Isolation, purification, and structure identification of antioxidant peptides from embryonated eggs.

Antioxidant peptides are increasingly attracting researchers in medicine and foods. In the present study, egg white hydrolysates of embryonated eggs hatched on the sixth day (EWHD) were segmented consecutively by ultrafiltration membranes with small tangential flow ultrafiltration system. Four segments with more than 30, 30 to 10 kDa, 10 to 5 kDa, and less than 5 kDa of molecular weight cut-off (MWCO) values were separated and were labeled as MWCOI, MWCOII, MWCOIII, and MWCOIV, respectively. The antioxidant activities of segments were investigated by performing DPPH•, •OH radical scavenging, ultra oxygen anion (O2-•), total antioxidant capacity, and reducing power experiments. The results indicated that MWCOI has the strongest scavenging activities on DPPH• radical. However, MWCOIV has the strongest scavenging activities on •OH, O2-•, total antioxidant capacity, and reducing power, which revealed that MWCOIV has strong antioxidant activity. MWCOIV was further separated into 14 fractions via semipreparative reverse-phased high-performance liquid chromatography (RP-HPLC), and their antioxidant activity was evaluated by different antioxidant assays in vitro. The fractions 10 and 7 had strong antioxidant activities. The purities of these 2 fractions were determined by analytical RP-HPLC. Moreover, both fractions 10 and 7 displayed high purity levels, and they were identified by quadrupole time-of-flight tandem mass spectrometry. Only fraction 10, with a molecular weight of 204 Da, can be identified to be Ser-Val. EWHD can be considered as a promising source of natural food antioxidants for the development of functional food.

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