目的 从黄芪多糖（Astragalus polysaccharides，APS）中分离制备出2种多糖APS-Ⅰ（相对分子质量＞2 × 10⁶）、APS-Ⅱ（相对分子质量1 × 10⁴），明确APS、APS-Ⅰ、APS-Ⅱ对葡聚糖硫酸钠（dextran sulphate sodium，DSS）诱导的小鼠溃疡性结肠炎的疗效。方法 对APS-Ⅰ、APS-Ⅱ进行分离制备，并进行相对分子质量、糖醛酸含量、单糖组成以及糖苷键连接方式测定。建立BALB/c小鼠溃疡性结肠炎模型，分别给予APS、APS-Ⅰ、APS-Ⅱ，记录小鼠疾病活动指数（disease activityindex，DAI）评分、结肠长度、脾脏指数、肝脏指数；采用苏木素-伊红（HE）染色观察结肠组织病理变化；测定结肠组织髓过氧化物酶（myeloperoxidase，MPO）活性和Th1相关细胞因子肿瘤坏死因子-α（tumor necrosis factor-α，TNF-α）、γ干扰素（interferon-γ，IFN-γ）以及Th2相关细胞因子白细胞介素-4（interleukin-4，IL-4）、IL-10水平；采用qRT-PCR检测结肠组织TNF-α、IFN-γ、IL-4、IL-10 mRNA表达；免疫组化法测定结肠组织T细胞特异性转录因子（transcription factor T-bet，T-bet）、GATA结合蛋白3（GATA binding protein 3，GATA-3）蛋白表达，比较APS、APS-Ⅰ、APS-Ⅱ疗效。结果 APS中共有2个组分APS-Ⅰ、APS-Ⅱ，其相对分子质量分别为＞2 × 10⁶、1 × 10⁴，糖醛酸质量分数分别为26.25%、1.62%。单糖结果显示，APS-Ⅰ和APS-Ⅱ均由甘露糖、鼠李糖、半乳糖醛酸、葡萄糖、半乳糖、阿拉伯糖组成，APS-Ⅰ中甘露糖、阿拉伯糖和半乳糖占比均大于APS-Ⅱ。糖苷键结果显示，APS-Ⅰ以1,4连接的葡萄糖和1,6连接的半乳糖为主，APS-Ⅱ以1,4连接的葡萄糖为主。与模型组比较，APS-Ⅰ可显著改善结肠长度降低、体质量减轻、DAI评分增加、脾脏和肝脏指数增加等临床症状（P＜0.05、0.01、0.001），减轻结肠组织病理损伤，降低结肠组织中MPO活性及TNF-α、IFN-γ水平（P＜0.01、0.001），升高结肠组织中IL-4、IL-10水平（P＜0.05、0.01、0.001），下调结肠组织TNF-α、IFN-γ mRNA表达和T-bet蛋白表达（P＜0.05、0.001），上调IL-4、IL-10 mRNA表达和GATA-3蛋白表达（P＜0.05、0.01）。而APS-Ⅱ在MPO活性、IFN-γ水平以及IL-4、IL-10 mRNA表达和T-bet、GATA-3蛋白表达方面与模型组相比无显著差异。结果表明APS-Ⅰ对溃疡性结肠炎的治疗效果优于APS-Ⅱ。结论 APS-Ⅰ是APS治疗溃疡性结肠炎的主要成分，其活性可能与其糖醛酸含量、多糖的种类以及糖苷键连接方式有关，APS-Ⅰ治疗溃疡性结肠炎可能通过调节Th1/Th2免疫平衡实现。

Objective To isolate Astragalus polysaccharides-I (APS-I) (relative molecular mass > 2×10⁶) and APS-II (relative molecular mass 1×10⁴) from APS, and further clarify the efficacy of APS, APS-I and APS-II on dextran sulphate sodium (DSS)- induced ulcerative colitis in mice. Methods APS-Ⅰ and APS-Ⅱ were isolated and prepared, relative molecular mass, uronic acid content, monosaccharide composition and glycosidic linkage were determined. The BALB/c mice model of ulcerative colitis was established, APS, APS-I and APS-II were given. The disease activity index (DAI), colon length, spleen index and liver index of mice were measured; Hematoxylin-eosin (HE) staining was used to observe pathological changes in colon tissue; The activity of myeloperoxidase (MPO) and levels of Th1 related cytokines tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), as well as Th2 related cytokines interleukin-4 (IL-4) and IL-10 in colon tissue were measured; qRT-PCR was used to detect the mRNA expressions of TNF-α, IFN-γ, IL-4 and IL-10 in colon tissue; Immunohistochemical method was used to measure the expressions of T cell specific transcription factor T-bet (T-bet) and GATA binding protein 3 (GATA-3) protein in colon tissue. The efficacy of APS, APS-I and APSII was compared. Results APS was composed of two components APS-I and APS-II, with relative molecular weights > 2×10⁶ and 1×10⁴, respectively; The mass fractions of uronic acid were 26.25% and 1.62%, respectively. The monosaccharide results showed that APS-I and APS-II were both composed of mannose, rhamnose, galacturonic acid, glucose, galactose and arabinose. The proportion of mannose, arabinose and galactose in APS-I was higher than that in APS-II. The glycosidic bond results showed that APS-I was mainly composed of 1,4-linked glucose and 1,6-linked galactose, while APS-II was mainly composed of 1,4-linked glucose. Compared with model group, APS-I could significantly improve clinical symptoms such as decreased colon length, decreased body weight, increased DAI score, increased spleen and liver indexes (P < 0.05, 0.01, 0.001), alleviate pathological damage to colon tissue, reduce MPO activity and levels of TNF-α, IFN-γ in colon tissue (P < 0.01, 0.001), increase IL-4 and IL-10 levels in colon tissue (P < 0.05, 0.01, 0.001), down-regulate TNF-α, IFN-γ mRNA expressions and T-bet protein expression in colon tissue (P < 0.05, 0.001), upregulate IL-4, IL-10 mRNA expressions and GATA-3 protein expression (P < 0.05, 0.01). However, APS-II showed no significant differences compared to model group in terms of MPO activity, IFN-γ level, expressions of IL-4, IL-10 mRNA and T-bet, GATA-3 protein. The results indicated that APS-Ⅰ had a better therapeutic effect on ulcerative colitis than APS-Ⅱ. Conclusion APS-Ⅰ is the main component of APS in the treatment of ulcerative colitis, and its activity may be related to its uronic acid content, type of polysaccharide and glycosidic bond connection mode. APS-Ⅰ may treat ulcerative colitis by regulating Th1/Th2 immune balance.

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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