The chemical composition and the structure of gametic, carposporic and tetrasporic water-soluble polysaccharides from Asparagopsis armata Harvey (Rhodophyta, Bonnemaisoniaceae), as well as two gametic samples harvested both in the Mediterranean Sea and Atlantic Ocean, have been compared. The structural analysis of the polysaccharides has been examined by infra-red spectroscopy and by methylation of native and desulphated samples. The different constitutive sugars have been separated and quantified by gas-phase chromatography after reductive hydrolysis. The sulphated galactans lacking anhydrogalactose have both carrageenan and agar features such as high proportions of 1,3- and 1,4-linked galactose units, the presence of D- and L-galactose units, and negative or positive optical rotation values according to the stage considered. They are essentially sulphated on C-4 and ramified on C-3 and C-6. The carposporic polysaccharide differs primarily from the others by the presence of 15.9% dry wt uronic acids and a threefold lower sulphation level.
