Dietary polysaccharide extracts of Agaricus brasiliensis fruiting bodies: chemical characterization and bioactivities at different levels of purification

Abstract

Polysaccharides of the European strain of A. brasiliensis were obtained by hot water extraction and ethanol precipitation (HWPE I) of fruiting bodies, and further purified by dialysis (HWPE II) and pronase incubation (PPE). These polysaccharides consisted mainly of (1 -> 6)-beta-D-glucans. PPE was free of proteins and polyphenols as demonstrated by quantitative assays and NMR profiling. They showed a clear IFN-gamma inducing activity in human PBMCs, which suggests these polysaccharides to have proinflammatory effects. Treatment by beta-glucosidase caused the polysaccharides to be degraded into smaller fragments and at the same time increased their IFN-gamma inducing activity in PBMCs fourfold. In vitro, PPE showed a dose-dependent inhibition of the proliferation of the human leukemia Jurkat cell. At 100 mu g/mL the cells' viability was decreased by appr. 51% compared to the control. EPR spin trapping demonstrated a high antioxidative activity against (OH)-O-center dot and (center dot)O2(-) radicals of HWPE land PPE. Further, the results of the antioxidant assays indicated that antioxidant activity against (OH)-O-center dot radicals in the Fenton system was achieved through scavenging or through chelating iron mechanisms. The good immunomodulating and antioxidative properties of A. brasiliensis polysaccharide extract obtained by hot water extraction and ethanol precipitation make it suitable for everyday use as an inexpensive dietary supplement.