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STRUCTURAL STUDIES ON AGAR FRACTIONS EXTRACTED SEQUENTIALLY FROM CHINESE RED SEAWEEDS:GRACILARIA SJEOSTEDTII, G. TEXTORII AND G. SALICORNIA USING~(13)C-NMR AND IR SPECTROSCOPY

纪明侯  M.Lahaye  W.Yaphe  
【摘要】:正 The polysaccharides of three species of Chinese Gracilaria (Rhodophyta) were extracted by sequential solvent extraction and the chemical structures of the fractions obtained were investigated by using 13C-NMR and IR spectroscopy.The 13C-NMR spectra showed that the main extract, cold water fraction, from G. sjeostedtii consisted of repeating disaccharides of agarobiose and (1→3)-β-D-galactopyranosy 1-(1→4)-α-L-galactopyranose 6-sulfate, the latter being a precursor to agarobiose and converted to agarobiose after alkali modification. The component of the 60% ethanol fraction from G. textorii was composed mainly of agarose 6-sulfate, 6-O-methyl-agarose and some amount of agarose, whose structures remained unchanged after alkali treatment. The autoclave extract from G. salicornia revealed a complex structure composed of 6-0-methyl-agarose, 2-0-methyl-agarose, branched 4-0-methyl-L-galactose and agarose 4-sulfate, All the substiluents in these agaroses, were stable against alkali treatment. The alkali ex

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