ISOLATION AND CHARACTERIZATION OF A RHAMNOGALACTURONAN-II FROM RED WINE

A complex polysaccharide originating from grape was purified from a red wine by size-exclusion and ion-exchange chromatography. This polysaccharide contained 2-O-methylfucose, rhamnose, fucose, 2-O-methylxylose, arabinose, apiose, galactose, galacturonic and glucuronic acids, and thiobarbituric acid assay-positive material, presumably 3-deoxy-D-manno-2-octulosonic acid (Kdo) and 3-deoxy-D-lyxo-2-heptulosaric acid (Dha). Methylation structural analysis showed that this polysaccharide is a typical rhamnogalacturonan II (RG-II), a structurally complex pectic polysaccharide that has been isolated previously from the primary cell walls of sycamore. Red wine RG-II presented discrete differences from previously described RG-II's, a greater richness in uronic acids and some additional glycosyl linkages, which might be related to the pattern of degradation of grape-wall pectic substances by endogenous pectinolytic enzymes after pressing the berries and subsequent fermentation to wine.