beta-Glucans are an important contributor to the biological activity of medicinal mushrooms including Reishi, Shiitake and Maitake. However, measuring the level of glucans is complicated by their molecular size, structural diversity, solubility and linkage specificity between alpha- and beta-glucans. The latter is important in assessing mushroom quality, as they are inherently low in alpha-glucans and rich in 1,3:1,6-beta-glucans. Enzymatic analysis of beta-glucans in mushrooms has become an accepted method of choice, however it has limitation with formulated products. An alternative is through bioassays that focus on immunomodulatory effects by quantifying the expression of cytokines in immune cells.
Nine different mushroom powders and extracts (0.1 mg/mL) were assayed for their effects on a suite of cytokines (IL-1alpha , IL-6 and TNF-alpha ) in human macrophages (+/- LPS stimulation). We found with the exception of IL-1alpha, cytokine expression was up regulated for the majority of samples. That is, both TNF-alpha and IL-6 were up regulated in non-LPS-stimulated macrophages and for the most part up regulated for the majority of extracts and powders in LPS-stimulated macrophages. Some variation in cytokine expression was evident between the mushroom powders and extracts. We therefore determined the alpha- and beta-glucan content to assess if this correlated with cytokine expression.
beta-Glucan content across nine different samples ranged from 8-40% whilst the alpha-glucan content was lower (0.75-13.8%). A suite of growth media and formulation excipients invariably led to interferences with the glucan data. An inverse correlation between IL-1alpha expression and beta-glucan content was observed, however the correlations were inconsistent across the other cytokines monitored. Our data suggests that further investigations are essential to characterise the structural diversity of beta-glucan rich medicinal mushroom products, particularly with respect to detailed beta-glucan composition and how this correlates with specific immuno-modulatory responses.