Antioxidant activity of a peptide isolated from Alaska pollack (Theragra chalcogramma) frame protein hydrolysate

Alaska pollack frame protein, which is normally discarded as an industrial by-product in the process of fish plant, was hydrolyzed with mackerel intestine crude enzyme (MICE). Alaska pollack frame protein hydrolysate (APH) was fractionated according to the molecular basis into five major types of APH-I (30-10 kDa), APH-II (10-5 kDa), APH-III (5-3 kDa), APH-IV (3-1 kDa), and APH-V (below 1 kDa) using an ultrafiltration (UF) membrane bioreactor system. The antioxidative activity of the APHs was investigated and compared with that of a natural antioxidant, α-tocopherol, used as a reference. The fraction, APH-V, exhibited the highest antioxidative activity was further purified using consecutive chromatographic methods on SP-Sephadex C-25 column, Sephadex G-25 column, and high-performance liquid chromatography (HPLC) on an octadecylsilane column. The sequence of the purified peptide was Leu-Pro-His-Ser-Gly-Tyr and molecular weight was 672 Da. In addition, the purified peptide scavenged 35% on hydroxyl radical at 53.6 μM using electron spin resonance (ESR) spectroscopy.