Isolation and characterization of immuno-stimulating polysaccharide in Korean black raspberry wine

Abstract

To characterize polysaccharides existing as soluble form in Korean fruit wines, polysaccharides were isolated from Korean black raspberry wine, and their immuno-stimulating activities were examined. A complex pectic polysaccharide, RB-2 was purified from the crude polysaccharide (RB-0) in raspberry wine by subsequent size-exclusion chromatography. RB-2 had relatively potent macrophage activity and splenocyte mitogenic activity in vitro. The intravenous administration of RB-2 significantly augmented the cytotoxicity of natural killer cells against Yac-1 tumor cells. RB-2 consisted of 15 monosaccharides including rarely observed sugars in general polysaccharides, such as 2-O-methyl-fucose, 2-O-methyl-xylose, apiose, aceric acid, 3-deoxy-D-manno-2-octulosonic acid, and 3-deoxy-d-lyxo-2-heptulosaric acid. Methylation analysis indicated that RB-2 comprised at least 20 different glycosyl linkages such as 3,4-linked fucose, 2,3,4-linked rhamnose, 3′-linked apiose, and 2,3,3′-linked apiose, characteristic of rhamnogalacturonan II (RGII). RB-2 was eluted as two peaks having a high (9,000 Da) and a low molecular mass (5,000 Da) on high performance size exclusion chromatography, and the peak of high molecular mass was down shifted to the low molecular mass under the acidic pH conditions less than 2.0. Results indicated higher molecular weight polysaccharide in RB-2 was mainly presented as an RG-II dimer, and Korean black raspberry wine contains selected polysaccharides, which provide immunostimulating activities beneficial to human health.