Two Mycopolysaccharides from Hirsutella sinensis mycelia: Structural characterization and dual antioxidant-cardioprotective functions.

Cordyceps sinensis, a precious traditional Chinese herb, exhibits diverse polysaccharide structures and functions across strains. This study screened Hirsutella sinensis 02-3 and successfully extracted two mycopolysaccharides (fungal polysaccharides): ISP-AII (MW = 4.70 kDa) and ISP-BII (MW = 75.42 kDa). Chemical and monosaccharide composition analyses showed that ISP-AII comprised glucose, xylose, arabinose, galactose, and mannose (molar ratio 58.39:2.63:1.21:1.03:0.99), while ISP-BII contained additional fucose and exhibited a molar ratio of 57.82:1.07:1.06:0.39:0.37:0.32 for glucose, xylose, galactose, arabinose, fucose, and mannose, respectively. Techniques such as the Congo red test, Fourier transform infrared (FTIR), Scanning Electron Microscopy (SEM), and Nuclear Magnetic Resonance (NMR) were employed to characterize their structural features, suggesting both ISP-AII and ISP-BII were →4)-α-D-Glcp-(1 → main backbone. Functionally, ISP-BII had the highest 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) scavenging rate of 61.7 %, and ISP-AII scavenged 56.12 % of hydroxyl radicals. Both also showed high reducing power and reactive oxygen species (ROS) - scavenging ability. Moreover, they protected cardiomyocytes from apoptosis by regulating key factors in the Phosphatidylinositol 3-Kinase/Protein Kinase B (PI3K/AKT) and mitochondrial BAX/Bcl-2/Caspase-3 apoptotic signaling pathways, and exerted antioxidant effects via the Keap1/Nrf2/ARE pathway. These results offer new insights into the cardioprotective functions of Cordyceps polysaccharides, and their potential applications in food, cosmetics, and pharmaceutical industries.