Two Levan-type fructans from Allium macrostemon Bunge alleviate dextran sulfate sodium-induced intestinal injury in Drosophila melanogaster.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease for which current therapies remain limited by incomplete responses, disease relapse, adverse effects, and high treatment costs. Accordingly, the development of safe and effective natural bioactive compounds has attracted increasing interest. Two polysaccharides, designated AMP80-1 and AMP80-2, were isolated and purified from Allium macrostemon Bunge. AMP80-1 (6276 Da) and AMP80-2 (13,168 Da) were determined to be levan-type fructans, which were composed of the following sugar residues: β-D-Fruf-(2→, →1)-β-D-Fruf-(2→, →6)-α-D-Glcp-(1→, →6)-β-D-Fruf-(2→, and →1,6)-β-D-Fruf-(2→. Both fructans significantly alleviated intestinal barrier leakage and midgut shortening, suppressed excessive expansion of intestinal stem cells (ISCs) and enteroblasts (EBs), reduced intestinal epithelial cell death and apoptosis-associated DNA fragmentation, and attenuated intestinal oxidative stress. Direct comparisons showed that AMP80-1 exerted significantly greater effects than AMP80-2 on midgut length, 7-aminoactinomycin D (7-AAD) fluorescence, and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) fluorescence, whereas no significant between-group differences were observed in Brilliant Blue accumulation, ISC/EB abundance, or dihydroethidium (DHE) fluorescence. Further reverse transcription quantitative PCR (RT-qPCR) analysis showed that AMP80-1 attenuated dextran sulfate sodium (DSS)-induced increases in p38b, bsk, upd1, upd2, upd3, and Stat92E expression, suggesting an association with attenuated p38/JNK-related epithelial stress and restrained Upd/JAK/STAT-associated regenerative responses. Overall, these findings demonstrate that AMP80-1 and AMP80-2 protect against DSS-induced intestinal injury in D. melanogaster and provide preliminary evidence that molecular size and fine structural differences may influence the intestinal protective activity of A. macrostemon fructans.