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.