Structural characterization of peroxyl radical oxidative products of antioxidant peptides from hydrolyzed proteins.

This work aimed to characterize oxidative products of five unique antioxidant peptides (P1: YFDEQNEQFR, P2: GQLLIVPQ, P3: SPFWNINAH, P4: NINAHSVVY, P5: RALPIDVL) from hydrolyzed oat proteins. Peptides were reacted with 2,2'-Azobis(2-amidinopropane) dihydrochloride, a common peroxyl radical generator. Chromatographic data showed that peptide P3 was the most oxidized (67 ± 4 %) while also displaying the most ability to scavenge radicals in the oxygen absorbance capacity assay (ORAC) with an activity of 2.16 ± 0.09 µM Trolox equivalents/µM peptide. Structural characterization using mass spectrometry showed the presence of four oxidative products of P3, three of which were mono-oxygenated and the fourth di-oxygenated. The identification of these oxidative products is new and provides an opportunity to investigate their biological function. A good correlation (r = 0.889) between the degree of oxidation and the ORAC data, demonstrates the usefulness of using oxidative peptide data to predict their radical scavenging activities.

Antioxidant, pancreatic lipase, and α-amylase inhibitory properties of oat bran hydrolyzed proteins and peptides.

This work aimed to determine the antioxidant properties of identified hydrolyzed oat proteins and peptides, and their capacity to inhibit lipase and α-amylase. The protein hydrolysates retarded the oxidation of peanut oil by reducing peroxide values (up to 2.5-fold), relative to the control oil. Of the five tested peptides, P1 (YFDEQNEQFR), P3 (SPFWNINAH), and P4 (NINAHSVVY) significantly reduced the oxidation of linoleic acid. In the enzyme assays, P3 was the best lipase inhibitor (IC50 85.4 ± 3 µM) while P1 was the most potent inhibitor of α-amylase (IC50 37.5 ± 1.1 µM). The structure-activity relationship assessed using the CABS-dock computational model predicted that interactions between peptides and pancreatic lipase residues of Ser153 , His264 , and Asp177 were important for the inhibition. In the case of α-amylase, interactions with residues of the active sites (Asp197 , Glu233 , and Asp300 ), but not those of calcium- or chloride-binding domains, were important for the inhibition. PRACTICAL APPLICATIONS: In recent years, there have been many studies focussing on isolating multifunctional peptides from food and food waste with antioxidant and bioactivity potential to promote human health. Some of these antioxidant peptides have been found to be effective to prevent diseases and complications such as hypertension, cardiovascular disease, cancer, diabetes, and obesity. The peptides studied in this work showed a great potential to prevent oxidation in a lipid system and demonstrated a significant ability to reduce the enzymatic activity of lipase and α-amylase. These enzymes contribute to the digestion of fat and carbohydrate, and their inhibition can reduce the absorption of these macronutrients and make them a great target for designing antioxidant and anti-obesity compounds. With the multifunctional activity of oat bran-derived peptides, it is proposed that these peptides can be used in food formulations due to their antioxidant and potential anti-obesity properties.

Chromium and arsenic speciation analysis in meats by HPLC-ICP-MS in the presence of hydrolyzed oat proteins with radical scavenging activities.

Transition metals play an important role in a wide variety of biological processes, but their functions are dependent on the quantity and the type of species present. Specific forms of arsenic (As) and chromium (Cr) are associated with oxidative stress, cellular damage and inflammation. The aim of this research was to test in a food system whether, in the presence of hydrolyzed oat proteins, arsenic or chromium will exist predominantly in a specific oxidative state, and to evaluate the potential implication of promoting or decreasing oxidative stress. Eight hydrolyzed proteins with different degrees of radical scavenging activities were produced by combining two extraction methods and four proteases. The addition of hydrolysates to ground chicken meat decreased lipid hydroperoxides by up to 50% when stored at 4 °C but had no effect at -20 °C. The ratio of pentavalent arsenic (As(V)) to arsenobetaine (AsB) in meat was about 2:1 but in the presence of the hydrolysates, meanwhile, the amount of AsB detected was 3-fold higher depending on the storage condition. This was due to better extraction of AsB in the presence of hydrolysates rather than to the conversion of other species. Data on chromium showed that Cr(VI) contents decreased from 14.3 ± 0.1 to 6.3 ± 0.5 µg/g while concentrations of Cr(III) increased from 2.8 ± 0. 2 to 8.6 ± 0.7 µg/g. In summary, the addition of hydrolyzed oat proteins to chicken meat enhanced the extraction of AsB, and had little effect on arsenic speciation during storage meanwhile, there was a reduction of Cr(VI) to Cr(III) which was in part due to the relative content of thiol groups. Additionally, there was a reduction of lipid oxidation in meats that contained the oat protein hydrolysates.

Antioxidant properties and potential mechanisms of hydrolyzed proteins and peptides from cereals.

Cereals like wheat, rice, corn, barley, rye, oat, and millet are staple foods in many regions around the world and contribute to more than half of human energy requirements. Scientific publications contain evidence showing that apart from energy, the regular consumption of whole grains is useful for the prevention of many chronic diseases associated with oxidative stress. Biological activities have mostly been attributed to the presence of glucans and polyphenols. In recent years however, food proteins have been investigated as sources of peptides that can exert biological functions, promote health and prevent oxidative stress. This review focuses on the role of hydrolyzed proteins and peptides with antioxidant properties in various models and their mechanisms which include hydrogen or electron transfer, metal chelating, and regulation of enzymes involved in the oxidation-reduction process.

Antioxidant and Anti-Apoptotic Properties of Oat Bran Protein Hydrolysates in Stressed Hepatic Cells.

The objective of this work was to find out how the method to extract proteins and subsequent enzymatic hydrolysis affect the ability of hepatic cells to resist oxidative stress. Proteins were isolated from oat brans in the presence of Cellulase (CPI) or Viscozyme (VPI). Four protein hydrolysates were produced from CPI and four others from VPI when they treated with Alcalase, Flavourzyme, Papain, or Protamex. Apart from CPI-Papain that reduced the viability of cell by 20%, no other hydrolysate was cytotoxic in the hepatic HepG2 cells. In the cytoprotection test, VPI-Papain and VPI-Flavourzyme fully prevented the damage due to peroxyl radical while CPI-Papain and CPI-Alcalase enhanced the cellular damage. Cells treated with VPI-hydrolysates reduced intracellular reactive oxygen species (ROS) by 20-40% and, also increased the intracellular concentration of glutathione, compared to CPI-hydrolysates. In antioxidant enzyme assays, although all hydrolysates enhanced the activity of both superoxide dismutase and catalase by up to 2- and 3.4-fold, respectively relative the control cells, the largest increase was due to VPI-Papain and VPI-Flavourzyme hydrolysates. In caspase-3 assays, hydrolysates with reduced ROS or enhanced antioxidant enzyme activities were able to reduce the activity of the pro-apoptotic enzyme, caspase-3 indicating that they prevented oxidative stress-induced cell death.

Peptidomic analysis of hydrolyzed oat bran proteins, and their in vitro antioxidant and metal chelating properties.

Peptide profiles of hydrolyzed oat proteins and the susceptibility of their polypeptides to proteolytic cleavages were determined using peptidomic analysis. In addition, antioxidant activities were also measured. Proteins isolates were first extracted with carbohydrases, Viscozyme or Cellulase and then hydrolyzed with proteases (Alcalase, Papain, Protamex, Flavourzyme). Amongst the eight hydrolysates, Viscozyme-proteins hydrolyzed with Papain showed the highest ability to quench ABTS+ radicals (866.9 ±â€¯10.6 µM TE/g) and to chelate ferrous ions (75 ±â€¯0.4%) while displaying the second strongest activity for ROO radicals (396.7 ±â€¯14.0 µM TE/g). Peptidomics analysis showed that the higher activity of papain hydrolysate in most assays was related to its greater proteolytic action on main proteins (avenin, 11S- and 12S-globulins) compared to other proteases. In addition, the number of peptides identified in the Papain digest of proteins extracted with Viscozyme was about half relative to the number in proteins from bran treated with Cellulase and digested with the same protease. This was likely because the carbohydrases differently affected polypeptide secondary structures.

Potential of Food Hydrolyzed Proteins and Peptides to Chelate Iron or Calcium and Enhance their Absorption.

Iron and calcium are two essential micronutrients that have strong effects on nutrition and human health because of their involvement in several biological and redox processes. Iron is responsible for electron and oxygen transport, cell respiration, and gene expression, whereas calcium is responsible for intracellular metabolism, muscle contraction, cardiac function, and cell proliferation. The bioavailability of these nutrients in the body is dependent on enhancers and inhibitors, some of which are found in consumed foods. Hydrolyzed proteins and peptides from food proteins can bind these essential minerals in the body and facilitate their absorption and bioavailability. The binding is also important because excess free iron will increase oxidative stress and the risks of developing chronic diseases. This paper provides an overview of the function of calcium and iron, and strategies to enhance their absorption with an emphasis on hydrolyzed proteins and peptides from foods. It also discusses the relationship between the structure of peptides and their potential to act as transition metal ligands.

Antioxidant Activity of Oat Proteins Derived Peptides in Stressed Hepatic HepG2 Cells.

The purpose of this study was to determine, for the first time, antioxidant activities of seven peptides (P1-P7) derived from hydrolysis of oat proteins in a cellular model. In the oxygen radical absorbance capacity (ORAC) assay, it was found that P2 had the highest radical scavenging activity (0.67 ± 0.02 µM Trolox equivalent (TE)/µM peptide) followed by P5, P3, P6, P4, P1, and P7 whose activities were between 0.14-0.61 µM TE/µM). In the hepatic HepG2 cells, none of the peptides was cytotoxic at 20-300 µM. In addition to having the highest ORAC value, P2 was also the most protective (29% increase in cell viability) against 2,2'-azobis(2-methylpropionamidine) dihydrochloride -induced oxidative stress. P1, P6, and P7 protected at a lesser extent, with an 8%-21% increase viability of cells. The protection of cells was attributed to several factors including reduced production of intracellular reactive oxygen species, increased cellular glutathione, and increased activities of three main endogenous antioxidant enzymes.