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

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, 3-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 beta-D-galactopyranose and 4-linked alpha-L-galactopyranose residues bears single beta-D-xylopyranosyl substituents at position 6 of beta-D-galactose residues, whereas sulfate and O-methyl groups occupy positions 2 and 3 of alpha-L-galactose and position 6 of beta-D-galactose residues.