Structure of agars from Gracilaria tikvahiae rhodophyta: Location of [formula omitted] and sulphate

• Published in: Carbohydrate polymers Vol. 11; no. 4; pp. 265 - 278
• Main Authors: Craigie, J.S., Jurgens, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1989
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/0144-8617(89)90002-7

Agars from young and old tissues of Gracilaria tikvahiae were compared by 13C NMR spectroscopy. An alkali-modified agar containing 4- O-methyl- l-galactose was degraded by β-agarase. Methylation analysis combined with 13C NMR studies established the presence of single 4- O-methyl-α- l-galactopyranosyl -(1 → 6) residues attached as side branches to the 3-linked galactose of the main chain. Repeating units of 6-O-methylagarobiose-4-O-sulphate were detected in agars from old tissues. Enzymolysis with β-agarase released 26·8% of the agar from mature algae, mostly as neoagarobiose, neoagarotetraose and their 6 3-mono-O-methyl and 6 1, 6 3-di-O-methyl derivatives. No 4- O-methyl- l-galactose-containing fragments were detected among the low-molecular-weight products of enzymolysis. The agar from young tissues grown at a suboptimal temperature differs from agars of mature tissues in that it contains low levels of 4-O-sulphate and only traces of 4- O-methyl- l-galactose . It is concluded that physiological condition and growth regimen can induce wide variations in the structure of agar within the same species.