Abstract

The galactans extracted with hot water from Kappaphycus alvarezii, after previous extraction at room temperature, are mainly composed of kappa-carrageenans (similar to 74%) and mu-carrageenans (similar to 3%). However, a significant percentage of these galactans (at least 14%) is composed of 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 beta-D-galactose units and on C-3 or C-2 and C-3 of the alpha-L-galactose residues with sulfate groups or single stubs of beta-D-xylopyranose, D-glucopyranose, and galactose or with D-glucopyranosyl-(1-->4)D-glucopyranose side chains. Significant quantities of 2-O-methyl- and 3-O-methyl-L-galactose units are also present. A. A great tendency to retain Ca2+ and Mg2+, in spite of 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 interactions. (C) 2004 Elsevier Ltd. All rights reserved.