Isolation, Purification, and Characterization of Lentinus edodes Polysaccharides Extracted with Subcritical Water Enhanced with Deep Eutectic Solvent

The Lentinus edodes polysaccharide (LEP) was extracted with a new subcritical water extraction (SWE) enhanced with deep eutectic solvent (DES) method and then purified with a DEAE-52 cellulose column and a Sephadex G-100 column. Two purified polysaccharides (LEP1 and LEP2) were obtained and their structure, antioxidant activity, and immunomodulatory activity were analyzed. LEP1 and LEP2 were composed of mannose, glucose, and galactose with a molar ratio of 1:12.97:7.84 and 1:51.18:5.29, respectively. The molecular weights were 9.878×104 Da and 1.976×104 Da, respectively. Interestingly, both LEP1 and LEP2 were mainly composed of →4)-β-D-Glcp-(1→, →6)-β-D-Glcp-(1→ and →6)-α-D-Galp-(1→ with different molar ratio. Besides, both LEP1 and LEP2 had strong DPPH free radical scavenging activity and Fe2+ chelating capacity. Moreover, they could reduce the level of ROS and regulate the activities of MDA, CAT, and SOD in HepG2 cells, demonstrating strong antioxidant activity. Furthermore, both LEP1 and LEP2 could improve the phagocytic capacity, NO release, and the content of IL-6, IL-1β, and TNF-α in RAW264.7 cells, exhibited significant immunostimulatory activity. It was worth noting that LEP2 exhibited stronger biological activities than LEP1. Therefore, the SWE enhanced with DES is an ideal method for extracting polysaccharides, which can be further applied to extract other polysaccharides.