The sea cucumber (Stichopus vastus) is an underutilized species, as most of its parts, including the integument (high collagen content) are thrown away during processing. The aim of this study was to investigate the effects of different hydrolysis conditions (substrate to enzyme ratio (S/E), reaction temperature, and hydrolysis time) on the angiotensin I converting enzyme (ACE) inhibitory and radical scavenging (RSc) activities of the hydrolysates produced from trypsin hydrolysis of S. vastus collagen. Optimal conditions predicted by Box-Behnken Design modelling for producing ACE inhibitory and RSc hydrolysates were found to be S/E ratio (15), reaction temperature (55°C), and hydrolysis time (1 h). Under optimal conditions, ACE inhibitory and RSc activities were estimated to be as high as 67.8% and 77.9%, respectively. Besides, some novel bioactive peptides were identified through mass spectrometry analysis. These results indicate that S. vastus hydrolysates might be used as a functional ingredient in food and nutraceutical products.
Collagen isolated from the ribbon jellyfish (Chrysaora sp.) was hydrolysed using three different proteases (i.e. trypsin, alcalase and Protamex) to obtain bioactive peptides. Angiotensin-I-converting enzyme (ACE) inhibitory activity and antioxidant activities (i.e. ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity) of the peptides were measured and compared, and the effect of the duration of hydrolysis on the bioactivity (ACE inhibitory and antioxidant activities) of peptides was also evaluated. FRAP activity was the highest in Protamex-induced (25-27 mM) and trypsin-induced hydrolysates (24-26 mM) at 7 and 9 h, respectively. Conversely, hydrolysates produced by trypsin for 1 and 3 h showed the highest DPPH radical scavenging activities (94 and 92%, respectively). Trypsin-induced hydrolysates (at 3 h) also showed the highest ACE inhibitory activity (89%). The peptide sequences with the highest activities were identified using tandem mass spectrometry, and the results show that the hydrolysates had a high content of hydrophobic amino acids as well as unique amino acid sequences, which likely contribute to their biological activities.
The molecular mass distribution, amino acid composition and radical-scavenging activity of collagen hydrolysates prepared from collagen isolated from the sea cucumber Stichopus vastus were investigated. β and α1 chains of the collagen were successfully hydrolysed by trypsin. The molecular mass distribution of the hydrolysates ranged from 5 to 25 kDa, and they were rich in glycine, alanine, glutamate, proline and hydroxyproline residues. The hydrolysates exhibited excellent radical-scavenging activity. These results indicate that collagen hydrolysates from S. vastus can be used as a functional ingredient in food and nutraceutical products.