Cell-wall polysaccharides from the marine green alga Ulva ''rigida'' (Ulvales, Chlorophyta) - NMR analysis of ulvan oligosaccharides

In order to obtain information on sugar sequences in the water soluble polysaccharides from Ulva ''rigida'', oligosaccharides were purified by anion exchange and gel permeation chromatography from the partial acid hydrolysate of the native or desulfated ulvan. The chemical structure acid sugar sequence of these oligomers were determined by H-1 acid C-13 NMR spectroscopy to be alpha-L-rhamnosyl (1 --> 4) D-xylose, beta-D-glucuronosyluronic acid (1 --> 2)-alpha-L-rhamnosyl (1 --> 4) D-xylose, beta-D-glucuronosyluronic acid (1 --> 4) L-rhamnose 3 sulfate, beta-D-glucuronosyluronic acid (1 --> 4) [beta-D-glucuronosyluronic acid (1 --> 2)] L-rhamnose and beta-D-glucuronosyluronic acid (1 --> 4) [beta-D-glucuronosyluronic acid (1 --> 2)] alpha-L-rhamnosyl (1 --> 4) D-xylose. The sugar linkages and particularly the branching and the sulfate position were in total agreement with previous chemical results.