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.