An Agaroid-Carrageenan Hybrid Type Backbone Structure for the Antithrombotic Sulfated Polysaccharide from Grateloupia indica Boergensen (Halymeniales, Rhodophyta)

The water-soluble antithrombotic polysaccharide sulfate fraction designated GI-1 was isolated from the marine red alga Grateloupia indica . It consists mainly of D-galactose (Gal), L-Gal, 3,6-anhydro-D-galactose (D-AnGal) and 3,6-anhydro L-galactose (L-AnGal). On the basis of the results from 13 C NMR and methylation analysis of completely desulfated GI-1, we assigned a typical agarocolloid-carrageenan hybrid type of the backbone consisting of both disaccharide repeating units, [→3)β-D-Gal(1→4)α-D-Gal(1→] and [→3)β-D-Gal(1→4)α-LGal( 1→]. In addition, two repeating units, [→3)β-D-Gal(1→4)α-D-AnGal(1→] and [→3)β-D-Gal(1→4)α-L-AnGal(1→], were also suggested for the native GI-1 from partial methanolysis and 13 C NMR studies.