Effect of Crassostrea hongkongensis polysaccharide fraction enriched in ≤ 3 kDa molecules on antithrombotic activity in black-tailed mice

Oyster, a dominant bivalve in coastal China, is a valuable source of bioactive marine polysaccharides. Furthermore, low-molecular-weight polysaccharides exhibit superior biological activity and bioavailability compared to ultra-high-molecular-weight polysaccharides. This study aims to extract antithrombotic polysaccharides from Crassostrea hongkongensis meat and investigate their in vivo antithrombotic activity through mouse experiments. Oyster polysaccharides (OP) were obtained through enzymatic hydrolysis and Sevag method for protein removal. Oyster polysaccharide fraction enriched in ≤3 kDa molecules (POP) was derived via degradation with saccharifying enzymes, cellulase, α-amylase, and dialysis. Chemical composition was analyzed, and structure was characterized using UV–Vis, FTIR, Congo red (CR) staining and ¹H and ¹³C NMR spectroscopy. A mouse blacktail thrombosis model was established to assess in vivo coagulation function. Results showed that compared to OP, POP exhibited increased total sugar (71.75%), polysaccharides (67.90%), and sulfate group (8.44%) contents, while protein content decreased to 9.80% (p < 0.01). Structural analysis revealed both compounds possess typical polysaccharides functional groups, with POP exhibiting a more stable triple-helical conformation. In animal experiments, the high-dose POP group (200 mg/kg) achieved a thrombosis inhibition rate of 56.41% and a clotting time prolongation rate of 65.32%, with no significant differences in either metric compared to the clopidogrel positive drug group (p > 0.05). These results indicate that the OP and POP isolated in this study exhibit antithrombotic and anticoagulant activities, providing theoretical support for the development of antithrombotic health foods or pharmaceuticals.