Heterogalactans obtained from some typical edible mushrooms

Abstract

Eight distinct heterogalactans were extracted with 3% trichloroacetic acid followed by fractional alcoholic precipitation with methanol and Cetavlon from 8 species of Japanese edible mushrooms (Flammulina velutipes, Hypsizigus marmoreus, Pleurotus ostreatus, Pleurotus eryngii, Agaricus bisporus, Agaricus blazei, Grifola frondosa, Hericium erinaceum). On complete acid hydrolysis of these heterogalactans, D-galactose, D-mannose, and L-fucose were confirmed as common constituents. By applying partial acid hydrolysis, galactobiose and galactotriose were identified. These results reveal that all of these heterogalactans should contain α-1,6 linked D-galactan backbone. The molar-ratio of component sugars in each heterogalactans was quite different from species to species. In aspect of the molar-ratio of component sugars, we classified these heterogalactans into following 4 types. Type 1 : fucose free, mainly contain mannogalactan ; Type 2 : mannose and fucose-rich (each 30-60% of galactose content) ; Type3 : intermediate amount of fucose (10-20% of galactose content) and intermediate amount of mannose (5% of galactose content) ; Type 4 : mannose free, mainly contain fucogalactan. Though we could not detect type 4 in Agaricales, another type of heterogalactans ; type 1 was not detected in Aphyllophorales.