Purification and characterisation of antioxidant and nitric oxide inhibitory peptides from T ilapia ( O reochromis niloticus) protein hydrolysate

Summary Nitric oxide (NO)‐inhibitory and antioxidative activities of tilapia hydrolysates were prepared using ultrasound pretreatment at 70 W for 30 and 45 min, respectively, followed byFlavourzyme hydrolysis for 1 h. Both hydrolysates were fractionated using size exclusion chromatography onSephadexG‐25 column and purified byRP‐HPLC. The amino acid sequence of the most potent and purified fractions was determined usingLC/MS/MS. The antioxidant peptide (KAFAVIDQDKSGFIEEDELKLFLQNFSAGARAGDSDGDGKIGVDEFAALVK,MW: 6334.49 KDa) andNO‐inhibitory peptide (AFAVIDQDKSGFIEEDELKLFLQNFSAGARAGDSDGDGKIGVDEFAALVK,MW: 6309.49 Da) produced no cytotoxicity inRAW264.7 macrophage cell lines at the concentration of 100 mg mL−1. The purified peptides at the concentration 100 μg mL−1possessed antioxidative andNO‐inhibitory activities 83.0 ± 1.1% and 40.9 ± 0.2%, respectively, which were about 100 times those of their counterpart crude hydrolysates.