Isolation, purification and identification of three novel antioxidative peptides from patin (Pangasius sutchi) myofibrillar protein hydrolysates

Myofibrillar protein from patin was hydrolysed using papain, alcalase and flavourzyme with differing degrees of hydrolysis (DH) to obtain antioxidative peptides. The protein solubility and peptide content of the myofibrillar protein hydrolysates (MPHs) were observed. The antioxidant activity of the hydrolysates was evaluated. The results showed that the highest DH (89.17%) of MPH was produced by the 120-min papain treatment. When the DH of MPHs increased, protein solubility and peptide content increased. Papain-MPHs exhibited the highest antioxidant activity. The papain hydrolysate was purified using ion exchange chromatography, gel filtration chromatography and RP-HPLC. The potent fraction (MI 4) obtained from RP-HPLC had DPPH radical scavenging activity that was 2.97 times higher than MPH. Three antioxidative peptide sequences were identified as VPKNYFHDIV, LVMFLDNQHRVIRH, and FVNQPYLLYSVHMK according to HPLC and connected to the electrospray ionization-time-of-flight mass spectrometer (ESI-TOF MS/MS). The FVNQPYLLYSVHMK peptide exhibited the highest antioxidant activity. The presence of hydrophobic amino acids (Leu, Val and Phe), hydrophilic and basic amino acids, (His, Pro and Lys), and aromatic amino acids (Phe and Tyr) in the peptide sequences is believed to contribute to the high antioxidant activity of MPHs. These results suggest that MPHs from patin have potential as a natural antioxidants ingredient in foods.