Isolation and chemical characterization of algal polysaccharides from the green seaweed Ulva clathrata (Roth) C. Agardh Enrique Hernández-Garibay & Jose A. Zertuche-González & Isai Pacheco-Ruíz Received: 26 March 2010 / Revised and accepted: 1 November 2010 # Springer Science+Business Media B.V. 2010 Abstract 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 carbohy- drates, 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. Keywords Green seaweeds . Rhamnose . Sulfated polysaccharides . Ulva clathrata . Uronic acids Introduction Green algae, in particular Ulva species, are distributed worldwide, growing in the intertidal and subtidal zones, attached to hard substrate or as free-living form. They are considered opportunistic seaweeds and proliferate in eutro- phicated coastal waters (Borowitzka 1972; Teichberg et al. 2010). Different Ulva species are used as food in Japan; the mixture of Ulva pertusa, Enteromorpha prolifera and Monostroma latissimum is known as the commercial product “Aonori” or “green laver” (Nisizawa et al. 1987). In Europe, Ulva is used sometimes in poultry nutrition to improve the egg yolk and meat colouration (Indergaard and Minsaas 1991). It is well known that the Ulva species do not have any commercially important hydrocolloid, but they are an important source of complex polysaccharides; these include four polysaccharide families, two major ones, the water- soluble ulvan and insoluble cellulose, and two minor ones, the alkali-soluble linear xyloglucan and a glucuronan (Lahaye and Robic 2007). In particular, ulvan is a water- soluble, sulfated, anionic polysaccharide, mainly made of rhamnose, sulfate groups and uronic acids (Percival and McDowell 1967; Medcalf et al. 1972; Robic et al. 2009a, b, c), occurring mainly as aldobiuronic acid, 4-Ο-β-D- glucoronosyl-α-L-rhamnose or as ulvanobioses, where E. Hernández-Garibay (*) Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Carretera Tijuana-Ensenada km. 107, 22860, Ensenada, Baja California, Mexico e-mail: garibay58@yahoo.com E. Hernández-Garibay : J. A. Zertuche-González : I. Pacheco-Ruíz Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Carretera Tijuana-Ensenada km. 107, 22860, Ensenada, Baja California, Mexico E. Hernández-Garibay Centro Regional de Investigación Pesquera de Ensenada, Instituto Nacional de Pesca y Acuacultura, Carretera Tijuana-Ensenada km. 97.5, 22800, Ensenada, Baja California, Mexico J Appl Phycol DOI 10.1007/s10811-010-9629-0