Isolation and chemical characterization of algal polysaccharides from the green seaweed Ulva clathrata (Roth) C. Agardh

In order to obtain information on the content and composition of the water-soluble polysaccharides from Ulva clathrata, an extraction at 60°C, in different media, was performed: water, EDTA and HCl (F-I), each followed by a sequential extraction in NaOH 0.1 M (F-II). The extracts were recovered and analyzed for total carbohydrates, proteins, rhamnose, uronic acids and sulfate content. Differences were obtained in the yield and composition in both fractions of the different media (F-I and F-II). Higher yields resulted in the first fraction on all media. HCl extraction was the best in both fractions (14.83 ± 1.5% and 5.96 ± 1.1%, F-I and F-II, respectively). In all cases, F-I was more sulfated ranging from 27.87% to 35.8% and higher in rhamnose content, whereas F-II had higher protein and slightly higher uronic acid content. FTIR spectra showed that soluble polysaccharides from the green seaweed U. clathrata are sulfated polysaccharides, similar to ulvan obtained from other Ulva species and confirmed by the 1 H-NMR spectrum, where the characteristic signal for the deoxy sugar (rhamnose) is present.