Characterization of a novel antioxidant peptide from feather keratin hydrolysates

Feather hydrolysates were obtained through submerged cultivation of 50 g/L feathers with Chryseobacterium sp. kr6. Culture supernatants, displaying antioxidant properties, as evaluated by the 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radical scavenging method, were partially purified by gel-filtration chromatography. Fractions showing scavenging activity were pooled, lyophilized and tested at different concentrations (0.1-1.0 mg/mL) by the total reactive antioxidant potential (TRAP) method, showing promising antioxidant capacities. Antioxidant activities of the partially purified feather hydrolysate (PPFH; 24.5 μg) were demonstrated by its ability to scavenge hydroxyl radicals and to inhibit lipid peroxidation. In addition, PPFH (0.24-24.5 μg) was found to reduce ferric ion (Fe3+), but did not display Fe2+-chelating activity. Thus, the main antioxidant activities could be related to the donation of hydrogen atoms, electron transfer and scavenging of hydroxyl radicals. PPFH was analyzed by mass spectrometry and five peptides were identified and chemically synthesized. The antioxidant activity of one peptide LPGPILSSFPQ was confirmed by ABTS and TRAP. The structure of this keratin-derived bioactive peptide has not been previously described.