Galactomannans with novel structures from the lichen Roccella decipiens Darb Original Research Article

Two homogeneous galactomannan fractions were isolated from the lichen, Roccella decipiens, one (FP) containing Man and Gal in an 81:19 molar ratio and the other (RFS), having Man, Gal, and Glc in a 43:56:1 molar ratio. FP consisted of a main chain with (1→4)-linked α-d-Manp units, most of which were substituted at O-2 with side chains consisting of nonreducing end-, 2-O- and 6-O-substituted α-Manp units. The latter appeared to be substituted by single-unit β-d-Galf nonreducing ends. RFS contained a similar α-d-Manp core structure, but with side chains containing nonreducing end, 5-O-, 6-O-, and 5,6-di-O-substituted β-d-Galf units. Such polysaccharide structures have not been previously reported.