The Chemical Structure of Gracilaria crassissima (P. et H. Crouan in Schramm et Mazé) P. et H. Crouan in Schramm et Mazé and G. tikvahiae McLachlan (Gigartinales, Rhodophyta) Cell-Wall Polysaccharides
The Chemical Structure of Gracilaria crassissima (P. et H. Crouan in Schramm et Mazé) P. et H. Crouan in Schramm et Mazé and G. tikvahiae McLachlan (Gigartinales, Rhodophyta) Cell-Wall Polysaccharides
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DOI:
10.1515/botm.1988.31.6.491
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发表时间:
1988
期刊:
影响因子:
--
通讯作者:
M. Lahaye;J. Revol;C. Rochas;J. McLachlan;W. Yaphe
中科院分区:
文献类型:
--
作者:
M. Lahaye;J. Revol;C. Rochas;J. McLachlan;W. Yaphe
The matricial and part of the fibrillar polysaccharides from the cell walls of Gracilaria crassissima and G. tikvahiae were investigated using a sequential solvent extraction, C, H nuclear magnetic resonance and infrared spectroscopy, anion exchange fractionation, and X-ray diffractometry. The gel strength of agar fractions from (7. crassissima were also measured. Agar from G. crassissima, composed essentially of agarobiose repeating units with its biological precursor, was extracted with cold water and boiling 60% ethanol. The content of 6-O-methylated agarobiose repeating units in this agar was low, and the substituted disaccharide was principally concentrated in one highly methylated fraction extracted from the alga with boiling 80% ethanol. Alkali treatment of fractions converted the mainly charged molecules to neutral agarose that eluted essentially with distilled water from the anionexchanger. The gel strength, 3,6-anhydrogalactose and sulfate contents of alkali-treated fractions were comparable or better than commercial agar or agarose. Thus, G. crassissima represents an excellent potential commercial resource for agar and agarose. In contrast, with G. tikvahiae the 6-0-methylated agar-containing 4-O-methyl L-galactode, was the principal extract in water at 121 °C, probably reflecting cross-linkages of cell-wall polymers. Alkali treatment of this fraction did not affect its ehition pattern through DEAE-Sephadex, demonstrating that the charge on this agar was not associated with biological precursor repeating units. Analysis of the C NMR spectra of the polymers revealed resonances that were assigned to the 4-O-methyl α-L-galactopyranosc present in this agar. Anion exchange chromatography of agar fractions from these two algae and the different gel strengths obtained between alkali-treated fractions from G. crassissima indicated that the extracts obtained by the 1 Presented in part at the Third European Carbohydrate Symposium, Grenoble, France, September 1985. 2 Present address: INRA-LBTG, BP 527, 44026 Nantes CEDEX 03 3 Deceased, May 1986. Botanica Marina / Vol. 31 / 1988 / Fasc. 6 Copyright © 1988 Walter de Gruyler · Berlin · New York 492 Lahaye et al.: The chemical structure of Gracilaria crassissima and G. tikvahiae cell-wall polysaccharides sequential solvent method were heterogeneous. A combination of sequential solvent extraction of agar and anion exchange chromatography is proposed for obtaining better chemically defined agaroses. Finally, X-ray diffractometry definitively demonstrated the presence of cellulose in the fibrous material recovered after extraction of agar from these two algae.