Angiotensin-converting enzyme-inhibitory peptides in Manchego cheeses manufactured with different starter cultures

Bioactive peptides in ovine and caprine cheeselike systems prepared with proteases from Cynara cardunculus

The potential angiotensin-converting enzyme (ACE)-inhibitory and antioxidant activities of peptides in water-soluble extracts, obtained from raw and sterilized ovine and caprine cheeselike systems coagulated with enzymes from the plant Cynara cardunculus, were assessed. Prior to the assay, the 3,000-Da permeate from 45-d-old cheeselike systems was fractionated by tandem chromatographic techniques. Several peaks were obtained in each chromatogram, but only some were associated with ACE-inhibitory or antioxidant activity or both. Peptides Tyr-Gln-Glu-Pro, Val-Pro-Lys-Val-Lys, and Tyr-Gln-Glu-Pro-Val-Leu-Gly-Pro-* from beta-casein, as well as Arg-Pro-Lys and Arg-Pro-Lys-His-Pro-Ile-Lys-His-* from alpha(s1)-casein exhibited ACE-inhibitory activity. Peptides released upon cleavage of the peptide bond Leu190-Tyr191 (either in ovine or caprine beta-casein), and corresponding to the beta-casein sequence Tyr-Gln-Glu-Pro-*, possessed antioxidant activity.

Occurrence of the angiotensin-converting enzyme inhibiting tripeptides Val-Pro-Pro and Ile-Pro-Pro in different cheese varieties of Swiss origin

The contents of the 2 antihypertensive peptides Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) were determined in 101 samples from 10 different Swiss cheese varieties using HPLC with subsequent triple mass spectrometry. In the category of extra hard and hard cheeses, the Protected Denomination of Origin cheeses Berner Alpkäse and Berner Hobelkäse, L'Etivaz à rebibes, Le Gruyère, Sbrinz, Emmentaler (organic and conventional) and in the category of semihard cheeses, the varieties Tilsiter, Appenzeller 1/4 fat and full fat, Tête de Moine, and Vacherin fribourgeois were screened in the study. The average concentration of the sum of VPP and IPP in the screened cheese varieties varied to a large extent, and substantial variations were obtained for individual samples within the cheese varieties. The lowest average concentration of the 2 tri-petides was found in L'Etivaz à rebibes (n = 3) at 19.1 mg/kg, whereas Appenzeller 1/4 fat (n = 4) contained the greatest concentration at 182.2 mg/kg. In individual samples, the total concentration of VPP and IPP varied between 1.6 and 424.5 mg/kg. With the exception of a 10-yr-old cheese, VPP was always present at greater concentrations than IPP. Milk pretreatment, cultures, scalding conditions, and ripening time were identified as the key factors influencing the concentration of these 2 naturally occurring bioactive peptides in cheese. The results of the present study show that various traditional cheese varieties contain, on average, similar concentrations of the 2 antihypertensive peptides to the recently developed fermented milk products with blood pressure-lowering property. This may serve as a basis for the development of a functional cheese with blood pressure-lowering property.

Vascular effects, angiotensin I-converting enzyme (ACE)-inhibitory activity, and antihypertensive properties of peptides derived from egg white

In this study, we have identified novel antihypertensive peptides derived from egg-white proteins. The sequences YRGGLEPINF and ESIINF produced an acute blood-pressure-lowering effect in spontaneously hypertensive rats upon a single oral administration. Our results suggest that the antihypertensive action could be attributed to a vascular-relaxing mechanism that would occur in vivo independently of angiotensin I-converting enzyme (ACE) inhibition, because neither these peptides nor their main digestion fragments, except for the dipeptide YR, acted as ACE inhibitors in vitro. The vasodilator and antihypertensive activity of the sequences ESI and NF would explain the blood-pressure-lowering effect of ESIINF. With regard to YRGGLEPINF, in addition to NF, YR appeared as the main fragment responsible for its activity. The dipeptide YR, named kyotorphin and previously identified as an endogenous analgesic neuropeptide in the central nervous system, showed strong vasodilator and antihypertensive properties. The structure-activity features of the vasodilator peptides are discussed.

Mass spectrometry in nutrition: understanding dietary health effects at the molecular level

In modern nutrition research, mass spectrometry has developed into a tool to assess health, sensory as well as quality and safety aspects of food. In this review, we focus on health-related benefits of food components and, accordingly, on biomarkers of exposure (bioavailability) and bioefficacy. Current nutrition research focuses on unraveling the link between dietary patterns, individual foods or food constituents and the physiological effects at cellular, tissue and whole body level after acute and chronic uptake. The bioavailability of bioactive food constituents as well as dose-effect correlations are key information to understand the impact of food on defined health outcomes. Both strongly depend on appropriate analytical tools to identify and quantify minute amounts of individual compounds in highly complex matrices--food or biological fluids--and to monitor molecular changes in the body in a highly specific and sensitive manner. Based on these requirements, mass spectrometry has become the analytical method of choice with broad applications throughout all areas of nutrition research. The current review focuses on selected areas of application: protein and peptide as well as nutrient and metabolite analysis.

Production of active angiotensin-I converting enzyme inhibitory peptides derived from bovine β-casein by recombinant DNA technologies

A wide range of anti-hypertensive peptides potentially able to lower blood pressure through the inhibition of vasoactive enzymes such as angiotensin-I converting enzyme (ACE) are known. Currently, ACE-inhibitory peptides can be produced from precursor proteins via enzymatic hydrolysis by proteolytic enzymes, or food fermentation with proteolytic starter cultures. These approaches are neither selective nor easy. In this study a novel procedure has been developed, based on recombinant DNA technologies, for the production of highly purified fractions of three polypeptides derived from bovine beta-casein active as ACE inhibitors in vitro. The procedure includes peptide expression in Escherichia coli cells as recombinant fusion proteins, purification by affinity chromatography, cleavage by proteinase from a selected strain of Lactobacillus helveticus and isolation of bioactive peptides (BPs). The reported concentration of inhibitor needed to reduce at 50% ACE activity (IC(50)) values for single BP calculated in inhibiting the ACE enzyme gave results in agreement with the same parameters available in literature for other milk-derived BPs. This procedure could be used to obtain quantities of pure peptides to determine their interactions with ACE, with the aim of designing peptides that have stronger inhibitory properties and exhibit new pharmacological profiles. Moreover, its scale up would be of commercial interest for the production of functional foods, e.g., milk beverages with blood pressure-lowering effects.

Vasodilator effects of peptides derived from egg white proteins

The aim of this work was to investigate the effect of several peptides, identified before and after simulated gastrointestinal digestion of an egg white hydrolysate, on the vascular function, in rat aorta. The sequences IVF, RADHPFL and YAEERYPIL (0.1 mM) induced vasodilatation in intact aortic rings, with the maximum percentage of dilation corresponding to RADHPFL (40.5+/-7.0%). Two of the end products of the gastrointestinal digestion, RADHP and YPI, also showed vasodilator activity with degrees of relaxation higher than 50%. However, all these peptides failed to induce relaxation in endothelium-denuded aortic rings. The relaxation induced by RADHP was concentration-dependent and it was partially blocked by the nitric oxide synthase inhibitor L-NAME (100 microM) and by the B(1) bradykinin receptor antagonist Des-HOE 140 (30 nM), thus showing that it was mediated by NO production through the activation of B(1) bradykinin receptors. These findings suggest that these peptides could reduce the vascular resistance and could be used as functional food ingredients in the prevention and treatment of hypertension.

Short-term effect of egg-white hydrolysate products on the arterial blood pressure of hypertensive rats

In the present study we evaluate the blood pressure-lowering effect of the following products: the hydrolysate obtained from egg white (EW) by enzymatic treatment with pepsin (HEW), the peptide fraction of HEW with molecular mass lower than 3000 Da (HEW<3000 Da), and three peptide sequences isolated from HEW<3000 Da (Tyr-Ala-Glu-Glu-Arg-Tyr-Pro-Ile-Leu: YAEERYPIL); (Arg-Ala-Asp-His-Pro-Phe-Leu: RADHPFL); and (Ile-Val-Phe (IVF)). These peptides, and also HEW and HEW<3000 Da, had been characterized previously in vitro as potent inhibitors of angiotensin-converting enzyme (ACE). EW and the products mentioned earlier were orally administered by gastric intubation, to 17–20-week-old male spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto (WKY) rats. We measured the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) of the rats by the tail cuff method before administration and also 2, 4, 6, 8 and 24h post-administration. Distilled water served as negative control, and we used captopril (50mg/kg) as positive control to carry out similar experiments with a known ACE inhibitor. HEW, HEW<3000 Da and the three peptide sequences decreased SBP and DBP in SHR but they did not modify these variables in WKY rats. The peptide sequences YAEERYPIL, RADHPFL and IVF showed a potency to decrease blood pressure greater than HEW or HEW<3000 Da. The results obtained suggest that the studied products could be used as a functional food with potential therapeutic benefit in the prevention and treatment of hypertension.

Antihypertensive Effect of Peptides Obtained from Enterococcus faecalis-Fermented Milk in Rats

Previous studies have demonstrated that milk fermented with Enterococcus faecalis decreases the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) of spontaneously hypertensive rats. In this study, we evaluated the antihypertensive activity of the following peptide sequences: LHLPLP, LHLPLPL, LVYPFPGPIPNSLPQNIPP, VLGPVRGPFP, and VRGPFPIIV. These peptides isolated from E. faecalis-fermented milk showed in vitro angiotensin I-converting enzyme-inhibitory activity. Because the most potent angiotensin I-converting enzyme-inhibitory sequences were LHLPLP and LVYPFPGPIPNSLPQ-NIPP, we administered different doses of these peptides to spontaneously hypertensive rats. High doses of the remaining sequences were also administered to these animals. Water served as a negative control and captopril as a positive control. All products were administered orally. The SBP and DBP were measured before administration and also at 2, 4, 6, 8, and 24 h after administration. Before administration of the different products, spontaneously hypertensive rats showed SBP and DBP values of 218 +/- 2.5 and 157 +/- 5.9 mmHg, respectively (n = 30). The sequences LHLPLP, LVYPF-PGPIPNSLPQNIPP, VLGPVRGPFP, and VRGPFPIIV caused clear and significant decreases in SBP, DBP, or both in the animals. In particular, the antihypertensive effect could be clearly established when 2 or 3 mg/kg of LHLPLP was administered. These 2 doses of LHLPLP showed similar antihypertensive properties. Four hours after administration of captopril or the highest doses of the different peptides, the decreases in the SBP and the DBP (mmHg) were as follows: captopril (SBP = 52 +/- 5.8, DBP = 38.8 +/- 3.8), 3 mg/kg of LHLPLP (SBP = 25.3 +/- 8.2, DBP = 29.5 +/- 7.6), 6 mg/kg of LVYPFPGPIP-NSLPQNIPP (SBP = 14.9 +/- 3.7, DBP = 8.7 +/- 4.4), 10 mg/kg of LHLPLPL (SBP = 7.7 +/- 4.1, DBP = 9.4 +/- 3.1), 10 mg/kg of VLGPVRGPFP (SBP = 16.2 +/- 5.8, DBP = 21.64 +/- 3.2), and 10 mg/kg of VRGPFPIIV (SBP = 16.05 +/- 2.74, DBP = 9.19 +/- 3.49). The results obtained suggest that the sequences LHLPLP, LVYPFPGPIPNSLPQ-NIPP, VLGPVRGPFP, and VRGPFPIIV could be responsible, at least in part, for the antihypertensive properties described for E. faecalis-fermented milk.

Antibacterial activities of peptides from the water-soluble extracts of Italian cheese varieties

Water-soluble extracts of 9 Italian cheese varieties that differed mainly for type of cheese milk, starter, technology, and time of ripening were fractionated by reversed-phase fast protein liquid chromatography, and the antimicrobial activity of each fraction was first assayed toward Lactobacillus sakei A15 by well-diffusion assay. Active fractions were further analyzed by HPLC coupled to electrospray ionization-ion trap mass spectrometry, and peptide sequences were identified by comparison with a proteomic database. Parmigiano Reggiano, Fossa, and Gorgonzola water-soluble extracts did not show antibacterial peptides. Fractions of Pecorino Romano, Canestrato Pugliese, Crescenza, and Caprino del Piemonte contained a mixture of peptides with a high degree of homology. Pasta filata cheeses (Caciocavallo and Mozzarella) also had antibacterial peptides. Peptides showed high levels of homology with N-terminal, C-terminal, or whole fragments of well known antimicrobial or multifunctional peptides reported in the literature: alphaS1-casokinin (e.g., sheep alphaS1-casein (CN) f22-30 of Pecorino Romano and cow alphaS1-CN f24-33 of Canestrato Pugliese); isracidin (e.g., sheep alphaS1-CN f10-21 of Pecorino Romano); kappacin and casoplatelin (e.g., cow kappa-CN f106-115 of Canestrato Pugliese and Crescenza); and beta-casomorphin-11 (e.g., goat beta-CN f60-68 of Caprino del Piemonte). As shown by the broth microdilution technique, most of the water-soluble fractions had a large spectrum of inhibition (minimal inhibitory concentration of 20 to 200 microg/mL) toward gram-positive and gram-negative bacterial species, including potentially pathogenic bacteria of clinical interest. Cheeses manufactured from different types of cheese milk (cow, sheep, and goat) have the potential to generate similar peptides with antimicrobial activity.

Angiotensin-Converting Enzyme Inhibitory Activity of Peptides Derived from Caprine Kefir

In this study, a potent angiotensin-converting enzyme (ACE)-inhibitory activity was found in a commercial kefir made from caprine milk. The low molecular mass peptides released from caseins during fermentation were mainly responsible for this activity. Sixteen peptides were identified by HPLC-tandem mass spectrometry. Two of these peptides, with sequences PYVRYL and LVYPFTGPIPN, showed potent ACE-inhibitory properties. The impact of gastrointestinal digestion on ACE-inhibitory activity of kefir peptides was also evaluated. Some of these peptides were resistant to the incubation with pepsin followed by hydrolysis with Corolase PP. The ACE-inhibitory activity after simulated digestion was similar to or slightly lower than unhydrolyzed peptides, except for peptide beta-casein f(47-52) (DKIHPF), which exhibited an activity 8 times greater after hydrolysis.

Identification and formation of angiotensin-converting enzyme-inhibitory peptides in Manchego cheese by high-performance liquid chromatography–tandem mass spectrometry

A total of 75 peptides included in the fraction with molecular mass below 3000 from an 8-month-old Manchego cheese could be identified using HPLC coupled on line to an ion trap mass spectrometer. Some previously described peptides with antihypertensive and/or angiotensin-converting enzyme (ACE)-inhibitory activity were detected. The formation of five active sequences was followed during cheese ripening in four different batches of Manchego cheese. Two experimental batches of Manchego cheese elaborated with selected bacterial strains with the aim of improve the organoleptic characteristics demonstrated also a good performance in the formation of peptides with ACE-inhibitory activity during cheese ripening.

Angiotensin I converting enzyme-inhibitory activity of bovine, ovine, and caprine kappa-casein macropeptides and their tryptic hydrolysates

This work evaluated the angiotensin-converting enzyme (ACE)-inhibitory activities of bovine, ovine, and caprine kappa-casein macropeptides (CMPs) and their tryptic hydrolysates. The results obtained indicate that bovine, ovine, and caprine CMPs exhibited moderate in vitro ACE-inhibitory activities that increased considerably after digestion under simulated gastrointestinal conditions. Active peptides could also be produced from CMPs via proteolysis with trypsin, with tryptic hydrolysates exhibiting a more extensive ACE-inhibitory activity than intact CMPs during simulated gastrointestinal digestion. Two active fractions were chromatographically separated from the tryptic hydrolysate of the bovine CMP, but their complexity hampered the assignment of the ACE-inhibitory activity to specific peptide sequences. Evidence for the release of the strong ACE-inhibitory tripeptide IPP was found upon simulation of the gastrointestinal digestion of peptides released by trypsin from the CMP sequence. These findings might help to promote further exploitation of cheese whey in the preparation of nutraceuticals for inclusion in the composition of functional food products with high added values.