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 by F lavourzyme hydrolysis for 1 h. Both hydrolysates were fractionated using size exclusion chromatography on S ephadex G ‐25 column and purified by RP ‐ HPLC . The amino acid sequence of the most potent and purified fractions was determined using LC / MS / MS . The antioxidant peptide ( KAFAVIDQDKSGFIEEDELKLFLQNFSAGARAGDSDGDGKIGVDEFAALVK , MW : 6334.49 KDa) and NO ‐inhibitory peptide ( AFAVIDQDKSGFIEEDELKLFLQNFSAGARAGDSDGDGKIGVDEFAALVK , MW : 6309.49 Da) produced no cytotoxicity in RAW 264.7 macrophage cell lines at the concentration of 100 mg mL −1 . The purified peptides at the concentration 100 μg mL −1 possessed antioxidative and NO ‐inhibitory activities 83.0 ± 1.1% and 40.9 ± 0.2%, respectively, which were about 100 times those of their counterpart crude hydrolysates.