Agaroids from New Zealand members of the Gracilariaceae (Gracilariales, Rhodophyta) — a novel dimethylated agar

✍ Scribed by Richard H. Furneaux; Ian J. Miller; Thomas T. Stevenson

• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 682 KB
• Volume: 204-205
• Category: Article
• ISSN: 1573-5141
• DOI: 10.1007/bf00040300

✦ Synopsis

Polysaccharide extracts from four New Zealand members of the Gracilariaceae have been characterized by 13 C-NMR spectroscopy and GLC analysis of alditol acetate derivatives prepared using a new double hydrolysis-reduction procedure . All were based on variously substituted repeating disaccharide units of agarobiose and _< 20 % of its `precursor' containing L-galactose-6-sulfate . Gracilaria truncata yielded a firm gelling agar with 67 % methylation on the 6-position of the D-galactose residues . The other extracts belong to a new class of agar molecules having methylation on both the 6-position of the D-galactose units and the 2-position of the L-sugar units . The Curdiea coriacea polysaccharide displayed this double methylation almost completely (>_ 96 %) ; the alkali-modified polymer thus had only two free hydroxygroups per disaccharide repeat unit, yet still gave a firm gel . The Curdiea flabellata and Melanthalia abscissa extracts had this double methylation pattern but to a lesser extent, and additional xylosyl branch units on up to 18 % of the repeating disaccharide units .