Hemostatic Activity of Orally Administered Melanin from Cuttlefish Ink Sacs in a Rat Tail-Bleeding Model

Cuttlefish ink sac is an underutilized marine processing by-product with considerable potential for value-added conversion into functional ingredients. In this study, high-purity cuttlefish melanin (HCM) was isolated from cuttlefish ink sacs, and its hemostatic activity, safety, and intestinal metabolites were investigated to support its functional application. SEM-EDS analysis shows that HCM consisted of black spherical nanoparticles enriched in calcium and magnesium. Multi-technique characterization (UV–Vis, FTIR, XPS, and Raman) confirmed the material as melanin, with characteristic optical absorption, surface functional groups, and elemental composition. In a rat tail-bleeding model, HCM significantly reduced blood-loss volume and shortened bleeding time, indicating promising hemostatic activity in vivo. To explore the underlying mechanism, intestinal metabolites of HCM were characterized by UHPLC-Q-Orbitrap HRMS-based metabolomics. TXA and ACA were detected in the intestinal contents following HCM administration. Additionally, HCM released Ca2+ and Mg2+, which may contribute to regulating coagulation. Consistently, HCM significantly shortened prothrombin time and increased fibrinogen levels, while other coagulation parameters remained within the normal range. These results suggest that HCM may exert hemostatic effects through dual pathways involving fibrinolysis inhibition and coagulation promotion. Overall, this study provides mechanistic insight into the hemostatic activity of cuttlefish melanin and supports the high-value utilization of cuttlefish ink sac by-products as a source of marine-derived functional ingredients.