Carrageenan and agaran structures from the red seaweed Gymnogongrus tenuis

The galactan system biosynthesized by the red seaweed Gymnogongrus tenuis [Phyllophoraceae] is constituted by major amounts of k-l-carrageenans, with predominance of structures, which were isolatedby extraction with hot water in high yield [¡Brought near 45per cent]. A small amount of non-cyclized carrageenans mostlyof the v-type was also obtained. Besides, 12 per cent of these galactans are agaran structures, which were presentin major quantities in the room temperature water extracts, but they were also found in the hot waterextract. They are constituted by 3-linked ß-d-galactose units partially substituted on C-6 with sulfate orsingle stubs of ß-d-xylose and 4-linked residues that comprise -l-galactose units partially sulfated ormethoxylated on C-3 or sulfated on C-3 and C-6 and 3,6-anhydro--l-galactose. Related structural pat-terns were previously found for agarans synthesized by other carrageenophytes. Results presented hereshow that these agarans are low molecular weight molecules independent of the carrageenan structures,with strong interactions between them.