Açaí-derived low-molecular-weight sulfated xylan: structural optimization and anticoagulant/antithrombotic activity

Abstract Hemostasis depends on a tightly regulated balance between procoagulant and anticoagulant mechanisms, and disruption of this equilibrium may result in thromboembolic events. Sulfated polysaccharides from non-animal sources have attracted interest as potential anticoagulant scaffolds; however, low-molecular-weight linear sulfated xylans remain insufficiently characterized regarding their anticoagulant mechanism, antithrombotic efficacy, and parenteral tolerability. In this study, a low-molecular-weight sulfated xylan derivative obtained from Euterpe oleracea pulp, designated NXSo, was prepared by partial acid hydrolysis of native xylan using 1.0 mol L⁻¹ HCl at 100°C for 90 min, followed by SO₃-Py-mediated chemical sulfation in DMF at a 6:1 SO₃-Py:OH molar ratio for 4 h at 50°C. Its anticoagulant activity was evaluated by clotting assays and chromogenic residual activity assays against factor IIa and factor Xa in the presence or absence of antithrombin and heparin cofactor II. NXSo inhibited FIIa activity in an AT-dependent manner, reaching 63% residual activity at 1 µg mL⁻¹, and produced approximately 35% FIIa residual activity via HCII in a dose-independent manner. In vitro , NXSo prolonged aPTT, PT, and TT in a concentration-dependent manner, increasing aPTT up to approximately 2.9-fold at 5 µg mL⁻¹, PT up to approximately 6.3-fold at 80 µg mL⁻¹, and TT up to approximately 3.3-fold at 12 µg mL⁻¹, compared with basal clotting times of 41.9 ± 1.6 s, 13.7 ± 0.4 s, and 14.3 ± 1.4 s for aPTT, PT, and TT, respectively. After subcutaneous administration, NXSo prolonged ex vivo aPTT for up to 12 h, whereas intravenous administration reduced thrombus formation by more than 90% in a stasis- and thromboplastin-induced venous thrombosis model. Docking simulations using a simplified persulfated xylan pentasaccharide model suggested plausible interactions with glycosaminoglycan-recognition regions in antithrombin-containing complexes. However, repeated subcutaneous administration induced localized inflammatory nodules with histological evidence of panniculitis, necrosis, and hemorrhage. Overall, NXSo represents a promising non-animal sulfated polysaccharide scaffold with anticoagulant and antithrombotic activity, but further purification, formulation, and local tolerability optimization are required before therapeutic translation.