Structural Characterization of a Pleurotus sajor-caju Polysaccharide and Its Neuroprotection Related to the Inhibition of Oxidative Stress

A novel polysaccharide PSP2-1 was isolated and purified from Pleurotus sajor-caju. The structural characterization data displayed that the molecular weight of PSP2-1 was 44.9 kDa, and PSP2-1 consisted of fucose, galactose, glucose, and mannose. The methylation results showed that the glycosidic bonds of PSP2-1 included T-Fuc, 1,6-Gal, T-Glc, 1,6-Glc, 1,3,6-Glc, 1,3-Man, 1,2,6-Man, and T-Man. Neuroprotective studies indicated that PSP2-1 significantly improved the cell viability of the H2O2-induced oxidatively damaged neuronal cell HT22, reduced the release of LDH, inhibited apoptosis and release of cytochrome c, and alleviated the decline of mitochondrial membrane potential and ROS accumulation. Furthermore, PSP2-1 decreased the phosphorylation levels of cleaved PARP and cleaved caspase-3, and increased the ratio of bcl-2/bax. Additionally, PSP2-1 could inhibit the phosphorylation of MAPK family members including JNK, p38, and Erk. Finally, animal experiments showed that PSP2-1 could improve the oxidative stress injury and the learning and memory ability of mice with aging induced by D-galactose. Our results confirmed that PSP2-1 significantly ameliorated the oxidative stress injury, inhibited the apoptosis in H2O2-induced neuronal cells via MAPK pathway, and also improved cognition in mice with aging induced by D-galactose. Our research gives the foundation for the functional food application of P. sajor-caju polysaccharides in the future.