Structural characterization of water-soluble polysaccharide from Arctium lappa and its effects on colitis mice

•Polysaccharide from Actium lappa was purified into a fraction (ALP-1).•ALP-1 was identified to be an inulin-neoseries fructan.•ALP-1 could inhibit the colitis in mice induced by DSS.•ALP-1 could accommodate inflammatory cytokines in colitis mice.•ALP-1 ameliorated intestinal microbiota in colitis mice. In this study, water-soluble polysaccharide from Arctium lappa was extracted, isolated and purified to be a fraction (ALP-1). Characterization of structure revealed that ALP-1 was a kind of fructan with a molecular weight of 5.12 × 103 Da. ALP-1 was composed of (2→ 1)-β-d-fructofuranose backbone linked to a terminal of (2 → 1)-α-d-glucopyranose at the non-reducing end and a (2 → 6)-β-d-fructofuranose branching. DSS-induced colitis mice were used to determine the inhibitory effects of ALP-1 on gut inflammation. Results indicated that ALP-1 could significantly ameliorate the dysregulation of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) and anti-inflammatory cytokine (IL-10) caused by colitis. Besides, as compared with model group, the abundance of Firmicutes, Ruminococcaceae, Lachnospiraceae and Lactobacillus were significantly increased with ALP-1 treatment. And ALP-1 could significantly inhibit the levels of Proteobacteria, Alcaligenaceae, Staphylococcusand and Bacteroidetes. Therefore, ALP-1 may be effective in protecting mice from DSS-induced colitis.