Glucan Type Polysaccharides From Lentinus Edodes: Extraction, Purification And Structural Analyses

Polysaccharides represent a structurally diverse class of macromolecules of widespread occurrence in nature and offer highest capacity for carrying biological information because they have the greatest potential for structural variability.Four polysaccharides,named LE-IP,LE-MGG;I-WCP and S-ACP,were extracted and isolated from the fruiting body of Lentinus edodes,via hot-water and alkaline extractions, then were subjected to freeze-thawing,and gel permeation chromatography(GPC).The structural investigation was studied by high performance liquid chromatography (HPLC),high performance size exclusion chromatography(HPSEC);periodate oxidation, nuclear magnetic resonance spectroscopy(¹³CNMR and ¹H NMR spectroscopy) and infrared spectroscopy(IR).Monosaccharide analysis indicated that LE-IP,LE-MGG,I-WCP and S-ACP contained glucose as their main component(99.3%,75.9%,82.9%and 92.5%respectively) besides mannose,galactose,xylose,rhamnose and uronic acids.Thus all these polysaccharides were of the glucan-type.S-ACP contained Glc(925%),Gal(6.2%) and Man(1.3%),it was soluble in water and heterogeneous on gel permeation chromatography(GPC).I-WCP contained Fuc(1.1%),Gal(7.9%),Glc(82.9%),Man(7.2%) and GlcUA (0.9%);it was slightly soluble in water and heterogeneous on GPC.LE-MGG contained Man(6.9%),Gal(15.9%) and Glc(75.9%) in a ratio of 0.1:0.2:1.0.It was soluble in water and homogeneous on GPC.Based on IR spectroscopy,¹H NMR spectroscopy and ¹³C NMR spectroscopy analyses,LE-MGG was found to be a mannogalactoglucan with a main chain of(1→6)-linked-α-D-glycopyranosyl units,partially substituted by units ofβ-D-Manp orβ-D-Galp side chains.Its molecular weight was estimated to be 5.25×10³ Da.LE-IP contained exclusively glucose as monosaccharide component.On the basis of periodate oxidation,IR spectroscopy,¹H NMR spectroscopy and ¹³C NMR spectroscopy experiments,LE-IP was found to be a water-insoluble branched(1→3),(1→6)-linkedβ-glucan, substituted by unitβ-Glcp side chains.Its molecular weight was estimated to be higher than 500 kDa. The new polysaccharide fractions,LE-IP(a branched water-insoluble(1→3)-β-D-glucan) and LE-MGG(a branched water-soluble heteroglucan),which have been isolated and characterized in this work,are of great interest due to their possible ability to act as biological response modifiers in biochemical reactions.