Edible mushroom polysaccharides: Structural characteristics, chemical modification strategies, and structure-activity relationship: A review

Edible fungal polysaccharides (EFPs) are emerging bioactive macromolecules, with 4545 articles published from 2014 to 2024 and over 118,000 citations. However, their structure-activity relationship (SAR) remains inadequately defined, and the effects of extraction and chemical modification require systematic evaluation. This review summarizes the structural features of EFPs-including α-/β-glucans, heteroglucans, galactans, and mannans-and explores how molecular weight (1.27-5420 kDa), monosaccharide composition, glycosidic linkage patterns, branching, and spatial conformation influence bioactivity. β-(1 → 3)-glucans with β-(1 → 6) branches and triple-helix conformations show strong immunomodulatory effects, while low-molecular-weight fractions (<50 kDa) enriched in uronic acids exhibit enhanced antioxidant activity. Medium-weight polysaccharides (100-500 kDa) act via dectin-1 and Toll-like receptors. Chemical modifications-such as sulfation (DS 1.5-2.0), acetylation, carboxymethylation, selenylation, and phosphorylation-further enhance bioactivities. For example, selenylated EFPs improved zeta potential by 69.12 % and exhibited dose-dependent antitumor effects, while phosphorylated derivatives showed enhanced anti-inflammatory activity. The review highlights critical challenges in extraction standardization and quality control. Integration of advanced analytical techniques (e.g., HPSEC-MALLS, 2D-NMR, AFM) enables atomic-level characterization. Future directions include site-specific modification, machine learning-driven SAR prediction, and sustainable design strategies. This work provides a mechanistic foundation for the rational development of EFP-based therapeutics targeting immunity, metabolism, and gut microbiota.