Crude Polysaccharides from Wild-Growing Armillaria mellea—Chemical Composition and Antidiabetic, Anti-Inflammatory, Antioxidant, and Antiproliferative Potential

Armillaria mellea is a commonly harvested and consumed mushroom in Poland. Several activities of polysaccharides from this species have already been reported. However, polysaccharides from A. mellea growing in the wild in Poland have not yet been investigated. This study was conducted to obtain a crude polysaccharide fraction (AmPS) and investigate its chemical composition and biological properties. Our research suggests that A. mellea is a valuable source of polysaccharides, including β-glucans. 1H NMR and high-performance capillary electrophoresis analysis of AmPS revealed the occurrence of polysaccharides consisted of myo-inositol, mannitol, fucose, galactose, glucose, and mannose. Proteins, uronic acids, and phenolics were present only in trace amounts in the AmPS. The AmPS fraction was found to exhibit strong α-glucosidase inhibitory activity; however, no activity in relation to α-amylase was detected. The fraction was also able to inhibit pro-inflammatory enzymes, i.e., lipoxygenase, cyclooxygenase, and hyaluronidase. Moderate antioxidant and antiradical activity of AmPS was revealed by the ORAC and ABTS assay, respectively. The AmPS fraction was found to have antiproliferative potential against gastric and colorectal cancer cell lines (AGS, HT-29). These findings suggest that AmPS may be considered a health-beneficial food ingredient. Since A. mellea is a commonly known edible mushroom with a long tradition of use, its polysaccharides may be considered safe components for direct consumption or production of nutraceuticals.