Rhizoctonia solani fucomannogalactan: Chemical characterization and antiproliferative activity

Abstract A fucomannogalactan from Rhizoctonia solani biomass was obtained after hot aqueous extraction and purified by freeze-thaw cycles and gel filtration chromatography on Sepharose CL-6B. The polysaccharide was homogeneous after HPSEC/RID analysis (M w /M n  ~ 1.1), displaying an average molecular weight of 15.4 × 10 3  Da. Its chemical structure was determined by methylation analysis (GC/MS) and spectroscopy (FTIR, 1D and 2D NMR). The polysaccharide had a branched α-1,6-linked Gal p backbone with 66% linear residues, a number of which were at O -3 methylated. Side chains (34%) were always linked at O -2 positions of the main chain and consisted of single, non-reducing ends of α- d -Man p (6%) and α- l -Fuc p (28%). Analysis of its biological activity showed that the highly purified fucomannogalactan from R. solani inhibited the proliferation of colon cancer cells in vitro , but that it did not have the same activity against lung cancer cells.