Antioxidant and ACE Inhibitory Bioactive Peptides Purified from Egg Yolk Proteins.

Marwa Yousr,Nazlin Howell

doi:10.3390/ijms161226155

Abstract

Protein by-products from the extraction of lecithin from egg yolk can be converted into value-added products, such as bioactive hydrolysates and peptides that have potential health enhancing antioxidant, and antihypertensive properties. In this study, the antioxidant and angiotensin converting enzyme (ACE) inhibitory activities of peptides isolated and purified from egg yolk protein were investigated. Defatted egg yolk was hydrolyzed using pepsin and pancreatin and sequentially fractionated by ultrafiltration, followed by gel filtration to produce egg yolk gel filtration fractions (EYGF). Of these, two fractions, EYGF-23 and EYGF-33, effectively inhibited the peroxides and thiobarbituric acid reactive substance (TBARS) in an oxidizing linoleic acid model system. The antioxidant mechanism involved superoxide anion and hydroxyl radicals scavenging and ferrous chelation. The presence of hydrophobic amino acids such as tyrosine (Y) and tryptophan (W), in sequences identified by LC-MS as WYGPD (EYGF-23) and KLSDW (EYGF-33), contributed to the antioxidant activity and were not significantly different from the synthetic BHA antioxidant. A third fraction (EYGF-56) was also purified from egg yolk protein by gel filtration and exhibited high ACE inhibitory activity (69%) and IC50 value (3.35 mg/mL). The SDNRNQGY peptide (10 mg/mL) had ACE inhibitory activity, which was not significantly different from that of the positive control captopril (0.5 mg/mL). In addition, YPSPV in (EYGF-33) (10 mg/mL) had higher ACE inhibitory activity compared with captopril. These findings indicated a substantial potential for producing valuable peptides with antioxidant and ACE inhibitory activity from egg yolk.

Highlights

Scientific research has focused heavily on evaluating the nutritional value of the hen’s eggs
In addition to the high nutritional value, egg yolk is an important source of lecithin, which is widely used as a surfactant, a lubricant and as an emulsifying agent in pharmaceutical and industrial applications [1]
egg yolk gel filtration fractions (EYGF)-23 and EYGF-33 inhibited oxidation induced in a linoleic acid oxidizing model system by a variety of mechanisms indicating their potential to function in diverse oxidizing environments

Summary

Introduction

Scientific research has focused heavily on evaluating the nutritional value of the hen’s eggs. The waste products that result from the extraction of lecithin from egg yolk are potentially valuable by-products as they contain a substantial amount of protein, which represents approximately 30% of dried egg yolk This protein could be converted into value-added bioactive peptides by enzymatic hydrolysis; there are very few reported studies on the utilization of the egg yolk protein by-product. Bioactive peptides usually contain 2–20 amino acid residues per molecule, and are released upon enzymatic hydrolysis, during food processing or during gastrointestinal digestion [2]. These peptides may exert diverse physiological effects, such as antihypertensive, antimicrobial, antithrombotic, hypocholesterolaemic, and antioxidant actions [2,3,4,5] due to the amino acid composition, sequence, and molecular weight [6]. Two aspects of the diverse function of bioactive peptides were studied to enhance nutritional properties of food, i.e., by improving the preservation and nutritional value by reducing lipid oxidation and by enhancing health benefits by acting as a potential angiotensin converting enzyme (ACE) inhibitor

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Conclusion