Characterization of polysaccharides extracted from brown seaweeds

The structural characteristics of polysaccharides extracted from Quebec's seaweed have not been fully established to date. Ascophyllum nodosum, Fucus vesiculosus and Saccharina longicruris were studied in this research. The seaweeds were treated with selective solvents to extract laminaran and fucoidan in mixture (fraction A), fucoidan (fraction B), and alginate (fraction C). Analyses were performed to determine their content in sulphates, total sugars and uronic acids. H NMR was additionally performed on alginate extract. Results showed that the laminaran extracted from S. longicruris contained 99.1% of the total sugars while the extracts from A. nodosum and F. vesiculosus contained 89.6% and 84.1 %, respectively. The fucoidan found in fractions A and B was shown to have different structures. F vesiculosus and S. longicruris showed important variations in terms of total sugars, uronic acids and molecular weight of polysaccharide. A. nodosum, on the other hand, had a more stable composition, with the exception of the polysaccharide molecular weight. Alginate from S. longicruris had the lowest molecular weight (106.6 kDa) with a F-MM blocks proportion of 0.07 and F-GG blocks of 0.25. Their characterization will lead to a better understanding of their functional characteristics and promote the exploitation of this natural resource. (C) 2007 Elsevier Ltd. All rights reserved.