Structural investigation and immunological activity of a heteropolysaccharide from Sargassum fusiforme

• A new heteropolysaccharide was isolated from Sargassum fusiforme.
• The predicted structure was elucidated by chemical and spectral methods.
• The heteropolysaccharide can reverse the immunosuppression in CTX-treated mice.

A heteropolysaccharide was isolated from the brown alga, Sargassum fusiforme. The heteropolysaccharide was estimated to have a molecular weight of 11 kDa and showed [α]D20 −62.2420 (c 0.05, H2O). SFPS65-B comprised galactose, glucose, mannose, fucose, and galacturonic acid at a ratio of 3.04:1:1.15:2.82:6.51. Its structural features were investigated using composition analysis, methylation analysis, IR, NMR spectroscopy, and ESI-Q-TOF MS spectroscopy. Results showed that SFPS65-B contained the backbone of →4)-α-GalAp-(1→4)-α-Hexp-(1→4)-α-GalAp-(1→4)-α-Fucp-(1→4)-α-GalAp-(1→. The sulfated unit and terminal fucose residues were attached onto the backbone through the O-2 of some galactose residues. Results also showed that SFPS65-B had a good effect on thymus and spleen indices at a dose of 100 mg/kg upon immunosuppression in cyclophosphamide-treated mice.

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