Identification and characterization of two novel antioxidant peptides from silkworm pupae protein hydrolysates

Abstract

Silkworm pupae are a kind of insect resource food that rich of good quality protein. To identify the peptide with high antioxidant activity from silkworm pupae protein hydrolysates, and provide the basis for the application of silkworm pupae protein hydrolysates and antioxidant peptides in functional foods, silkworm pupae proteins were hydrolysed by a dual-enzyme system consisting of acidic protease and neutral protease. The hydrolysates were purified sequentially by ultrafiltration, gel filtration chromatography and high-performance liquid chromatography (HPLC). The ABTS radical scavenging activity was used to evaluate antioxidant activity. Fractions with high activity were further analyzed by liquid chromatography- tandem mass spectrometry (LC–MS/MS). Two peptides, FKGPACA and SVLGTGC with molecular weights of 692.34 and 635.30 Da were obtained. To further determine the major active sites of FKGPACA and SVLGTGC, four peptides, FKGP, ACA, SVLG and TGC were artificially synthesized. ACA and TGC had higher ABTS radical scavenging activities than FKGP and SVLG. The main active sites of FKGPACA and SVLGTGC were possibly located in the ACA and TGC fragments, which are related to Cys, Ala or Thr residues. Both FKGPACA and SVLGTGC proved to good antioxidants even after high-temperature thermal processing for 1 h. After digestion with pepsin, the ABTS radical scavenging activity of FKGPACA was stable, while the ABTS radical scavenging activity of SVLGTGC decreased slightly. After further digestion with pancreatin, the ABTS radical scavenging activities of FKGPACA and SVLGTGC decreased by 10.59% and 43.56%, respectively. After digestion with chymotrypsin, the ABTS radical scavenging activities of FKGPACA and SVLGTGC were stable. The silkworm pupae protein hydrolysates and FKGPACA could be potentially used as natural antioxidants in functional foods.