Maitake is increasingly being recognized as a potent source of polysaccharide compounds with dramatic health-promoting potential. Maitake's main active constituent is the polysaccharide B-(1, 6)-glucan.D-fraction is a derivative of the high molecular weight polysaccharides of Maitake (1, 000K Da m.W.) that is acid-insoluble, alkali-soluble and hot-water extractable.Both terms can be used interchangeably. D-fraction is composed of B-(1, 3) glucan branched with B-(1, 6) glucosides which is believed to be responsible for many health benefits of Maitake.