Structural characterization and biological activity of polysaccharides from Ganoderma lucidum cultivated under forest...

Two polysaccharides (SGLP1 and GLP1) were isolated and purified from the spore powder and fruiting bodies of Ganoderma lucidum cultivated under forest conditions. The molecular weights of SGLP1 and GLP1 were determined to be 1.97 × 10⁵ Da and 2.31 × 10⁵ Da, respectively, using size-exclusion chromatography with multi-angle light scattering. Monosaccharide composition, infrared spectroscopy, methylation, and nuclear magnetic resonance analyses revealed that SGLP1 and GLP1 primarily consisted of glucose. Notably, a rare fucose observed in G. lucidum spores powder was also identified in SGLP1. The main chain of SGLP1 was composed of β-(1,3,6) and β-(1,6) glycosidic bonds, whereas that of GLP1 consisted of β-(1,4) glycosidic bonds. Cell-based assays demonstrate that both SGLP1 and GLP1 significantly contributed with antioxidant and immune regulation, with a clear quantitative relationship between their effects; SGLP1 exhibits superior efficacy compared to GLP1. Western blot analysis demonstrates that SGLP1 activates the MAPK signaling pathway by enhancing MAPK phosphorylation. Concurrently, IκB undergoes degradation, and NF-κB was translocated to the nucleus to exert its transcriptional regulatory function, thereby modulating immune regulation. Collectively, these results establish forest-cultivated G. lucidum as a premium, sustainable source of bioactive polysaccharides, holding considerable promise for functional foods and immunoregulation.