Mushrooms versus fungi: Natural compounds from Lentinula edodes inhibit aflatoxin biosynthesis by Aspergillus parasiticus

Although the strategies routinely adopted to limit production of carcinogenic aflatoxins by Aspergillus parasiticus and Aspergillus flavus in foods and feeds can be quite effective, they are often neither environmentally friendly, nor non-toxic for end users. Polysaccharides and glycoproteins, particularly beta-glucans from the basidiomycete Lentinula edodes, already known for their health-promoting effects on animals and humans, have previously demonstrated the ability to inhibit aflatoxin biosynthesis by stimulating the antioxidant defences of the toxigenic fungus. Here the results of a study regarding the influence on polysaccharide production by L. edodes of oxidative stress induced using paraquat (PQ) treatment are reported. Paraquat 0.5 and 1 mM resulted in an enhancement of the expression of the beta-glucan synthase gene Lefks1 and a consequent stimulating effect (about 30-35%) on beta-glucans production. Moreover, oxidative-stress (PQ) induced polysaccharides have a higher aflatoxin inhibiting capacity in two different strains of A. parasiticus in comparison with non-induced polysaccharides. This more efficient inhibition might be explained by a higher content of beta-glucans because (1)H-NMR analysis revealed no obvious qualitative differences between PQ-induced and non-induced polysaccharides. The results obtained show promise for improving the quantity and efficiency of L. edodes extracts in order to achieve enhanced control over aflatoxin biosynthesis in foods and feeds using health-promoting and environmentally-friendly compounds.