Structural characterization and antioxidant activity of water-soluble polysaccharides from the Tunisian brown seaweed Cystoseira compressa

International audienceA fucoidan (CCF) and a sodium alginate (CCSA) were extracted and purified from the Tunisian brown seaweed Cystoseira compressa. CCF was a highly sulfated heterogalactofucan composed of α-(1→3), α-(1→4)-linked L-Fucp as main backbone which could be highly branched (31.84%) at O-3 and O-4 positions of α-(1→4)-L-Fucp and α-(1→3)-L-Fucp by terminal monosaccharides and side chains such as terminal α-L-Fucp, terminal β-D-Galp, β-D-Galp-(1→3)-α-L-Fucp and β-D-Galp-(1→4)-α-L-Fucp. The ratio of α-(1→3)/α-(1→4) linkages was estimated at 3.86:1. CCSA was characterized by HPAEC-PAD, GC/MS-EI, ATR-FTIR, and 1H-NMR. The M/G ratio was M/G = 0.77, indicating that CCSA respectively contained 44% and 56% of mannuronic and guluronic acids. The values of FGG, FMM, FGM (or FMG) blocks as well as the parameter η were estimated. The two polysaccharides exhibited effective antioxidant activities by ferrous ion chelation, ferric ion reduction and DPPH radical-scavenging, outlining their potentials as natural additives