From six species of lichens, a variety of polysaccharide fractions were prepared and their antitumor effects were tested against the sarcoma 180 implanted in mice. These fractions were characterized by chemical and physicochemical methods. The active principle of Lasallia pensylvanica has been determined as GE-3 type glucan (a partially O-acetylated β-(1→6)-glucan). Another highly effective β-glucan, containing (1→3)-and (1→4)-linkages in the ratio 3 : 7, was isolated from Usnea rubescens, and it has been identified with lichenin. In addition, presence of so far unknown heteropolysaccharides with moderate antitumor effect has been suggested in the minor fraction of the lichen. Four Cladonia lichens, i.e.C. crispata, C. mitis, C. rangiferina subsp. grisea, and C. squamosa, were also examined, and it has been revealed that, in all of them, complex heteroglycans consisting chiefly of mannose, galactose, and glucose occur commonly as predominant, cold-water soluble polysaccharides, together with a small amount of α-glucan presumed to be PC-3 type (an α-glucan possessing (1→3)- and (1→4)-linkages alternately). Both the heteroglycan fraction and the glucan fraction of C. squamosa were shown to exert moderate antitumor effect.
