Abstract

Understanding how molecular architecture dictates the bioactivity of functional oligosaccharides remains a major challenge. Here, mannan oligosaccharides (MOS) were prepared from yeast cell wall mannan, and Gleditsia sinensis Lam. endosperm galactomannan, to investigate structure-function relationships in preventing inflammatory bowel disease. The protective effects of yeast-derived MOS (Y-MOS) and Gleditsia-derived MOS (G-MOS) were comparatively evaluated using a dextran sodium sulfate (DSS)-induced colitis mice model. Structural analysis revealed that Y-MOS primarily consisted of α-1,6 linked mannose with α-1,2/α-1,3 linked side chains, whereas G-MOS featured a β-1,4 linked mannose backbone with α-1,6 linked galactose branches. Furthermore, both MOSs mitigated colitis symptoms, preserved colonic epithelial barrier integrity, and suppressed inflammatory cytokines, primarily through suppressing JAK2-STAT3 and NF-κB signaling pathways, regulating gut microbiota, and promoting short-chain fatty acid production. Notably, G-MOS was more effective than Y-MOS, particularly in immune regulation and modulation of gut microbiota. Molecular docking further revealed that the rigid β-linked conformation of G-MOS exhibited stronger binding affinity toward inflammatory receptors, leading to more effective pathway inhibition, as validated in LPS-treated RAW264.7 cells. These findings elucidate a glycosidic topology-dependent molecular mechanism underlying MOS bioactivity, and identify β-linked G-MOS as a promising, sustainable candidate for inflammation management.