Novel antioxidative and hypoglycemic collagen peptides from Apostichopus japonicus: in silico preparation, functional mechanism, and structure–activity relationship study

The sea cucumber collagen contains a high content of hydrophobic amino acids, which play essential roles in various bioactivities. A total of 2647 unknown active peptide fragments (2–20 amino acids) were obtained via virtual enzymolysis from 16 known collagen sequences in Apostichopus japonicus . Then, the novel bifunctional hexapeptide (DCDPRL, 717.788 Da) with hypoglycemic and antioxidant activities was identified via molecular docking and pharmacokinetics. DCDPRL revealed strong radical scavenging capacity in vitro with IC 50 values for DPPH, ABTS, OH, and O 2 − of 206.12 μM, 186.06 μM, 1.52 mM, and 247.71 μM, respectively. In addition, DCDPRL (250 μM) effectively reduced blood glucose levels and oxidative damage in zebrafish larvae through glucagon-like peptide-1 receptor (GLP-1R), glucose-dependent insulinotropic peptide receptor (GIPR) and Kelch-like ECH-associated protein 1 (Keap1) targets. Furthermore, the structure–activity relationship analysis revealed that sulfur-containing cysteine, hydrophobic amino acids (proline and leucine), and repeated acidic aspartic acid were essential for bifunctional activities.