Laminarin sulfate from Lessonia flavicans as a potential non-animal anticoagulant with minimal hemorrhagic risk: Structural characterization by NMR spectroscopy and activity analysis

Chemical sulfation of well-defined, low-molecular-weight, non-animal polysaccharides represents a potential approach to anticoagulants that potently inhibit the intrinsic tenase complex (iFXase) while causing fewer side effects, notably a low risk of bleeding. From Lessonia flavicans, we isolated a 5.5-kDa laminarin (LFP0) with a (1 → 3)-β-D-glucan core and trace branching. LFP0 was sulfated under anhydrous and short-time conditions to afford four derivatives (LFP0-S1–S4) with degrees of substitution (DS, 0.1–1.5), molecular weights (6.2–10.9 kDa), and sulfate contents (5.8%–46.2%). Physicochemical analysis and 2D NMR confirmed an intact structure with predominant C-6-O-sulfation, then C-2/C-4 sulfation. The sulfated laminarins prolonged APTT in proportion to DS and left PT unaltered. LFP0-S4, with high FIXa affinity, surpassed LMWH in iFXase inhibition by 80.6% but showed only 58.7% of its TT prolongation, indicating higher selectivity for intrinsic-pathway inhibition. In mice, LFP0-S4 exhibited potent antithrombotic activity without obvious bleeding risk, and showed no toxicity at doses up to 2000 mg/kg. These findings position L. flavicans laminarin as a promising structural blueprint for developing intrinsically targeted anticoagulants and warrant further investigation of its pharmacological and toxicological profiles.