Structural Characterization and Immunobiological Activity of Polysaccharides from Astragalus Oyster Mushroom

Abstract

When added to mushroom growing substrates, edible and medicinal herbs affect the mushrooms’ nutritional and medicinal value. In this study, polysaccharides (P0OP-I and P15OP-I) were extracted and purified from oyster mushrooms grown on substrates supplemented with 0% and 15% Astragalus roots (P0 and P15), respectively, and their chemical structure and immunobiological activities were compared. P15OP-I and P0OP-I were extracted using ultrasound-assisted hot water and deproteinized with the Sevage method, depigmented with 30% H2O2, desalted with dialysis, and purified using DEAE-52 cellulose and Sephadex G-100 dextran column chromatography. The molecular weight of P0OP-I and P15OP-I was 21,706.96 and 20,172.65 Da, respectively. Both were composed of monosaccharides D-mannose, galacturonic acid, D-glucose, D-galactose, and L-arabinose but in different molar ratios, and both were connected by a pyranoside linkage. P15OP-I consisted of higher contents of mannose, glucose, galactose and arabinose and lower content of galacturonic acid as compared to P0OP-I. Both P0OP-I and P15OP-I induced NO and TNF-α production but did not show cytotoxic effect or induce ROS generation in RAW264.7 cells. P15OP-I showed a stronger ability to promote NO and TNF-α production relative to P0OP-I. In vitro experiments showed that the immunomodulatory activity of P0OP-I and P15OP-I in RAW264.7 macrophages were mediated by the JNK/MAPK, Erk/MAPK, and NF-κB signaling pathways. The results would be helpful for elucidation of the health promoting mechanism of Astragalus oyster mushrooms as a source of neutraceuticals.