Structural Characterization Of Polysaccharides Of A Productive Strain Of The Culinary-Medicinal King Oyster Mushroom, Pleurotus Eryngii (Agaricomycetes), From Italy

A preliminary biological investigation of the dry basidiomata of strain C-142-c of Pleurotus eryngii has shown significant antioxidant activity. Two different polysaccharides (PEPS-A1 and PEPS-A2) were isolated from the cultivated edible mushroom, P. eryngii C-142-c strain. Based on acid hydrolysis, methylation analysis, and nuclear magnetic resonance experiments (H-1, C-13, distortionless enhancement by polarization transfer, double quantum filtered correlation spectroscopy, total correlation spectroscopy, nuclear Overhauser effect spectroscopy, heteronuclear single-quantum correlation spectroscopy, and heteronuclear multiple-bond correlation spectroscopy), the structures of the repeating unit of PEPS-A1 and PEPS-A2 were established as follows: (l)PEPS-A1 (alpha-glucan): [-> 6)-alpha-D-Glcp-(1 -> 6)-alpha-D-Glcp-(l ->](n); and (2) PEPS-A2 (beta-glucan): [-> 6)-beta-D-Glcp-(1 -> 6)-beta-D-Glcp-(1 ->](n). The antioxidant activity of PEPS-A1 and PEPS-A2 was evaluated as hydroxyl radical scavenging activity. PEPS-A1 and PEPS-A2 showed SC50 values of 400 mu g/mL and 122 mu g/mL, respectively, suggesting their possible use as a dietary supplement in functional foods. The polysaccharides were tested for their activity on cell viability using a colorectal adenocarcinoma cell line (HT-29). Both polysaccharides affected cell viability after 48 and 72 hours of treatment, inducing the death of 50% of HT-29 cells between 0.25 and 1 mu g/mL and between 0.5 and 1 mu g/mL, respectively, for PEPS-A1 and PEPS-A2. These results are promising for future applications of these mushroom-derived polysaccharides as antioxidants and antitumor agents.