Structural characterization of novel polysaccharides from Sargassum fusiforme with dual anticoagulant activity targeting thrombin and antithrombin III.

The polysaccharide from Sargassum fusiforme, an edible brown algae, exhibits anticoagulant activity and benefits cardiovascular health, yet structural studies are limited. Herein, crude polysaccharide from S. fusiforme (CPSF) was extracted and isolated, which demonstrated anticoagulant activity when orally administered. A polysaccharide fractionation map of S. fusiforme was established. Bioassay-guided fractionation yielded homogeneous and bioactive polysaccharides from CPSF. Notably, structurally novel SF4B (6.37 × 106 Da) displayed dual target anticoagulant activity by directly inhibiting thrombin and activating antithrombin III (AT-III). Through integration of structural information from NMR, HILIC-MS/MS, etc., SF4B was deduced as a backbone of →4)-α-Fucp-(1 → with branches at C2 position and occasional sulfations at O-3 position. The branches consisted of β-Galp2S-(1 → or β-Xylp-(1 → 6)-α-Glcp-(1 → 6)-α-Glcp-(1 → 6)-α-Glcp-(1→, which might facilitate the binding of SF4B to AT-III. Moreover, a rapid approach for permethylation validation via crystal water was established. Our study provides structural insights into future potential applications of S. fusiforme anticoagulant polysaccharides in functional food.