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The composition, structure and molar mass distribution of Anacardium occidentale exudate polysaccharide of Brazilian origin was investigated. The composition from gas–liquid chromatography (GLC) and 13C NMR was 72% β‐D‐galactopyranose, 14% α‐D‐glucopyranose, 4·6% α‐L‐arabinofuranose, 3·2% α‐L‐rhamnopyranose and 4·5% β‐D‐glucuronic acid. A thorough analysis of high resolution 13C NMR spectra from intact, partially hydrolysed and Smith‐degraded polysaccharide enabled reliable chemical shift assignments to be made, and indicated the presence of three types of unit within the branched galactan core: linked at C‐1 and C‐3, at C‐1 and C‐6, and at C‐1, C‐3 and C‐6. The polysaccharide was fractionated with respect to molar mass using water/ethanol as a solvent/non‐solvent system. The polysaccharide and fractions were characterized by gel permeation chromatography (GPC), intensity light scattering, dilute solution viscometry and sedimentation velocity. The intrinsic viscosity in 0·1M aqueous NaCl at 25°C was found to depend on molar mass according to: [η]/(cm3g‐1)=0·052M0·42. The molar mass distribution for the whole polysaccharide, determined by GPC using a universal calibration, exhibited two main peaks at 28000 and 67000gmol‐1, together with traces of much higher molar mass material. © 1998 SCI.

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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.

The method was appropriate to quantify gutta-percha and resin/wax components of gutta-percha points, but not barium sulphate and zinc oxide. An alternative procedure to determine barium sulphate and zinc oxide contents has been proposed based on elemental microanalysis of sulphur. Some brands of gutta-percha did not contain barium sulphate.

Seaweeds are considered an important source of bioactive molecules. In this work the marine red alga Gracilaria caudata was submitted to aqueous extraction of their polysaccharides for 2 h at 100 °C. The polysaccharide fraction (PGC) presented a recovery of 32.8%. The sulfate content of PGC, calculated by S%, is 1 ± 0.2% and the degree of sulfation accounts for 0.13 ± 0.2. High-Performance Size-Exclusion Chromatography demonstrated that PGC consists of a high molecular weight polysaccharide (2.5 × 10(5)gmol(-1)). Chemical analysis of PGC was performed by microanalysis, infrared (FT-IR) and nuclear magnetic resonance (NMR, 1 and 2D) spectroscopy. The structure of PGC is mainly constituted by the alternating residues 3-linked-β-D-galactopyranose and 4-linked-3,6-α-L-anhydrogalactose; however some hydroxyl groups were substituted by methyl groups and pyruvic acid acetal. The biological precursor of 3,6-α-L-anhydrogalactose (6-sulfate-α-l-galactose) was also detected.

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