Alginate fractions from Sargassum vulgare brown seaweed were characterized by (1)H NMR and fluorescence spectroscopy and by rheological measurements. The alginate extraction conditions were investigated. In order to carry out the structural and physicochemical characterization, samples extracted for 1 and 5h at 60 degrees C were further purified by re-precipitation with ethanol and denoted as SVLV (S. vulgare low viscosity) and SVHV (S. vulgare high viscosity), respectively. The M/G ratio values for SVLV and SVHV were 1.56 and 1.27, respectively, higher than the ratio for most Sargassum spp. alginates (0.19-0.82). The homopolymeric blocks F(GG) and F(MM) of these fractions characterized by (1)H NMR spectroscopy were 0.43 and 0.55 for SVHV and 0.36 and 0.58 for SVLV samples, respectively, these values typically being within 0.28-0.77 and 0.07-0.41, respectively. Therefore, the alginate samples from S. vulgare are much richer in mannuronic block structures than those from other Sargassum species. Values of M(w) for alginate samples were also calculated using intrinsic viscosity data. The M(w) value for SVLV (1.94 x 10(5)g/mol) was lower than that for SVHV (3.3 x 10(5)g/mol). Newtonian behavior was observed for a solution concentration as high as 0.7% for SVLV, while for SVHV the solutions behaved as a Newtonian fluid up to 0.5%. The optimal conditions for obtaining the alginates from S. vulgare were 60 degrees C and 5h extraction. Under these conditions, a more viscous alginate in higher yield was extracted from the seaweed biomass.

Previous studies had demonstrated that alginates from Sargassum sp. (Phaeophyta) showed a considerable activity against various murine tumors. The aim present study is to investigate the in vivo antitumor activity of two alginates (SVHV and SVLV) with diVerent viscosity extracted from brown seaweed Sargassum vulgare C. Agardh against Sarcoma 180 cells transplanted in mice. Both alginates inhibited growth of sarcoma 180. The oral route of administration was more eVective for both alginates, leading to an inhibition of 51.8 and 74.8% for SVLV at the doses of 50 and 100 mg/m 2 /day, respectively, and of 66.2 and 88.8% for SVHV at the same doses. SVLV was 2.04 times more active after oral administration, while SVHV was 1.89, both at the dose of 100 mg/m 2 /day. Alginates-antitumor activity was related to the tumor proliferation rate inhibition, as observed by reduction of Ki67 staining in tumor of the treated-animals. The histopathological analysis of liver and kidney showed that both organs were aVected by SVHV and SVLV treatment. However, only SVLV led to acute tubular necrosis. Alginates cause the enlargement of the white pulp of the spleen of treated animals, suggesting that the observed antitumor activity could be related to alginates immunomodulatory properties.