Structural characterization of Hericium coralloides polysaccharide and its neuroprotective function in Alzheimer's disease.

Alzheimer's disease (AD) is a common neurodegenerative disorder. Polysaccharides have been scientifically demonstrated to possess neuroprotective properties. In this study, a polysaccharide was isolated from the fruiting bodies of Hericium coralloides using hot water extraction and purified using column chromatography. This H. coralloides polysaccharide (HCP) is a galactan with a main chain of →6)-α-d-Galp-(1 → and a molecular weight of 16.06 kDa. The partial α-l-Fucp-(1 → substitution takes place at its O-2 position. The neuroprotective effects of HCP were investigated in an APP/PS1 mouse model of Alzheimer's disease. The step-down and Morris water maze tests demonstrated that HCP effectively ameliorated cognitive impairment. After 8-week treatment, HCP reduced amyloid-β plaques and phosphorylated tau protein deposition. In combination with the gut microbiota and metabolites, proteomic analysis suggested that the neuroprotective effects of HCP are associated with neuroinflammation and autophagy. Immunofluorescence and western blotting analyses confirmed that HCP facilitated the polarization of M2 microglia by augmenting autophagy flux, thereby effectively reducing levels of amyloid-β plaques and neuroinflammation. These data demonstrate that HCP effectively mitigates neuroinflammation by enhancing autophagic flux, demonstrating its potential for the treatment of AD.