IMMUNOLOGICALLY ACTIVE POLYSACCHARIDE FROM CETRARIA-ISLANDICA

A new alkali-soluble polysaccharide has been isolated from Iceland mos s, Cetraria islandica (L.) Ach., by ethanol fractionation, ion-exchang e chromatography, and gel filtration. The mean M(r) was estimated to b e 18,000. Sugar and methylation analysis, partial hydrolysis, and C-13 -NMR spectroscopy showed the polysaccharide to be a branched galactoma nnan with a backbone composed of two structural elements; (1-->6)-link ed alpha-D-mannopyranosyl and alpha-D-(1-->6)-galactopyranosyl units. The polysaccharide showed pronounced immunostimulating activity in an in vitro phagocytosis assay and in the in vivo carbon clearance assay.