Isolation, gastrointestinal stability, intestinal transport, and allergenicity of antioxidant peptides derived from crocodile (Crocodylus siamensis) blood proteins.

Antioxidant peptides derived from crocodile blood remain poorly characterized, regarding defined sequences, gastrointestinal stability, intestinal transport, and allergenicity. In this study, antioxidant peptides were generated from crocodile (Crocodylus siamensis) blood proteins via enzymatic hydrolysis. Two peptides (MLHVGPEIAPL and AAHYPKDFGL), prepared by pepsin, exhibited strong antioxidant activity, with 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity of 10.39-14.09 μmol Trolox equivalents (TE)/mg and reducing power of 2.43-5.00 μmol TE/mg. Simulated gastrointestinal digestion revealed that AAHYPKDFGL was further hydrolyzed into shorter peptides (AAHYPK and DFGL) with retained activity. These peptides could pass the Caco-2 monolayer with apparent permeability coefficients of 2.80-11.98 × 10-7 cm/s, despite being degraded by aminopeptidase N to varying degrees. They reduced cellular oxidative stress (decreased superoxide/malondialdehyde levels) without affecting major antioxidant enzymes. No significant allergenicity was detected for these peptides. These findings highlighted crocodile blood proteins as an underexplored source of antioxidant peptides for functional food application.