The structure of the agaran sulfate from Acanthophora spicifera (Rhodomelaceae, Ceramiales) and its antiviral activity. Relation between structure and antiviral activity in agarans Original Research Article

The sulfated agaran isolated by water extraction from the red seaweed, Acanthophora spicifera (Rhodomelaceae, Ceramiales), is made up of A-units highly substituted with sulfate groups on C-2 (28–30%), sulfates on C-2 and 4,6-O-(1′-carboxyethylidene) groups (9–15%), and only the C-2 sulfate groups (5–8%) with small amounts of C-6 sulfate, 6-O-methyl, and nonsubstituted residues. B-units are formed mainly by 3,6-anhydro-α-l-galactose (15–16%) and its precursor, α-l-galactose 6-sulfate (10–17%), together with lesser amounts of 3,6-anhydro-α-l-galactose 2-sulfate, α-l-galactose 2,6-disulfate, α-l-galactose 2,3,6-tri-sulfate, α-l-galactose 2,6-disulfate 3-xylose, 2-O-methyl-α-l-galactose, and unsubstituted α-l-galactose. Small, but significant quantities of β-d-xylose were found in all the fractions, together with small amounts to traces of d-glucose. Some of the fractions have high antiviral activity. Attempts to correlate structure and antiviral activity in agarans are presented.