Characterization and β-secretase Inhibitory Activity of Water-soluble Polysaccharides Isolated from Phellinus linteus Fruiting Body

A key molecule in the pathogenesis of Alzheimer`s disease (AD) is the -amyloid peptide () generated by -secretase activity, an aspartic protease. This study was designed to evaluate inhibitory effect of the high-molecular weight water-soluble polysaccharides (Et-P) isolated and purified from Phellinus linteus fruiting body on -secretase activity. The Et-P was purified from the hot water extract of Phellinus linteus fruiting body mainly by 75% ethanol precipitation and DEAE-Cellulose column chromatography. From the DEAE-Cellulose chromato-gram and molecular weight analysis, the Et-P was shown to be a mixture of three polysaccharides with molecular mass of 1,629, 1,294, and 21 kDa, respectively. The monosaccharide composition of Et-P was determined to be glu-cose, galactose, and mannose as major sugars, glucose being the most prominent one (48% in mole percentage). The elemental analysis and FT-IR analysis suggested that Et-P is typical polysaccharides having at least partially -linkages and possible existing as complex with phenolic compounds. The laminarinase digestion and HPAEC-PAD analysis suggested that Et-P is a variant of beta-(1,3)-glucans. The Et-P showed DPPH radical scavenging activity and, especially, a significant inhibitory activity on -secreatase activity (48% inhibitin at 100 ), suggesting that they may inhibit the formation of which is the major causative of Alzheimer`s disease. The results of this study suggest that the water soluble polysaccharides of Phellinus linteus fruiting body can be a potent material for the development of preventive or therapeutic agents for AD.