Chemical composition and super(13)C NMR spectroscopic characterisation of ulvans from Ulva (Ulvales, Chlorophyta)

• Published in: Journal of applied phycology 1999-01, Vol.11 (1), p.1-7
• Main Authors: Lahaye, M, Cimadevilla, EA-C, Kuhlenkamp, R, Quemener, B, Lognone, V, Dion, P
• Format: Article
• Language: English
• Subjects: Brackish; Chlorophyta; Marine; Ulva
• ISSN: 0921-8971
• DOI: 10.1023/A:1008063600071

The chemical composition and structures of several ulvan extracts isolated from various Ulva species were studied. They were all composed mainly of rhamnose, glucuronic acid, xylose, glucose and sulphate with smaller amounts of iduronic acid and traces of galactose. Proteins were also present, most likely as contaminants. Precise quantification of the uronic acid content by chemical-enzymatic hydrolysis coupled to HPAEC-PAD analysis and by colorimetry was not achieved, most likely due to the incomplete hydrolysis of glucuronan segments, inadequate HPAEC-pulsed-amperometric response factor for iduronic acid and to a possible differential colorimetric response of the two uronic acids. super(13)C NMR spectroscopic investigation of different ulvans demonstrated that they were all based on ulvanobiuronic acid 3-sulphate A and B repeating units [ beta -D-GlcpA-(1->4)- alpha -L-Rhap3S and alpha -L-IdopA-(1->4)- alpha -L-Rhap3S, respectively] as well as contiguous beta 1->4 linked D-glucuronic acids possibly occurring either in ulvan or as a separate glucuronan. Marked variations in the content of the repeating structures were seen among the different samples. However, due to the limited number of samples studied, no conclusion was reached concerning the effects of species and ecophysiological conditions on the chemistry of ulvan.