Polysaccharide extracts from mycelia of Ganoderma australe: effect on dendritic cell immunomodulation and antioxidant activity

Abstract

Many fungi have inner-polysaccharides (IPS) that can modulate the immune response and/or have antioxidant activity. Ganoderma australe, a species from Patagonia, is a likely candidate to produce bioactive IPS. Our aims were to assess the ability of its IPS to induce maturation and activation of dendritic cells (DCs), to determine their antioxidant activity, and to evaluate the influence of the chemical composition on the bioactivity of the IPS. Mycelia were cultivated in different liquid culture media (M1, M2, and AG), and polysaccharides were extracted with hot water. Mice bone marrow-derived DCs were exposed to the different IPS, and the percentage of cells expressing CD86, MHC II, and IL-12 was determined. The antioxidant activity was evaluated through four assays. Results showed that the chemical composition of the three extracts was different. Glucose, mannose, and galactose prevail in all the extracts, although in different proportions. IPS from mycelia growing in M1 (IPS_M1) significantly increased the expression levels of MHC II and CD86 in a concentration-dependent manner, and the same tendency was found for IL-12 production. This IPS extract was mainly composed of glucose. Only IPS obtained from mycelia growing in M2 (IPS_M2) showed significant antioxidant activity, possibly related to the presence of a greater amount of phenolic compounds in this extract. This is the first study reporting the ability of aqueous extracts of mycelial polysaccharides from G. australe to maturate and activate mouse DCs, as well as to prevent oxidation, encouraging further studies of the immunomodulatory and antioxidant effects of these compounds.