CARRAGEENAN FROM THE TETRASPORIC STAGE OF GIGARTINA-DECIPIENS (GIGARTINACEAE, RHODOPHYTA)

The structure of the polysaccharide isolated from tetrasporophytic pla nts of the New Zealand red alga Gigartina decipiens has been determine d by chemical and spectroscopic techniques. It is a linear polymer com posed primarily of alternating 3-linked beta-D-galactopyranosyl 2-sulp hate and 4-linked alpha-D-galactopyranosyl 2,6-disulphate residues. Ab out 15% of the 3-linked residues have an additional sulphate ester gro up at the 6-position. Aside from this small extra sulphate substitutio n, the structure is that of the idealised lambda-carrageenan. Good qua lity solution-state C-13 NMR spectra were recorded and interpreted for this carrageenan and for the carrageenans produced from it by solvoly tic desulphation and alkali modification.