CONCURRENCE OF AGAROID AND CARRAGEENAN CHAINS IN FUNORAN FROM THE REDSEAWEED GLOIOPELTIS-FURCATA POST ET RUPRECHT (CRYPTONEMIALES, RHODOPHYTA)

Funoran extracted from the red seaweed Gloiopeltis furcata Post. et Ru precht was fractionated into four polysaccharide fractions in terms of differences in solubility of their cetylpyridinium salt in potassium chloride solution. Besides the main fraction constructed by an agarose sulphate structure with negative optical rotation, minor polysacchari de fractions with positive optical rotation were obtained. One of the minor polysaccharide fractions contained D- and L-galactose (Gal), 6-O -methyl-D-Gal, 3,6-anhydro-L-Gal and sulphate. Partial hydrolysis and partial methanolysis studies of this fraction led to identification of oligosaccharides attributable to both agaroid and carrageenan backbon es, i.e. [ --> 3)D-Gal(1 --> 4)L-Gal(1 --> ], [ --> 3)D-Gal(1 --> 4)3, 6-anhydro-L-Gal(1 --> ], [ --> 3)D-Gal(1 --> 4)D-Gal(1 --> ] and [ --> 3)6-O-methyl-D-Gal(1 --> 4)D-Gal(1 --> ]. Methylation analysis and al kaline treatment study of this fraction revealed that the sulphate gro ups were located at O-6 of all the (1 --> 4)-linked L- and a part of t he (1 --> 4)-linked D-Gal residues, O-6 of a part of the (1 --> 3)-lin ked D-Gal residue, and both O-2 and O-3 of the (1 --> 3)-linked 6-O-me thyl-D-Gal residue and the other (1 --> 3)-linked D-Gal residue. (C) 1 998 Elsevier Science Limited. All rights reserved.