Pretreatment, physicochemical analysis and structure–activity relationships of antioxidant activities of nine edible mushroom polysaccharides

BACKGROUND: Commercially available edible mushroom polysaccharide (EMP) products often contain impurities such as maltodextrin, proteins and polyphenols, which interfere with accurate quality evaluation. This study aimed to establish a pretreatment protocol to purify these products and investigate the structure-activity relationships of their antioxidant activities. RESULTS: Physicochemical analysis revealed that maltodextrin interfered with polysaccharide quantification. A pretreatment protocol using glucoamylase for maltodextrin removal and potassium ferrocyanide/zinc acetate for deproteinization was optimized. The purified crude polysaccharides were heteroglycans with broad molecular weight distributions. All nine EMPs exhibited antioxidant capacity, with Grifola frondosa (Dicks.) Grey polysaccharide and Cordyceps militaris (L.ex Fr.) Link polysaccharide showing the most potent activities. Structure-activity relationship analysis indicated that antioxidant activity was positively correlated with the contents of mannose, galactose, arabinose, fucose and uronic acid. CONCLUSION: The proposed pretreatment reduced interference from starch-based substances and proteins in the tested commercial products. Residual protein and phenolic-compound contents were associated with several in vitro antioxidant indicators, suggesting that coexisting components may influence the measured responses. This study provides a theoretical basis for elucidating the antioxidant mechanisms of polysaccharides and highlights the need for standardized pretreatment in quality evaluation. © 2026 Society of Chemical Industry.