Polysaccharides from the red seaweed Bostrychia montagnei: chemical characterization
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Bostrychia montagnei was submitted to aqueous extraction at 25 and 85 °C. The purified polysaccharide extracts represent ∼ 17% of the dried alga. Galactose is the principal monosaccharide component of these extracts (60.8–70.4 mol%). 3,6-Anhydrogalactose and its 2- O-methyl derivative are also present in smaller amounts (16.2–22.0 mol%), as well as other methylated sugars, such as 6- O- (6.5–7.8 mol%) and 2-O-methylgalactose (0.2–2.1 mol%). Xylose (4.1–8.1 mol%) and glucose (0.7–2.6 mol%) were also detected. The aqueous extracted polysaccharides (25 °C) were separated by anion-exchange chromatography into six sulphated galactan fractions with negative specific rotations and another two with high xylose contents and positive specific rotations. The sulphated galactans all have an agar type backbone modified by partial O-methyl substitution on O-6 or O-2 of the galactosyl units. The latter substitution is also present in varying degrees of 3,6-anhydrogalactose.
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