Medicinal Mushrooms as Sources of Immunomodulatory Polysaccharides: Extraction and Bioactivity

Abstract

Polysaccharides from medicinal mushrooms, above all beta-glucans and protein-bound glucans from shiitake, reishi, turkey tail and related species, are among the best known natural immunomodulators, and they are sold as drugs in a few countries and as supplements in many. This narrative review asks how these polymers are extracted and characterised, what the immune system appears to do with them, and how much weight the reported bioactivity can bear. It draws on published work on structure, receptor recognition, extraction technology, analytical chemistry and clinical use, and it reports no new data. Hot-water and alkaline extraction remain the workhorses, and newer ultrasound-, microwave- and enzyme-assisted methods promise gentler and faster recovery, yet every step changes the polymer that is eventually tested. Cell and animal studies show consistent activation of innate immune cells through recognised receptors, whereas clinical evidence is patchy, concentrated on a few purified products and hard to transfer to crude supplements. Poor description of the starting material, residual protein and endotoxin, and mixing of fruit body with grain-based mycelium blur many comparisons. The review concludes that immunomodulatory activity is real but conditional on the preparation, and it sets out the details a convincing report should give.