Purification and characterization of antioxidative peptides derived from chicken skin gelatin hydrolysate

The aim was to determine the antioxidative activity of novel chicken skin gelatin peptides and their mechanism of action. Peptides were obtained by hydrolysis of chicken skin gelatin with alcalase, pronase E and collagenase enzymes combined with ultrafiltration using 10, 5 and 2 KDa MWCO membranes respectively, followed by fractionation and purification by gel filtration. The antioxidant activities of isolated peptides were investigated by monitoring hydroperoxides using the ferric thiocyanate method and malonaldehyde (MDA) by the TBARS method in an oxidizing linoleic acid model system. The highest antioxidative activity among the three hydrolysates fractions was observed in the lowest molecular weight chicken skin hydrolysate (< 2 KDa). After further purification by gel filtration, QTOF mass spectroscopy revealed that the molecular weight of chicken gelatin peptides was in the range 200-800 Da (corresponding to 2-8 amino acids). The hydroxyl radical activity, superoxide anion radical activity and Fe(2+)chelating activity indicated that purified chicken peptide (10 mg/ml) possessed greater antioxidative activity compared with the commercial antioxidants BHT, trolox and ascorbic acid (10 mg/ml). Amino acid composition of chicken gelatin hydrolysates exhibited a high content of Gly, Pro and H.Pro and hydrophobic amino acids. However, further purification by gel filtration gave chicken gelatin peptide fractions rich in hydroxyproline (11.57%), glycine (33.49%), alanine (7.78%), proline (15.07%), and lysine (12.87%). Clearly, the higher content of lysine, imino acids proline and hydroxyproline and hydrophobic amino acids as well as low MW contributed to the high antioxidant activity of the peptide.