A MODIFIED SYSTEM OF NOMENCLATURE FOR RED ALGAL GALACTANS

A nomenclature system for red algal galactans based on their chemical structures is proposed. The terms 'agaran' and 'carrageenan' are suggested as the generic names for two possible diastereoisometric extreme structures of carbohydrate backbone built of alternating 3-linked beta-D-galactopyranose and 4-linked alpha-galactopyranose residues and differing only in the absolute configuration of the 4-linked alpha-galactose residues (L- or D-, respectively). 'Agarose' and 'carrageenose' are the generic names for the corresponding backbones having 3,6-anhydro-alpha-galactopyranose (also L- and D-) as the 4-linked residue. All the other known regular structures may then be designated as substituted (methylated, sulfated, etc.) derivatives of agaran and agarose (agar group polysaccharides) or carrageenan and carrageenose (carrageenan group polysaccharides). A shortland notation system (uppercase letter code) is also proposed, which is especially useful for designation of hybrid (masked repeating) polysaccharide structures or their corresponding oligosaccharidic fragments and for interpretation of the NMR spectra.