Chemical composition and 13C NMR spectroscopic characterisation of ulvans from Ulva (Ulvales, Chlorophyta) |
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Authors: | Marc Lahaye Enrique Alvarez-Cabal Cimadevilla Ralph Kuhlenkamp Bernard Quemener Vincent Lognoné Patrick Dion |
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Institution: | (1) INRA, URPOI, BP 76157, 44316 Nantes, France;(2) CEVA, BP 22610, Pleubian, France |
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Abstract: | 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. 13C NMR spectroscopic investigation of different ulvans demonstrated that they were all based on ulvanobiuronic acid 3-sulphate
A and B repeating units β-D-Glc pA-(1->4)-α-L-Rhap3S and α-L-IdopA-(1->4)-α-L-Rha p3S, respectively] as well as contiguous
β 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.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | ulvan Ulva HPAEC-PAD NMR spectroscopy iduronic acid |
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