This work reports the antioxidant activity of peptides produced by enzymatic hydrolysis of crude egg white with pepsin. Four peptides included in the protein sequence of ovalbumin possessed radical scavenging activity higher than that of Trolox. The hydrolysate of egg white with pepsin for 3 h was previously found to exhibit a strong angiotensin I-converting enzyme (ACE) inhibitory activity in vitro. The combined antioxidant and ACE inhibition properties make it a very useful multifunctional preparation for the control of cardiovascular diseases, particularly hypertension. No correlation was found between antioxidant and ACE inhibitory activities. However, the peptide Tyr-Ala-Glu-Glu-Arg-Tyr-Pro-Ile-Leu, which was a strong ACE inhibitor (50% inhibitory concentration, 4.7 microM) also exhibited a high radical scavenging activity (oxygen radical absorbance capacity-fluorescein value, 3.8 micromol of Trolox equivalent per micromol of peptide) and delayed the low-density lipoprotein lipid oxidation induced by Cu2+ at a concentration of approximately 0.16 mg/mg of low-density lipoprotein. Present results support that antioxidant peptides and amino acids not only act individually, but also cooperatively and synergistically.

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The hydrolysis of crude egg white with pepsin, trypsin, and chymotrypsin produced peptides with angiotensin-converting enzyme (ACE) inhibitory properties. These peptides were mainly derived from the proteolysis of ovalbumin. The most active hydrolysates were obtained after treatment with pepsin (50% inhibitory concentration [IC50], 55.3 microg/ml), with the fraction having a molecular mass lower than 3,000 Da giving the highest ACE inhibitory activity (IC50, 34.5 microg/ml). Nine subfractions were collected from the fraction with a molecular mass lower than 3,000 Da using semipreparative reversed-phase high-performance liquid chromatography. Considerable ACE inhibitory activity (IC50 < 40 microg/ml) was found in three of them. These subfractions were analyzed by reversed-phase high-performance liquid chromatography-tandem mass spectrometry, and 14 peptides were identified. These sequences were synthesized, and their ACE inhibitory activities were measured. Among the identified peptides, two novel sequences with potent ACE inhibitory activity were found. The amino acid sequences of these inhibitors were identified as Arg-Ala-Asp-His-Pro-Phe-Leu and Tyr-Ala-Glu-Glu-Arg-Tyr-Pro-Ile-Leu and showed IC50 values of 6.2 and 4.7 microM, respectively.

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