STRUCTURAL STUDY OF POLYSACCHARIDES FROM OAK LICHEN EVERNIA PRUNASTRI (L) ACH .I. AN ALKALI-SOLUBLE GALACTOMANNAN

An acidic galactomannan, [α]20D +79% (water), containing d-galactose (36%), d-mannose (54%), and d-galacturonic acid (10%) has been extracted with dilute alkali from the oak lichen Evernia prunastri (L) Ach. Hydrolysis of the fully methylated galactomannan yielded 2,3,4,6-tetra-O-methyl-d-galactopyranose (3.2 mol.), 2,3,4,6-tetra-O-methyl-d-mannopyranose (1 mol.), 3,4,6-tri-O-methyl-d-mannopyranose (1.1 mol.), 3,4-di-O-methyl-d-mannopyranose (1.1 mol.), 3,5-di-O-methyl-d-mannofuranose (0.9 mol.), 4-O-methyl-d-mannopyranose (1.2 mol.), and 2,3,4-tri-O-methyl-d-galacturonic acid (1 mol.). Since the results of periodate oxidation and Smith degradation were in agreement with methylation studies, it was concluded that the heteroglycan is a highly branched, acidic galactomannan, containing a basic chain of (1→2)- and (1→6)-linked mannose residues. The galactopyranose and galacturonic acid residues are present exclusively as non-reducing, terminal groups. On the basis of i.r. spectral data and enzymic hydrolysis, the galactopyranose residues are assigned the β-d configuration, whereas the mannose residues appear to be predominantly of the α-d type. © 1969.