Author(s): Torres, Marcia R. ; Sousa, Alessandra P. A. ; Silva Filho, Eduardo ; Melo, Dirce F. ; Feitosa, Judith P. A. ; Paula, Regina Célia Monteiro de ; Lima, Maria G. S.
Date: 2013
Origin: Oasisbr
Subject(s): Feófitas; Espectroscopia de Ressonância Magnética
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 5 h at 60 C were further purified by re-precipitation with eth- anol 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. There- fore, 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 · 10 5 g/mol) was lower than that for SVHV (3.3 · 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 C and 5 h extraction. Under these conditions, a more viscous alginate in higher yield was extracted from the seaweed biomass
