Comparative chemical and biological investigations of β-glucan-containing products from shiitake mushrooms

Extracts from Shiitake mushrooms (SME) are promoted for health claims, especially for their immunomodulatory effects but references reveal that contamination with bacterial lipopolysaccharides may provide false positive results. Therefore, we characterised chemical and biological aspects of commercial and experimental SME. Pure β-glucan and lipopolysaccharide served as controls. Commercial SME were contaminated with endotoxins and β-glucan contents strongly depended on the used chemical-analytical method and varied between SME. The tested SME did not show signs of cytotoxicity and genotoxicity and have no influence on function of human lymphocytes, whereas endotoxin-free SME stimulated distinct cytokine patterns of human monocytes. Clear correlation between β-glucan content and immunological effects could not be found. Exclusion of endotoxin contamination is obligatory for in vitro biological activity testing of SME. Polysaccharide or β-glucan content does not predict biological activity but interleukin-8 production of monocytes is a suitable in vitro-system for detection of immunomodulatory effects of SME.