Isolation and characterization of an antitumor active agar-type polysaccharide of Gracilaria dominguensis

Cold water extraction of the red alga Gracilaria dominguensis, followed by cetyltrimethylammonium bromide fractionation, gave a highly sulfated, agar-type polysaccharide which inhibited the transplantation of Ehrlich ascites carcinoma in mice. The structure of the polysaccharide has been investigated by methylation analysis, and 1H- and 13C-n.m.r. spectroscopy, and was shown to be mainly composed of alternating (1→3)-linked β- d-galactopyranosyl 6-sulfate and (1→4)-linked 3,6-anhydro-α- l-galactopyranosyl residues.