Structure of a sulfated xylogalactan from the calcareous red alga Corallina pilulifera P. et R. (Rhodophyta, Corallinaceae)

Abstract

The structure of a sulfated polysaccharide isolated from the calcareous red alga Corallina pilulifera was studied by methylation analysis before and after desulfation or Smith degradation, as well as by 1D and 2D 1H and 13C NMR spectroscopy. The polysaccharide was shown to consist of d-galactose, l-galactose, 2-O-methyl- l-galactose, -O-methyl- l-galactose, 6-O-methyl- d-galactose, d-xylose, and sulfate in a molar ratio of 29:20:5:2:1:20:23. Its agaran-like backbone built up of alternating 3-linked β- d-galactopyranose and 4-linked α- l-galactopyranose residues bears single β- d-xylopyranosyl substituents at position 6 of β- d-galactose residues, whereas sulfate and O-methyl groups occupy positions 2 and 3 of α- l-galactose and position 6 of β- d-galactose residues. A polysaccharide from Corallina pilulifera consisting of d-Gal, l-Gal, 2-O-Me- l-Gal, 6-O-Me- d-Gal, d-Xyl, and sulfate in a molar ration of 29:20:5:2:1:20:23 was shown to contain an agaran-like backbone of alternating 3-linked β- d-Gal p and 4-linked α- l-Gal p bearing single β- d-Xyl p substitutents at O-6 of β- d-Gal p and sulfate mainly at position 2 of α- l-Gal p and 6 of β- d-Gal p residues.