Polysaccharides from Enteromorpha compressa: Isolation, purification and structural features

Polysaccharides containing fractions were obtained from the seaweed Enteromorpha compressa by sequential extractions with various solvents. Anion exchange chromatography (AEC) of the oxalate extracted fraction (OSP) yielded rhamnoxylogalactoglucuronan, xyloglucan and glucuronan rich sub-fractions. The heteroglycuronan, which is sulfated, has an apparent molecular mass of 50 ± 20 kDa and is soluble in water. Methylation analysis of the native, desulfated and desulfated reduced heteroglycuronan sulfate suggested that this polymer is branched and contains, inter alia, (1 → 4)- and (1 →  2,4)-linked-rhamnopyranosyl, (1 → 4)-linked xylopyranosyl, and (1 → 4)- and terminally linked glucuronosyl residues. Sulfate groups, when present, are located at C-3 of (1 → 4)-linked rhamnose units and C-2 of (1 → 4)-linked xylose units. Degradation of the xyloglucan rich extract (Ec1OH) by endo-(1 → 4)-β-d-glucanase and analysis of the resulting fragments by matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) showed that the E. compressa xyloglucan contains Glc3Xyl1, Glc4, Glc3Xyl2(SO3Na)2, Glc4Xyl2(SO3Na)2 and Glc5Xyl2(SO3Na)2 as major oligomeric building sub-units.