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In the present study, a fucoidan fraction (ANP-3) was isolated from Ascophyllum nodosum , and the combined application of desulfation, methylation, HPGPC, HPLC-MSn, FT-IR, GC–MS, NMR, and Congo red test elucidated ANP-3 (124.5 kDa) as a triple-helical sulfated polysaccharide constituted by →2)-α-Fuc p 3 S -(1→, →3)-α-Fuc p 2 S 4 S -(1→, →3,6)-β-Gal p 4 S -(1→, →3,6)-β-Man p 4 S -(1→, →3,6)-β-Gal p 4 S -(1→，→6)-β-Man p -(1→, →3)-β-Gal p -(1→, α-Fuc p -(1→, and α-GlcA p -(1→ residues. To better understand the relationship between the fucoidan structure of A. nodosum and protective effects against oxidative stress, two fractions ANP-6 and ANP-7 were used as contrast. ANP-6 (63.2 kDa) exhibited no protective effect against H 2 O 2 -induced oxidative stress. However, ANP-3 and ANP-7 with the same molecular weight of 124.5 kDa could protect against oxidative stress by down-regulating reactive oxygen species (ROS) and malondialdehyde (MDA) levels and up-regulating total antioxidant capability (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities. Then metabolites analysis indicated that arginine biosynthesis and phenylalanine, tyrosine, and tryptophan biosynthesis metabolic pathways and metabolic biomarkers such as betaine were involved in the effects of ANP-3 and ANP-7. The better protective effect of ANP-7 compared to that of ANP-3 could be attributed to its relatively higher molecular weight, sulfate substitution and →6)-β-Gal p -(1→ content, and lower uronic acid content. [Display omitted] • The ANP-3 backbone mainly consisted of →3)-α-Fuc p 2 S 4 S -(1→ and →2)-α-Fuc p 3 S -(1→. • ANP-3 and ANP-7 with higher-MWs could reduce oxidative stress while ANP-6 could not. • ANP-3 and ANP-7 inhibited oxidative stress by modulating arginine biosynthesis. • ANP-7 with high sulfate content and molecular weight exhibited a stronger effect. [ABSTRACT FROM AUTHOR]

In the present study, two polysaccharides, SVP2–1 and SVP2–2, were isolated from Patinopecten yessoensis viscera and purified by using DEAE-52 cellulose and Sepharose CL-6B. Both SVP2–1 and SVP2–2 could extend activated partial thromboplastin time (APTT) and thrombin time (TT) and inhibit the transformation of fibrinogen into fibrin (FIB) concentration-dependently, indicating they inhibited clotting and thrombin through intrinsic and common pathways. Of note, SVP2–2 had stronger anticoagulant activity than SVP2–1, and its backbone was determined as →6)-α-Man p (1 → 2)-α-Gal p (1 → with Xyl or Glc substituted at C4 of Gal. Based on monosaccharide composition analysis, methylation analysis, and NMR analysis. Further comparison of their monosaccharide analysis and NMR spectra indicates SVP2–1 and SVP2–2 possess the same core structure features, so the higher sulfate content and lower molecular weight may be the possible reasons for the stronger anticoagulant capability of SVP2–2. The present study suggests acidic polysaccharides from scallop viscera as promising anticoagulant candidates. • Two polysaccharides from scallop viscera were purified and characterized. • They inhibited clotting and thrombin through intrinsic and common pathways. • SVP2–2 with higher sulfate content exhibited stronger anticoagulant effect. • The backbone of SVP2–2 was →6)-α-Man(1 → 2)-α-Gal(1 → with Xyl and Glc at C-4 of Gal. [ABSTRACT FROM AUTHOR]