Abstract:
The wastewater produced during the commercial processing of pre-salted jellyfish (Lobonema smithii) from ponds was rich in many short-chain peptides. These peptides are produced during autolysis process of the jellyfish after harvesting them from seawater. This research aimed to analyse bioactive short-chain peptides from wastewater in pre-salted jellyfish (Lobonema smithii) processing with a focus on antioxidant activity. The results showed that the antioxidant peptide fractions from the wastewater were purified by cation exchange and reversed phase chromatography, respectively. Then, the amino acid sequences of the peptides obtained were then identified by the LC-MS/MS technique. The six candidate peptides which might contain antioxidant activity were identified (CVICRSIYDRNEIG (P1), NLVDLAEKAQLLHE (P2), ARIKFNSKLKPMLYIM (P3), KNIQYKVVKKK (P4), KEKNPPYLRFLTVL (P5) and RYRLRKKFPFPPT (P6)). The six peptides were synthesized and their antioxidant activity was evaluated using the standard Trolox at a concentration of 0.1 mg/mL according to DPPH, ABTS and FRAP methods. The experiment revealed that the ABTS method could identify the antioxidant activity of each peptide sequence. Except for NLVDLAEKAQLLHE (P2), the antioxidant activity concentration of 10 percent (IC10) as determined by the ABTS technique was in the range of 0.23 to 1.34 mg/mL. After testing the stability of all six sequences of peptides, KNIQYKVVKKK (P4) and KEKNPPYLRFLTVL (P5) remained stable over a range of temperatures (30, 50, 70, and 90 °C). While the bioactivity of, ARIKFNSKLKPMLYIM (P3), KNIQYKVVKKK (P4), KEKNPPYLRFLTVL (P5), and RYRLRKKFPFPPT (P6) still remained after exposure to pH (3.6, 5, 7, 8.5). KNIQYKVVKKK (P4) showed high activity after an in vitro gastrointestinal digestion. This research provided novel knowledge not only for future food but also pharmaceutical application.