Investigation of the mechanism of selenium incorporation into the structure of exopolysaccharides of fungal origin and the impact of this phenomenon on their biological activity.

The increase in the incidence of malignant neoplasms made it necessary to look for means saving the lives of patients. The interest of scientists was aroused by mushroom extracts, which have been used in the Far East for 2,000 years as alternative components of natural medicine. Currently, research is conducted on the antitumor and immunomodulatory activity of polysaccharides of fungal origin. Conclusions resulting from the analysis of research works of these compounds are promising, because several isolates, derived from the mycelium or fruiting bodies of fungi belonging to the Basidiomycota type, have been approved for treatment in some countries as dietary supplements and as an anti-cancer drug. In Japan, lentinan, a licensed anti-cancer drug that has been used since 1985 by the Japanese pharmaceutical company Ajinomoto, remains in the top ten of the most used anticancer drugs. Lentinan is a highly purified exopolysacchardide fraction, showing a high level of immunomodulatory activity. It was first isolated in 1970 by Chihara from Lentinula edodes (Shii-take mushroom) and is still extracted by the same method to this day. Unfortunately, the cultivation time of L.edodes fruiting bodies is relatively long, and the complex isolation procedure results in low yield and a very high price of the obtained medicinal preparation. Selenium also has an anti-cancer effect. A similar pharmacological effect caused by polysaccharides of fungal origin (β-glucans) and selenium compounds, despite the difference in the mechanism of action, suggests a synergism of both components. Selenium added to the medium may increase the immunomodulatory effect of polysaccharides from the culture medium. The aim of the project is to investigate the mechanism of selenium incorporation into the structure of exopolysaccharides secreted into the substrate in submerged culture of mycelium of the medicinal fungus Lentinula edodes in a liquid medium enriched with sodium selenate (IV) and to determine the impact of this process on the biological activity of these compounds. The project foresees to compare the structure of the intended selenium ego-polysaccharide fractions with reference fractions isolated from non-selenium enriched culture. The research carried out in the project should answer the following questions:

• Does the incorporation of selenium into the structure of exopolysaccharides affect the immunomodulatory, cytotoxic and antioxidant activity of the fraction?

• What is affected by the binding of immune system receptors to β-glucans?

• Could L.edodes breeding in the future contribute to the design of an immunomodulatory drug that would be much cheaper and less toxic than those available on the pharmaceutical market today?