Comparison of Different Preparation Methods for Selenium-Enriched Spirulina Peptides: Structure and in Vitro and in Vivo Bioactivity Assessments.

This study systematically compared the impact of direct (D_SeSPs) and indirect (I_SeSPs) enzymatic hydrolysis on the preparation and bioactivity of selenium-enriched spirulina peptides. Comprehensive evaluation revealed that direct hydrolysis yielded peptides with a higher degree of hydrolysis, selenium content (238.42 μg/g), distinct structural features, including enriched hydrophobic residues and retained selenocysteine motifs, and superior in vitro free radical scavenging capacity. In a H2O2-induced Caco-2 cell model, D_SeSPs demonstrated superior antioxidant activity by activating the Keap1-Nrf2 pathway and enhancing intracellular antioxidant defenses. Furthermore, in a murine model of ulcerative colitis, D_SeSPs alleviated colonic oxidative damage, preserved intestinal barrier integrity, and increased the abundance of beneficial bacteria, including Akkermansia and Blautia. These findings highlight the critical influence of preparation methods on peptide efficacy and identify direct enzymatic hydrolysis as an effective strategy for producing high-performance spirulina-derived selenium supplements for functional food applications.