Evaluation of the Structure of the Polysaccharides from Chondria macrocarpa and Ceramium rubrum as Determined by 13C NMR Spectroscopy

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Abstract
The polysaccharides from Chondria macrocarpa and Ceramium rubrum were examined by 13C NMR spectroscopy and their spectra were analysed bymeans of set theory. The spectra of the polysaccharides from Chondria macrocarpa collected in autumn were in accord with previous chemical analysis but polysaccharides from seaweed collected in spring comprise a higher level of agar precursors, much lower levels of galactose 2-sulfate, and the polysaccharide is separable into two components, the predominant one of which is essentially free of anhydrogalactose. The signal subset due to the xylosyl unit substituted at the 3-position of 4-linked l-galactose could be assigned from the spectrum of desulfated polysaccharide from Chondria macrocarpa. The extract from Ceramium rubrum consisted of a backbone of 3-linked d-galactosyl units alternating with the 4-linked units 3, 6- anhydro-l-galactosyl and l-galactosyl in a ratio of 2:1 respectively, to which substitution by xylose occurred at approximately 8% of the total sugar units. The natural polymer had moderate levels of sulfate ester, with galactose-6-sulfate being the predominant unit, some of which survives alkaline treatment and was consistent with being 3-linked. There is also evidence of low levels of 3-linked galactose-2-sulfate.