Naturally methylated mannogalactans from the edible mushrooms Pholiota nameko and Pleurotus eryngii

This study reports the presence of mannogalactans in Pholiota nameko and Pleurotus eryngii edible mushrooms, with their purification and detailed structural characterization. Two mannogalactans (R30PN and E30PN) were reported in P. nameko, differing mainly in their Mw (37.9 x 104 g/mol and 2.4 x 104 g/mol). The mannogalactans presented a linear (1 -> 6)-alpha-D-galactan in the main chain, and single branches at O-2 by beta-D-Manp as non-reducing end units. The main chain also contained naturally 3-O-methylated Galp units, in amounts that varied from 15.2-23.7 %. P. nameko mannogalactans were described for the first time. Heteropolysaccharides from mushrooms may display functional activities, like antitumor, anti-inflammatory and immunostimulatory which are related to their chemical structure. Thus, this study is of relevance since it unveils the structural details of two mannogalactans from P. nameko and one from P. eryngii mushrooms. Further studies are encouraged to verify how these structural differences may interfere in their biological activities.