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Characterization of galactose from carrageenans by natural abundance site‐specific isotope parameters
Author(s) -
Zhang Ben Li,
Vallet Claude,
Blanchard Frédérique,
Martin Gérard J.,
Combaut Georges
Publication year - 1994
Publication title -
phytochemical analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 72
eISSN - 1099-1565
pISSN - 0958-0344
DOI - 10.1002/pca.2800050604
Subject(s) - chemistry , galactose , derivatization , deuterium , fractionation , isotope fractionation , isotope , isotope ratio mass spectrometry , isotope analysis , stable isotope ratio , chromatography , mass spectrometry , organic chemistry , ecology , physics , quantum mechanics , biology
The overall 13 C or 2 H content of the organic matter of marine algae is an interesting source of information on metabolic and environmental effects experienced by aquatic plants. However, in order to appraise the complexity of the phenomena which influence the isotopic distribution, access to more specific isotopic probes is desirable. Thus, determination of the overall and site‐specific natural deuterium fingerprint of the galactose unit of carrageenans is expected to improve the characterization of these molecular species in terms of origin and history of the precursors. A strategy has been developed in order to render the galactose moiety accessible to the study of site‐specific natural isotope fractionation of hydrogen by nuclear magnetic resonance (SNIF‐NMR). Extraction and derivatization procedures have been elaborated and the possible occurrence of fractionation effects in the course of the physical and chemical transformations has been examined. By combining mass spectrometric determination of the overall isotope ratio of the galactose skeleton and analysis of the cluster signals observed in the 2 H‐NMR spectra of appropriate galactose derivatives, several groups of site‐specific isotope contents can be obtained. Significant deviations with respect to a statistical distribution of deuterium in the galactose unit have been determined and the isotopic parameters of galactoses from carrageenans have been shown to differ greatly from those of galactose extracted from milk. Moreover, significant variations are observed among the different sources of carrageenans. This behaviour is consistent with the large range of overall isotope contents measured in cellulose from aquatic plants.