10³，还原糖含量从0.333 mg/mL增加至0.348 mg/mL，红外光谱显示在1 649～1 029 cm^-1吸收峰强度不同，游离单糖半乳糖醛酸（galacturonic acid，GalA）被释放；甲基化结果显示发现APS-II经唾液、胃液消化后，糖苷键以1,4葡萄糖连接为主；肠液消化产物中糖苷键存在1,3半乳糖连接。体外免疫活性实验表明，肠液消化产物促进RAW264.7巨噬细胞吞噬活力以及释放一氧化氮（nitric oxide，NO）、白细胞介素-10（interleukin-10，IL-10）、肿瘤坏死因子-α（tumor necrosis factor-α，TNF-α）的能力较强。结论 APS-II在胃肠道中可以被消化，且经胃肠液消化后免疫活性增强，推测与其相对分子质量、单糖组成和糖苷键连接方式相关。

Objective Astragalus polysaccharides (APS)-II was isolated and prepared from APS, and to investigate the changes in structure and immune activity of its products after in vitro digestion. Methods The changes of molecular weight distribution, monosaccharide composition, reducing sugar content, functional groups and surface morphology of APS-II after digestion in saliva, gastric juice and small intestinal juice were studied by in vitro simulated saliva, gastric juice and intestinal model. At the same time, the in vitro immune activity experiment was carried out to compare the changes of form and activity of APS-II after in vitro digestion. Results Saliva had no significant effect on APS-II. In the process of gastric digestion for 0—6 h, the molecular weight of polysaccharide decreased from 5.956×10³ to 3.745×10³, the content of reducing sugar increased from 0.333 mg/mL to 0.348 mg/mL, and the infrared spectrum showed that in the range of 1 649—1 029 cm⁻¹, the absorption peak intensity was different, and the free monosaccharide galacturonic acid (GalA) was released. In addition, the methylation results showed that the glycosidic bonds were mainly 1,4-glucose linkages after digestion with saliva and gastric juice; The glycosidic bonds in the digestive products of intestinal fluid were connected by 1,3 galactose. In vitro immune activity experiments showed that the intestinal digestion product had a strong ability to promote the phagocytic activity of RAW264.7 cells and the release of nitric oxide (NO), interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α). Conclusion APS-II can be digested in the gastrointestinal tract, and the immune activity is enhanced after digestion in the gastrointestinal fluid, which is speculated to be related to its molecular weight, monosaccharide composition and glycosidic bond connection.

R285.5

国家自然科学基金资助项目（81872962）;国家博士后科学基金资助项目（2019M650851）;国家重点研发计划项目（2019YFC1710800）;山西省重点研发计划重点项目（201603D311101）;山西省优秀人才科技创新项目（201605D211030，201705D211020）;山西省科技创新人才团队专项基金