ACE-Inhibitory and Radical-Scavenging Activity of Peptides Derived from -Lactoglobulin f(19-25). Interactions with Ascorbic Acid BLANCA HERNA Ä NDEZ-LEDESMA,LOURDES AMIGO,ISIDRA RECIO, AND BEGON ˜ A BARTOLOME Ä * Instituto de Fermentaciones Industriales (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain In this work, the angiotensin-converting enzyme (ACE)-inhibitory and radical-scavenging activities of the -lactoglobulin (-Lg)-derived peptides WY f(19-20), WYS f(19-21), WYSL f(19-22), WYSLA f(19-23), WYSLAM f(19-24), and WYSLAMA f(19-25) have been determined. The ACE-inhibitory activity (IC 50 ) varied from 38.3 to 90.4 µM, with the exception of WYS (>500 µM). All -Lg-derived peptides also exhibited radical-scavenging activity (oxygen radical absorbance capacity (ORAC) values ranged from 4.45 to 7.67 µmol Trolox equivalents/µmol of peptide). The presence and position of amino acids Trp, Tyr, and Met were proposed to be responsible for the antioxidant activity. The equimolar amino acid mixtures of all the peptides showed ORAC values lower than those of the corresponding peptides, indicating that the peptidic bond or the structural conformation had a positive influence on this activity. Finally, positive antioxidant effects of WYS, WYSL, and WYLA with ascorbic acid were observed, whereas WY and WYSLAM showed negative effects, both cases for different molar ratio mixtures. These results should be taken into account in the development of new food ingredients on the basis of peptides from -Lg. KEYWORDS: -Lactoglobulin peptides; ACE-inhibitory activity; radical-scavenging activity; ORAC; ascorbic acid INTRODUCTION -Lactoglobulin (-Lg) comprises 60% of whey protein. It is known to exert a wide range of nutritional, functional, and biological activities that makes it a potential ingredient for health-promoting foods, drugs, and cosmetics (1). In addition to the bioactivities exerted by the native molecule, -Lg may exhibit further physiological functions because of numerous bioactive peptides that are contained within the protein. Several bioactive sequences derived from this whey protein have been identified and their antihypertensive, opioid, antimicrobial, antithrombotic, mineral-binding, immunomodulant, and hypo- cholesterolaemic properties have been reported (2-5). Free-radical-mediated lipid oxidation is considered to be one of the main limiting factors for the quality and acceptability of foods during processing and storage. Currently, synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are commonly used to act against free radicals in food and biological systems. However, the potential adverse effects of these synthetic additives have stimulated their replacement by natural antioxidants derived from dietary sources (6). Moreover, reactive radicals are implicated in the ethiology of age-associated chronic diseases such as cardiovascular diseases, neurodegenerative disorders, diabetes, and certain types of cancer (7). The utilization of protein hydrolysates or peptides to improve the antioxidant activity in functional foods presents additional advantages over other natural antioxidants, since they also confer an additional nutritional value, as well as other desired functional properties. In the past few years, the search for whey-derived peptides with radical-scavenging and lipid peroxidation inhibitory activities is receiving special attention. Recent studies have described the antioxidant activity of whey protein hydrolyzates (8, 9). However, few data on the antioxidant properties of the individual peptides released after whey protein hydrolysis are available. Peptide Trp-Tyr-Ser-Leu-Ala-Met-Ala-Ala-Ser-Asp-Ile (WYS- LAMAASDI, f19-29) derived from -Lg after hydrolysis with Corolase PP has shown a relatively large scavenging radical activity (10). Since whey peptides may be present in foods together with other antioxidants, all implicated in multiple redox reactions, it would be interesting to study the potential positive effects of these -Lg-derived peptides with other nonpeptidic antioxidant agents. Positive effects have previously been demonstrated with R-tocopherol and peptides derived from enzymatic hydrolyzates of soybean protein (11) and yellowfin sole (12). Antioxidant deficiency has been implicated in the occurrence of hypertension. Antioxidant-rich diets have been shown to * To whom correspondence should be addressed. Tel.: +34 91 5622900. Fax: +34 91 5644853. E-mail: bartolome@ifi.csic.es. 3392 J. Agric. Food Chem. 2007, 55, 3392-3397 10.1021/jf063427j CCC: $37.00 © 2007 American Chemical Society Published on Web 04/06/2007 Downloaded by KING MONGKUT UNIV TECH THONBUR on September 11, 2009 | http://pubs.acs.org Publication Date (Web): April 6, 2007 | doi: 10.1021/jf063427j