Antioxidative and antihypertensive potential of papain-mediated bull's eye (Priacanthus hamrur) fish skin hydrolysate: Process optimization, structural characterization and cytotoxicity assessment

Abstract

The growing demand for sustainable bioactive compounds has encouraged the valorization of fish-processing by-products into functional ingredients. This study optimized the production of hydrolysate from bull's eye (Priacanthus hamrur) skin and evaluated its antioxidant and antihypertensive activities. Using response surface methodology, optimal conditions were established at enzyme concentration 3%, hydrolysis time 57.06 min, temperature 45°C, and pH 7.50, yielding a hydrolysate with high antioxidant capacity. FTIR spectra displayed characteristic amide I–III bands, confirming peptide bond formation, while XRD patterns indicated an amorphous structure. The fish skin hydrolysate (FSH) showed strong radical-scavenging, reducing, metal-chelating, and lipid-peroxidation-inhibiting activities, which increased proportionally with protein concentration. The hydrolysate also exhibited ACE-inhibitory activity with an IC₅₀ value of 1.60 mg/mL, indicating potential antihypertensive activity. Moreover, the hydrolysate maintained >90% fibroblast cell viability, indicating non-cytotoxicity and biocompatibility. This study demonstrates the novel use of bull's eye skin as a sustainable marine source of multifunctional peptides, supporting the circular bioeconomy and offering promising applications in food, nutraceutical, and pharmaceutical formulations.