The system of galactans biosynthetized by Kappaphycus alvarezii with emphasis on its minor components.

ESTEVEZ, J. M.; CIANCIA M. & A. S. CEREZO.

Trondheim, Noruega

Simposio; XVIII International Seaweed Symposium; 2004

 The galactans extracted with hot water from Kappaphycus alvarezii, after previous extraction at room-temperature, are mainly composed by kappa-carrageenans (» 74 %) and mu-carrageenans (» 3 %). However, a significant percentage of these galactans (at least 14 %) is composed by sulfated agarans and, possibly, agaran-type sulfated dl-hybrid galactans. These agarans are partially substituted on C-2 or C-4 or disubstituted on both positions of the b-d-galactose units and on C-3 or C-2 and C-3 of the a-l-galactose residues with sulfate groups or single stubs of b-d-xylopyranose, d-glucopyranose and galactose or with 4-O-(d-glucopyranosyl)-d-glucopyranose side chains. Significant quantities of 2-O-methyl- and 3-O-methyl-l-galactose units are also present. A great tendency to retain Ca2+ and Mg2+, in spite of the massive treatments with Na+ and K+ salts was observed. The complexation between agarans and agarans-kappa-carrageenans through divalent cations and the possible zipper-type carbohydrate-carbohydrate interactions would be two complementary mechanisms of interaction.     Keywords.- carrageenans; agarans; sulfated galactans; structure determination; Kappaphycus alvarezii; red seaweed; Ca2+-polysaccharide interactions.