Antioxidant peptides have elicited interest for the versatility of their use in the food and pharmaceutical industry. In the current study, antioxidant peptides were prepared by microwave-assisted alkaline protease hydrolysis of collagen from sea cucumber (Acaudina molpadioides). The results showed that microwave irradiation significantly improved the degree of hydrolysis of collagen and the hydroxyl radical (OH⋅) scavenging activity of hydrolysate. The content and OH⋅ scavenging activity of collagen peptides with molecular weight ≤ 1 kDa (CPS) in the hydrolysate obtained at 250 W increased significantly compared with the non-microwave-assisted control. CPS could scavenge OH⋅ and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in a dose-dependent manner. The scavenging activity of OH⋅ and DPPH radical was 93.1% and 41.2%, respectively, at CPS concentration of 1 mg/mL. CPS could significantly promote RAW264.7 cell proliferation and reduce the Reactive Oxygen Species (ROS) level of H2O2-induced damage in RAW264.7 cells in a dose-dependent manner. Furthermore, all CPS-treated groups exhibited an increase in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and a decrease in malondialdehyde (MDA) level compared with the control. These results showed that CPS could effectively protect RAW264.7 cells from H2O2-induced damage, implying the potential utilization of CPS as a natural antioxidant for food and pharmaceutical applications.

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Sea cucumbers are traditional marine food in Asian countries. In this work, the chemical elements accumulated in sea cucumber Acaudina leucoprocta from the East China Sea were measured and analyzed. The contents of Zn, Mn, Cu, As, Pb, Cd and Cr increased with the increase of weight of A. leucoprocta. The levels of Pb and As in all the examined individuals were higher than the maximum residue limits (MRLs) permitted in foodstuffs. The metals were found to be selectively distributed in the body compartments of A. leucoprocta. The highest contents of heavy metals As, Pb were found in intestines and body wall, while the lowest in anus and internal organ. An efficient chemoenzymic method by combining proteolytic enzymatic hydrolysis with citric acid soaking was established to remove the heavy metals in sea cucumber A. leucoprocta. The concentrations of both As and Pb were decreased to below 0.5 mg kg _ 1 in all the samples.