Structural Elucidation and Anti-inflammatory Activity of Neutral Polysaccharide from <italic>Orchis chusua</italic> D. Don

To systematically investigate the structural features and anti-inflammatory activity of neutral polysaccharide (USP-N) from Orchis chusua D. Don, a medicinal and edible plant was selected. The structure of USP-N was comprehensively elucidated through partial acid hydrolysis, Smith degradation, methylation analysis, and 2D-NMR spectroscopy. Its anti-inflammatory effects were evaluated using a zebrafish inflammation model. Structural analysis revealed that the main chain of USP-N was composed of alternating β-1,4-linked glucose (38.5%) and mannose (33.8%), forming a glucomannan backbone. The side chains contained small amounts of rhamnose, arabinose, and galactose, with some mannose residues featuring 2-O-acetyl groups. Bioactivity assays demonstrated that USP-N treatment significantly suppressed LPS-induced nitric oxide (NO) release (PPOrchis chusua D. Don polysaccharides in functional foods and pharmaceutical development.