STRUCTURAL FEATURES OF THE CELL WALL COMPONENTS FROM CODIUM FRAGILE AND C. VERMILARA (BRYOPSIDALES, CHLOROPHYTA)

MARINA CIANCIA; JOSÉ MANUEL ESTEVEZ; ALBERTO SAÚL CEREZO

Kobe, Japón

Simposio; XIX International Seaweed Symposium; 2007

International Seaweed Asociation

Seaweeds of the genus Codium biosynthesize sulfated arabinogalactans, as major water-soluble polysaccharides, which have important biological activities. Although many papers have been published about them, the structure of these products was not completely established and for different species and even for the same species, discrepancies in the quantities of arabinose and galactose were found, ranging from the pure arabinan to the pure galactan, possibly in part due to different isolation and purification procedures. Both seaweeds were extracted with water at rt. and 90°C and the extracts and residues were analyzed. As expected, arabinogalactans were the major products in the first extracts, which differed in composition and sulfate content. The other extracts were enriched in b-mannans and a-glucans for C. fragile, but important amounts of arabinogalactans and only minor quantities of starch were extracted from C. vermilara and the final residue obtained after water extraction showed only small amounts of glucose. The structure of the major sulfated arabinogalactan was determined for both seaweeds, showing a main a-(1®3)-L-arabinopyranose backbone, substituted on C-4 and partially on C-2 by sulfate and side chains, arabinose was also present in small amounts as terminal unit in the furanose form; while the 3-linked D-galactopyranose units were partially substituted on C-4, C-6, or both positions with sulfate or pyruvylated. These products were extracted as a mixture of polysaccharides and proteoglycans, thus the aminoacid composition was also determined. Significant differences were found between the structures of the polysaccharides from these two species that were analyzed.