Evaluation of an Antioxidative Polysaccharide Fraction from Russula pseudocyanoxantha, a Novel Mushroom, as a Strategy to Enhance Innate Immunity

With a long history of appreciation as a health-beneficial food, our team has recently discovered Russula pseudocyanoxantha, which displays the presence of water-soluble bioactive polysaccharides. As part of our continuing interest in searching compounds from traditional yet unexplored food, the present research was conducted to harness the residual components by subjecting them to a hot alkali solution, yielding a bioactive rich fraction (RP-HAP). Chemical analysis unveiled that this β-glucan-enriched extract consisted of a homogeneous polymer with Mw of ~111.25 kDa. RP-HAP exhibited significant antioxidant properties, manifesting through multiple mechanisms such as inhibition of radical generation, chelating abilities, and electron donation capacity, where EC50 values ranged from 1193 to 1683 µg/mL. Moreover, RP-HAP demonstrated its potential by promoting various immune responses in RAW264.7 macrophage cells within 24 h, including cell proliferation, phagocytosis, pseudopod formation, oxidative burst, and NO synthesis. This heightened cellular activity was supported by increased expressions of key immune-related genes, such as TLR-2, TLR-4, NF-κB, iNOS, TNF-α, COX-2, IFN-γ, and Iκ-Bα underlining robust immune-boosting properties of the fraction mediated through TLR/NF-κB pathway. Thus, further exploration of RP-HAP may hold promise for the development of potent pharmaceuticals that will contribute to a healthier future for humanity.