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The stomach is a bioreactor and an important intersection of biochemical reactions that affect human health. Lipid peroxidation of meat in the stomach medium generates malondialdehyde (MDA), which is absorbed from the gut into human plasma and modifies low-density lipoprotein (LDL) to MDA-LDL. We found in the stomach medium (pH 3.0) a high antioxidant activity of vitamin E against meat lipid peroxidation, almost 35-fold higher than at pH 6.3. In the stomach medium, the antioxidant activity of vitamin E on meat lipid peroxidation was 20-fold higher than that of catechin. Vitamin E, at pH 3.0, acts synergistically with metmyoglobin (MbFe

Nitrite is added to meat products as a preservative and it acts as a bacteriostatic compound against Clostridium botulinum growth. Nitric-oxide (˙NO), myoglobin and S-nitroso-compounds seem to be the main molecules generated from nitrite in meat products, which by decomposition to ˙NO, form the main anti-clostridial factor. The growth of C. sporogenes from activated spores in the presence of 0.5–2.5 mM NAC–SNO was compared to nitrite, both at 37 °C for 5 days and at room temperature for 28 days. The present study demonstrates that NAC–SNO under the same conditions and concentrations, in meat products, acts as an anti-clostridial compound similar to nitrite. In contrast to nitrite which must be activated in meat by heating, NAC–SNO generates the anti-clostridial factor directly, without heating, as was evaluated in an unheated bacteriological medium. The toxic effect of NAC–SNO and nitrite in methaemoglobinaemia and generation of N-nitrosamines in vivo, in mice, were also determined. Mice were gavage fed milk containing 45 mg per kg per bw of nitrite or an equimolar equivalent of NAC–SNO in the presence of 50 mg per kg per bw of N-methylaniline. Nitrite generated methaemoglobinaemia and carcinogenic N-nitrosoamines (N-nitrosomethylaniline); however, NAC–SNO under the same conditions and concentrations generates much less methaemoglobin and no detectable N-nitrosoamines in the blood, in vivo.

Red-meat lipid peroxidation in the stomach results in postprandial oxidative stress (POS) which is characterized by the generation of a variety of reactive cytotoxic aldehydes including malondialdehyde (MDA). MDA is absorbed in the blood system reacts with cell proteins to form adducts resulting in advanced lipid peroxidation end products (ALEs), producing dysfunctional proteins and cellular responses. The pathological consequences of ALEs tissue damage include inflammation and increased risk for many chronic diseases that are associated with a Western-type diet. In earlier studies we used the simulated gastric fluid (SGF) condition to show that the in vitro generation of MDA from red meat closely resembles that in human blood after consumption the same amount of meat. In vivo and in vitro MDA generations were similarly suppressed by polyphenol-rich beverages (red wine and coffee) consumed with the meal. The present study uses the in vitro SGF to assess the capacity of more than 50 foods of plant origin to suppress red meat peroxidation and formation of MDA. The results were calculated as reducing POS index (rPOSI) which represents the capacity in percent of 100 g of the food used to inhibit lipid peroxidation of 200 g red-meat a POSI enhancer (ePOSI). The index permitted to extrapolate the need of rPOSI from a food alone or in ensemble such Greek salad, to neutralize an ePOSI in stomach medium, (ePOS–rPOSI=0). The correlation between the rPOSI and polyphenols in the tested foods was R2=0.75. The Index was validated by comparison of the predicted rPOSI for a portion of Greek salad or red-wine to real inhibition of POS enhancers. The POS Index permit to better balancing nutrition for human health., Graphical Abstract, Highlights • Absorption of diet MDA and ALEs in blood could induce risk factors for CVD and other diseases. • Red-meat generated MDA and ALEs in SGF are defined as ePOSI. • Reducing agents present in plant foods, reduced MDA and ALEs in SGF, are defined as rPOSI. • Calculated plant reducing agents by rPOSI was found to highly predict the reducing of ePOSI. • The POS index would help to quantify nutrition for promoting human health.

Samples of radiation-sterilized mechanically deboned turkey meat were inoculated with a strain of Campylobacter jejuni , stored at 5°C, and viable counts of the test organism determined during a 7-week period. As compared to results obtained with unsupplemented samples, addition of ascorbic acid or sodium isoascorbate (erythorbate) to the meat, at a concentration of 5 mmol/kg, caused an increase in the death rate of C. jejuni . Autooxidation of these compounds, during storage of the meat, supports the view that their toxic effect is mainly due to their oxidation products.

Nitrite reacts with secondary amines to form N-nitrosamines (N-NA), which lead to gastrointestinal cancers. The aim of this study was to compare nitrite with S-nitrosocysteine (Cys-SNO) and S-nitroso-N-acetylcysteine (NAC-SNO) with respect to N-NA formation, which was evaluated by determining the conversion of N-methylaniline to N-nitrosomethylaniline. Under neutral and acidic pH conditions, N-NA formation rate was nitrite > Cys-SNO > NAC-SNO. In the presence of copper or nucleophiles, NAC-SNO generated much less N-NA than Cys-SNO. Nitrite and Cys-SNO produced higher amounts of N-NA in the presence of oxygen, whereas NAC-SNO was almost oxygen insensitive. In meat in the stomach medium, NAC-SNO produced much lower amounts of N-NA than other additives. In heated meat, Cys-SNO and NAC-SNO generated the nitrosyl-hemochrome pink pigment, better than nitrite. In conclusion, NAC-SNO was much less reactive for N-NA formation than nitrite and Cys-SNO in conditions relevant to meat production and stomach digestion.

Red meat is an integral part of the Western diet, and high consumption is associated with an increased risk of chronic diseases. Using a system that simulated the human stomach, red meat was interacted with different oils (olive/fish) and lipid peroxidation was determined by measuring accumulation of malondialdehyde (MDA) and lipid peroxides (LOOH). Olive oil decreased meat lipid peroxidation from 121.7 ± 3.1 to 48.2 ± 1.3 μM and from 327.1 ± 9.5 to 77.3 ± 6.0 μM as assessed by MDA and ROOH, respectively. The inhibitory effect of olive oil was attributed to oleic acid rather than its polyphenol content. In contrast, fish oils from tuna or an ω-3 supplement dramatically increased meat lipid peroxidation from 96.2 ± 3.6 to 514.2 ± 6.7 μM MDA. Vitamin E inhibited meat lipid peroxidation in the presence of olive oil but paradoxically increased peroxidation in the presence of fish oil. The inhibitory properties of oleic acid may play a key role in the health benefits of the Mediterranean diet.

Food may undergo enhanced oxidation in the stomach leading to increases in the generation of deleterious lipid peroxidation products. Following meat consumption an escalation occurs in malondialdehyde (MDA) levels in human plasma. It was hypothesized that MDA could cause postprandial LDL modification in vivo , which can be abolished by the simultaneous addition of red wine polyphenols. Healthy volunteers consumed two test meals for four sequential days: meat cutlets (MC) and meat cutlets with red wine (MCRW). Postprandial plasma MDA levels after meal (MC) increased by 106 nmol/ml, and only by 57 nmol/ml after meal (MCRW). Following meal (MC) day 1 postprandial MDA–LDL levels increased by 27%. Following 4 days of repeated consumption of meal (MC), postprandial MDA–LDL levels increased by 96% ( P = 0.021) and remained elevated after an overnight fast. Addition of red wine to the meal (MCRW) completely prevented postprandial MDA–LDL modification. It is concluded that the postprandial increase level of MDA in the plasma is partially responsible for LDL modification.

Recent studies dramatically showed that the removal of circulating modified low-density lipoprotein (LDL) results in complete prevention of atherosclerosis. The gastrointestinal tract is constantly exposed to food, some of it containing oxidized compounds. Lipid oxidation in the stomach was demonstrated by ingesting heated red meat in rats. Red wine polyphenols added to the rats' meat diet prevented lipid peroxidation in the stomach and absorption of malondialdehyde (MDA) in rat plasma. In humans, postprandial plasma MDA levels rose by 3-fold after a meal of red meat cutlets. MDA derived from meat consumption caused postprandial plasma LDL modification in human. The levels of plasma MDA showed a 75% reduction by consumption of red wine polyphenols during the meat meal. Locating the main biological site of action of polyphenols in the stomach led to a revision in the understanding of how antioxidants work in vivo and may help to elucidate the mechanism involved in the protective effects of polyphenols in human health.

Polyphenols, which occur both in edible plants and in foodstuff, have been reported to exert a wide range of health effects; however, the mechanism of action of these molecules is not fully understood. One important cellular pathway affected by polyphenols is the activation of the transcription factor Nrf2 via the electrophile response element, which mediates generation of phase 2 detoxifying enzymes. Our study found that Nrf2 nuclear translocation and the activity of NAD(P)H quinone oxidoreductase (NQO1) were increased significantly after treatment of astrocytes with tert-butylhydroquinone (tBHQ), resveratrol, or curcumin, at 20-50μM. Incubation of tBHQ, resveratrol, and curcumin in the growth medium in the absence of astrocytes caused the accumulation of H(2)O(2). Treatment of cells with either glutathione or metmyoglobin was found to decrease Nrf2 translocation and NQO1 activity induced by polyphenols by up to 40 and 60%, respectively. Addition of both glutathione and metmyoglobin to growth medium decreased Nrf2 translocation and NQO1 activity by up to 100 and 80%, respectively. In conclusion, because metmyoglobin, in the presence of polyphenols and glutathione, is known to interact with H(2)O(2), semiquinones, and quinones, the up-regulation of the antioxidant defense of the cells through activation of the Nrf2 transcription factor, paradoxically, occurs via the generation of H(2)O(2) and polyphenol-oxidized species generated from the exogenous microenvironment of the cells.

Lipid oxidation in foods is one of the major degradative processes responsible for losses in food quality. The oxidation of unsaturated fatty acids results in significant generation of dietary advanced lipid oxidation endproducts (ALEs) which are in part cytotoxic and genotoxic compounds. The gastrointestinal tract is constantly exposed to dietary oxidized food compounds, after digestion a part of them are absorbed into the lymph or directly into the blood stream. After ingestion of oxidized fats animals and human have been shown to excrete in urine increase amounts of malondialdehyde but also lipophilic carbonyl compounds. Oxidized cholesterol in the diet was found to be a source of oxidized lipoproteins in human serum. Some of the dietary ALEs, which are absorbed from the gut to the circulatory system, seems to act as injurious chemicals that activate an inflammatory response which affects not only circulatory system but also organs such as liver, kidney, lung, and the gut itself. We believe that repeated consumption of oxidized fat in the diet poses a chronic threat to human health. High concentration of dietary antioxidants could prevent lipid oxidation and ALEs generation not only in foods but also in stomach condition and thereby potentially decrease absorption of ALEs from the gut. This could explains the health benefit of diets containing large amounts of dietary antioxidants such those present in fruits and vegetables, or products such as red-wine or tea consuming during the meal.

Current evidence supports a contribution of polyphenols to the prevention of cardiovascular disease, but their mechanisms of action are not understood. We investigated the impact of red wine polyphenols on postprandial cytotoxic lipid peroxidation products (MDA) levels in humans. In a randomized, crossover study, the effect of red wine polyphenols on postprandial levels of plasma and urine MDA was investigated. Three meals of 250 g turkey cutlets supplemented by water (A); soaked in red wine after heating plus 200 ml of red wine (B); or soaked in red wine prior to heating plus 200 ml of red wine (C) were administered to 10 healthy volunteers. Subject baseline plasma levels of MDA were 50 +/- 20 nM. After a meal of turkey meat cutlets, plasma MDA levels increased by 160 nM (P0.0001); after (B) there was a 75% reduction in the absorption of MDA (P0.0001). However, after (C), the elevation of plasma MDA was completely prevented (P0.0001). Similar results were obtained for MDA accumulation in urine. Our study suggests that red wine polyphenols exert a beneficial effect by the novel new function, absorption inhibition of the lipotoxin MDA. These findings explain the potentially harmful effects of oxidized fats found in foods and the important benefit of dietary polyphenols in the meal.

Summary The shelf life of fresh water prawns stored at 0°C was judged by a sensory panel and monitored by microbiological and chemical tests. After 14 days’ storage, but not after only 10 days, frozen (control sample) prawns were preferred over the former. During this period too, TVBN values of 0°C-stored prawn tails rose from 22 to 31 mg per 100 g, and TBA values rose from 0.25 to 0.65; the total aerobic psychrotrophic plate counts increased by about 2 logarithmic units. The relationship between the results of the various tests is discussed.

Summary The stability of carotenoids in paprika powders was studied at controlled humidity and temperatures during a period of eighty-five days. Reduction in colour intensity during storage at high temperature was rapid in powders with low (1%) moisture contents. Increasing the moisture contents to 14% enhanced colour stability and precluded pigment destruction. the ripening stage of the fruits from which the powder was processed also affected colour deterioration during storage. In powder stored under low moisture conditions produced from fruits allowed to dry on the plant for a considerable time, pigment deterioration was more rapid than in powder produced from fruits harvested ripe but still succulent.

The aim of this study was to evaluate the role of saliva in the oxidation process under the acidic condition of the stomach. Saliva specimens played varied roles in the lipid peroxidation process of heated muscle tissue in simulated gastric fluid: pro-oxidant effects, no effects, and antioxidant effects. To elucidate these differences, selected saliva components were examined. The pseudoperoxidase activity of lactoperoxidase increased lipid peroxidation, while thiocyanate and nitrite-reduced lipid peroxidation. The effect of a saliva specimen on lipid peroxidation was correlated with the concentration of nitrite in the specimen, but not with that of other saliva components. The inhibitory effect of nitrite may be due to its conversion to NO. Elucidation of the antioxidant effect of saliva on co-oxidation of d -α-tocopherol in gastric fluid, demonstrated that saliva alone cannot protect d -α-tocopherol from co-oxidation, although it partially protected against lipid peroxidation. The presence of red wine polyphenols in stomach medium totally inhibits food lipid peroxidation and d -α-tocopherol co-oxidation.

The Western diet contains large quantities of oxidized lipids, because a large proportion of the food in the diet is consumed in a fried, heated, processed, or stored form. We investigated the reaction that could occur in the acidic pH of the stomach and accelerate the generation of lipid hydroperoxides and cooxidation of dietary vitamins. To estimate the oxygen content in the stomach after food consumption, oxygen released from masticated bread (20 g) into deoxygenated water (100 mL) was measured. Under these conditions, the oxygen concentration rose by 250 microM and reached a full oxygen saturation. The present study demonstrated that heated red meat homogenized in human gastric fluid, at pH 3.0, generated hydroperoxides and malondialdehyde. The cross-reaction between free radicals produced during this reaction cooxidized vitamin E, beta-carotene, and vitamin C. Both lipid peroxidation and cooxidation of vitamin E and beta-carotene were inhibited at pH 3.0 by red wine polyphenols. Ascorbic acid (44 mg) at a concentration that represented the amount that could be ingested during a meal inhibited lipid peroxidation only slightly. Red wine polyphenols failed to prevent ascorbic acid oxidation significantly but, in conjunction with ascorbic acid, did inhibit lipid peroxidation. In the presence of catechin, a well-known polyphenol found in red wine, ascorbic acid at pH 3.0 works in a synergistic manner preventing lipid peroxidation and beta-carotene cooxidation. The present data may explain the major benefits to our health and the crucial role of consuming food products rich in dietary antioxidants such as fruits, vegetables, red wines, or green tea during the meal.

Our recent study demonstrated the potential of gastric fluid at pH 3.0 to accelerate lipid peroxidation and cooxidation of dietary constituents in the stomach medium. Metmyoglobin is known to catalyze the breakdown of lipid hydroperoxides to free radicals, a reaction that could enhance the propagation step and general lipid peroxidation. During this reaction, a part of the free radicals is autoreduced by metmyoglobin. At pH 3.0, metmyoglobin at low concentration was almost 7 x 10(4) times as effective as at pH 7.0 in enhancing the rate of lipid peroxidation. Our study demonstrated that metmyoglobin, at a low concentration (approximately 1:30), as compared with that of the hydroperoxides in the lipid system, worked prooxidatively increasing the amounts of linoleate hydroperoxides. However, at a high concentration (approximately 1:3), metmyoglobin acted antioxidatively and decomposed hydroperoxides, whose concentrations then remained at zero for a long time. Catechin, a known polyphenol, supports the inversion of metmyoglobin catalysis, from prooxidation to antioxidation. The antioxidative activity of the couple metmyoglobin-catechin was better at pH 3.0 than at pH 7.0, indicating that this reaction is more dependent on metmyoglobin than on catechin. During this reaction, catechin or quercetin not only donates reducing equivalents to prevent lipid peroxidation but also prevents the destruction and polymerization of metmyoglobin. The results of this research highlighted the important and possible reactions of heme proteins and polyphenols as couple antioxidants, working as hydroperoxidases or as pseudo-peroxidases. We hypothesize that the occurrence of these reactions in the stomach could have an important impact on our health and might help to better explain the health benefits of including foods rich in polyphenol antioxidants in the meal, especially when consuming red meat.

A number of natural phenolic compounds display antioxidant and cell protective effects in cell culture models, yet in some studies show prooxidant and cytotoxic effects. Pancreatic beta-cells have been reported to exhibit particular sensitivity to oxidative stress, a factor that may contribute to the impaired beta-cell function characteristic of diabetes. The aim of this study was to examine the potential of natural phenolics to protect cultured pancreatic beta-cells (betaTC1 and HIT) from H(2)O(2) oxidative stress. Exposure of cells to H(2)O(2) led to significant proliferation inhibition. Contrary to what one should expect, simultaneous exposure to H(2)O(2) and the phenolics, quercetin (10-100 microM), catechin (50-500 microM), or ascorbic acid (100-1000 microM), led to amplification of proliferation inhibition. At higher concentrations, these compounds inhibited proliferation, even in the absence of added H(2)O(2). This prooxidant effect is attributable to the generation of H(2)O(2) through interaction of the added phenolic compounds with as yet undefined componenets of the culture media. On the other hand, inclusion of metmyoglobin (30 microM) in the culture medium significantly reduced the prooxidant impact of the phenolics. Under these conditions, quercetin and catechin significantly protected the cells against oxidative stress when these components were present during the stress period. Furthermore, significant cell protection was observed upon preincubation of cells with chrysin, quercetin, catechin, or caffeic acid (50 microM, each) prior to application of oxidative stress. It is concluded that provided artifactual prooxidant effects are avoided, preincubation of beta-cells with relatively hydrophobic natural phenolics can confer protection against oxidative stress.

It has recently been suggested that the ability of apple extracts to inhibit proliferation of tumor cells in vitro may be due to phenolic/flavonoid antioxidants. Our study demonstrates that this inhibition is caused indirectly by H2O2 generated through interaction of the phenolics with the cell culture media. The results indicate that many previously reported effects of flavonoids and phenolic compounds on cultured cells may result from similar artifactual generation of oxidative stress. We suggest that in order to prevent such artifacts, the use of catalase and/or metmyoglobin in the presence of reducing agents should be considered as a method to decompose H2O2 and prevent generation of other reactive oxygen species, which could affect cell proliferation. The use of tumor cells and “nontumor cells” in a bioassay to measure antioxidant activity, in this context, is potentially misleading and should be applied with caution. Keywords: Apple; cell culture; H2O2; free iron; antioxidants; phenolics

Atherosclerosis may result partly from processes that occur following food consumption and that involve oxidized lipids in chylomicrons. We investigated reactions that could occur in the acidic pH of the stomach and accelerate the generation of lipid hydroperoxides and co-oxidation of dietary constituents. The ability of dietary polyphenols to invert catalysis from pro-oxidation to antioxidation was examined. The acidic pH of gastric fluid amplified lipid peroxidation catalyzed by metmyoglobin or iron ions. Metmyoglobin catalyzed peroxidation of edible oil, resulting in 8-fold increase of hydroperoxide concentration. The incubation of heated muscle tissue in simulated gastric fluid for 2 h enhanced hydroperoxides accumulation by 6-fold to 1200 microM. In the presence of catechin or red wine polyphenols, metmyoglobin catalyzed the breakdown of hydroperoxides to zero, totally preventing lipid peroxidation and beta-carotene cooxidation. We suggest that human gastric fluid may be an excellent medium for enhancing the oxidation of lipids and other dietary constituents. The results indicate the potentially harmful effects of oxidized fats intake in the presence of endogenous catalysts found in foods, and the major benefit of including in the meal plant dietary antioxidants.

The color of fresh meat is one of the most important quality criteria of raw muscle foods. This red color is principally due to the presence of oxymyoglobin. The present study was undertaken to examine the effect of a diet rich in polyunsaturated fatty acids (PUFA), the addition of NaCl, and the influence of dietary supplementation with vitamin E on calf muscle oxymyoglobin oxidation (color) and lipid peroxidation. Vitamin E was added to the feed at a concentration of 4000 mg/day for 90 days before slaughter. This diet increased the alpha-tocopherol concentration in muscle membrane from 2.6-2.8 to 6.5-7.0 microg/g of fresh weight. It was found that the diet rich in PUFA and, especially, the addition of NaCl increased muscle lipid peroxidation and oxymyoglobin oxidation as indicated by the contents of thiobarbituric acid-reactive substances and substances that impaired color value readings during storage at 4 degrees C. Both undesirable reactions during storage were controlled very efficiently by the presence of a critically high concentration of alpha-tocopherol in the muscle tissues. The findings concerning the antioxidant activity of alpha-tocopherol in this study form additional evidence of its efficient protection against oxidative reactions during storage of muscle tissues and its potential to maintain a high nutritional value in them.

Anthocyanins are one of the main classes of flavonoids in red wines, and they appear to contribute significantly to the powerful antioxidant properties of the flavonoids. In grapes and wines the anthocyanins are in the flavylium form. However, during digestion they may reach higher pH values, forming the carbinol pseudo-base, quinoidal-base, or the chalcone, and these compounds appear to be absorbed from the gut into the blood system. The antioxidant activity of these compounds, in several metal-catalyzed lipid oxidation model systems, was evaluated in comparison with other antioxidants. The pseudo-base and quinoidal-base malvidin 3-glucoside significantly inhibited the peroxidation of linoleate by myoglobin. Both compounds were found to work better than catechin, a well-known antioxidant. In a membrane lipid peroxidation system, the effectiveness of the antioxidant was dependent on the catalyst: In the presence of H(2)O(2)-activated myoglobin, the inhibition efficiency of the antioxidant was malvidin 3-glucoside > catechin > malvidin > resveratrol. However, in the presence of an iron redox cycle catalyzer, the order of effectiveness was resveratrol > malvidin 3-glucoside = malvidin > catechin. The pH-transformed forms of the anthocyanins remained effective antioxidants in these systems, and their I(50) values were between 0.5 and 6.2 microM.

A method for determining different types of reducing activity in aqueous leaf extracts of various edible herb species [watercress (Rorippa nasturtium-aquaticum), parsley (Petroselinum crispum), basil (Ocimum basilicum), and sage (Salvia officinalis L.)] was developed. This method, based on kinetics of the reduction of Fe(III) to Fe(II), was employed to study the correlation between leaf senescence rates under darkness and their relative reducing capacity in aqueous extracts, which represents an oxidative defense mechanism. Evidence is presented showing that the total reducing capacity is negatively correlated with the relative senescence rate of these four herb species and thereby provides a means to predict their storage potential. Also, the initiation of senescence processes was associated with a weakening of the oxidative defense systems. Exogenous application of active reducing agents (morin, ferulic acid, kaempferol, and glutathione) inhibited significantly chlorophyll degradation of detached parsley leaves to an extent related to their in vitro effectiveness of reducing activity. The results further emphasize the correlation between decreasing senescence rate and increasing reducing activity, thereby confirming the possible involvement of reducing compounds in oxidative defense systems of various edible senescing leaves.

Recent evidence for antitumor activity of carotenoids in humans has revived interest in these compounds in foods, nutrition, and medicine. A wide variation in carotenoid content was found among various Capsicum genotypes. The total carotenoid content was generally higher in C. annuum lines than in the accessions from other species. In contrast with the wide variation found in the content of the major carotenoids, the proportions of individual carotenoids within the total content and the ratios among them showed much less variation. The coefficients of variation for the ratios ranged from 8 to 35% in comparison with 70-90% for the carotenoid content. Significant correlations were found among the concentrations of the major carotenoids. Increasing the carotenoid concentration in high-pigment fruits of paprika by genetic manipulation improved not only the quality of the fruit as a source of food colorant but also its nutritive value. The breeding line 4126 contains about 240 mg of carotenoids/100 g of fresh weight, of which 20 mg is β-carotene

The antioxidant capability of coffee polyphenols to inhibit red-meat lipid peroxidation in stomach medium and absorption into blood of malondialdehyde (MDA) in humans was studied. Roasted-ground coffee polyphenols that were found to inhibit lipid peroxidation in stomach medium are 2- to 5-fold more efficient antioxidant than those found in instant coffee. Human plasma from ten volunteers analyzed after a meal of red-meat cutlets (250 g) revealed a rapid accumulation of MDA. The accumulation of MDA in human plasma modified low-density lipoprotein is known to trigger atherogenesis. Consumption of 200 mL roasted coffee by ten volunteers during a meal of red-meat cutlets, resulted after 2 and 4 h in the inhibition by 80 and 50%, respectively, of postprandial plasma MDA absorption. The results obtained in vitro simulated stomach model on MDA accumulation were predictive for the amount of MDA absorbed into circulating human plasma, in vivo. Timing the consumption of coffee during the meals may make it a very active functional food.

Correlation studies between leaf senescence rates of three edible herb species, watercress (Rorippa nasturtium-aquaticum), parsley (Petroselinum crispum), and sage (Salvia officinalis L.), and their oxidative defense systems were conducted with detached leaves under simulated shelf-life storage conditions. The relative order of leaf senescence rate, based on their rate of chlorophyll (Chl) degradation and malondialdehyde accumulation, was watercress>parsley>sage. However, all three herb species showed high proteolysis rates from the first day of incubation. Of five oxidative defense systems examined in the three herb species, only the system of total reducing capacity correlated well with their relative order of Chl degradation and could therefore predict their storage potential

Antioxidants have been difficult to evaluate in oils and food emulsions due in part to the complex interfacial phenomena involved. Lipophilic and hydrophilic antioxidants were evaluated with corn oil stripped of natural tocopherols in bulk and in emulsion systems. Oridation was followed by determining formation of hydroperoxides and hexanal. The lipophilic antioxidants α-tocopherol and ascorbyl palmitate were more effective in an oil-in-water emulsion system than in bulk oil, while the opposite trend was found for the hydrophilic antioxidants Trolox and ascorbic acid. The oil-insoluble ascorbic acid was a particularly efficient antioxidant in suspension in the bulk oil system

The concentrations of phenolics of three grape varieties and two red wines were determined. The red grape variety and the red wines contain phenolics at concentrations of 920 mg/kg and 1800 and 3200 mg/L, respectively. The antioxidative effects of wine phenolics on the catalysis of lipid peroxidation by biological catalysts such as myoglobin, cytochrome c, iron ascorbate, and copper ions were estimated. Lipid peroxidation catalyzed by myoglobin, cytochrome c, and iron ascorbate was inhibited (I 50 ) by wine phenolics at concentrations of 0.2, 0.35, and 0.9 μg of phenolics/mL

Objective Lipophilic polyphenols in fruit beverages can avidly bind to surfaces of microorganisms and to blood cells and to impart upon them enhanced oxidant scavenging abilities (OSA). However, since many of the polyphenols are actually not fully soluble in water, they are therefore not available to act as effective antioxidant agents. We hypothesized that whole saliva, proteins such as albumin and mucin, human red blood cells and platelets, may all increase the “solubility” and availability of lipophilic antioxidant polyphenols thus increasing the OSA of whole saliva. Design The OSA of whole un-stimulated human saliva, obtained from healthy donors and of combinations among saliva, mucin, blood cells, fruit beverages and reagent polyphenols were quantified by chemiluminescence, DPPH radical and tetrazolium reduction assays. Kinetics of the clearance of polyphenols from saliva after holding in the mouth for 30 s of an extract from beverages cinnamon was assayed by the Folin Ciocalteu's and the luminescence assays. Results OSA of fruit beverages and of reagent polyphenols were markedly increased by whole saliva, mucin and by red blood cells. Polyphenols associated with a cinnamon extract were retained in the oral cavity for several hours as measured by luminescence and Folin reagent techniques. Conclusions A new approach to explain the additional role of saliva and salivary proteins and of blood cells as enhancers of OSA of lipophilic polyphenols is presented. This might have a significant importance to assess complex interactions among polyphenols from nutrients, salivary antioxidants, salivary proteins and blood cells extravasated from injure capillaries during infection and inflammation.

The present study demonstrated that nitric oxide, which is an important mammalian metabolite, can inhibit oxidation by lipoxygenase, cyclooxygenase and hemoglobin. The inhibition is manifested as a lag-phase that is reversible. The inhibitory effect of nitric oxide on lipoxygenase and cyclooxygenase seems to derive from i) the capability of .NO to reduce the ferric enzyme to the ferrous form, which is inactive; ii) competition for the iron site available for exogenous ligands; and iii) the radical scavenging ability of the nitroxide radical. Nitric oxide may act as a modulator of the arachidonic acid cascade and in the generation of oxygen-active species.

Salivary nitrite plays a role in the lipid peroxidation process of muscle tissue in simulated gastric fluid. The objectives of our study were to elucidate the fate of nitrite in the presence of reducing compounds and to evaluate its effect on lipid peroxidation during digestion. Nitrite at pH 3 (possibly NO2 , not NO ) can oxidize β-carotene, but the addition of reducing compounds, ascorbic acid or polyphenols, alters its effect. Ascorbic acid alone promoted the formation of NO from nitrite only up to pH 3, but the addition of iron ions facilitated the formation of NO up to pH 5.5. NO prevented membranal lipid peroxidation under stomach conditions. Nitrite, only in the presence of reducing compounds, achieved the same goal but at much higher concentrations. Addition of polyphenols to nitrite synergistically improved its antioxidant effect. Therefore, to promote NO production and to achieve better control of the lipid peroxidation process in the stomach, a nitrite-rich meal should be consumed simultaneously with food rich in polyphenols.

The prooxydant effect of NaCl on minced turkey muscle lipid peroxidation was demonstrated by using 2 methods that determine accumulation of TBA-Rs and conjugated dienes. The prooxydant effect of NaCl was inhibited by EDTA and ceruleoplasmin

The study was conducted to evaluate the effect of the cytosolic extract (soluble fraction) on lipid peroxidation of the water-extracted muscle residue (insoluble fraction) stimulated by H 2 O 2 -activated myoglobin and iron ion dependent enzymatic and non enzymatic reactions

Food is an essential to our existence but under certain conditions it could become the origin to the accumulative health damages. Technological processes as heating, chopping, mincing, grounding, promote the lipid oxidation process in muscle tissues and meat foodstuffs. Lipid oxidation occurred rapidly in turkey muscle, intermediate in duck, and slowest in chicken during frozen storage. Depletion of tocopherol during frozen storage was more rapid in turkey and duck compared to chicken. These processes developed from lipid peroxides produce many cytotoxic compounds including malondialdehyde (MDA). The muscle tissue is further oxidized in stomach conditions producing additional cytotoxic compounds. Oxidized lipids that are formed during digestion of a meal possess the potential to promote reactions that incur vascular diseases. A grape seed extract (1% of the meat weight) and butylated hydroxytoluene (0.2% of the lipid weight) were each effective at preventing formation of lipid oxidation products for 3 hours during co-incubation with cooked turkey meat in simulated gastric fluid (SGF). Polyphenols in the human diet, as an integral part of the meal prevent the generation and absorption of cytotoxic compounds and the destruction of essential nutrients, eg. antioxidants vitamins during the meal. Polyphenols act as antioxidants in the gastrointestinal tract; they scavenge free radicals and may interact with reactive carbonyls, enzymes and proteins. These all reactions results in decreasing the absorption of reactive carbonyls and possible other cytotoxic compounds into the plasma. Consumptions of diet high in fat and red meat are contributory risk factors partly due to an increase production of cytotoxic oxidized lipid products eg. MDA. However, the simultaneously consumption of polyphenols rich foods reduce these factors. Locating the biological site of action of polyphenols in the in the gastrointestinal tract may explain the paradox between the protective effect of a highly polyphenols rich diet and the low bioavailability of these molecules in human plasma. It may also explain the "French paradox" and the beneficial effect of Mediterranean and Japanese diets, in which food products with high antioxidants content such as polyphenols are consumed during the meal.

To determine the stomach bioreactor capability for food oxidation or antioxidation, rats were fed red turkey meat cutlets (meal A) or red turkey meat cutlets and red wine concentrate (meal B). The hydroperoxides (LOOH) and malondialdehyde (MDA) levels of the stomach contents were evaluated during and after digestion; the postprandial plasma MDA level was also evaluated. In independently fed rats, the stomach LOOH concentration fell substantially 90 min following the meal, and the addition of red wine polyphenols enhanced LOOH reduction 3-fold. A similar trend was obtained for MDA. After pyloric ligation, the stomach contents of rats fed red meat homogenate showed >2-fold increases in LOOH and MDA accumulation. The postprandial plasma MDA level increased significantly by 50% following meal A and was maintained or even fell by 34% below basal level following meal B. The findings show that consumption of partially oxidized food could increase lipid peroxidation in the stomach and the absorption of cytotoxic lipid peroxidation products into the body. The addition of antioxidants such as red wine polyphenols to the meal may alter these outcomes. These findings explain the potentially harmful effects of oxidized fats in foods and the important benefit of consuming dietary polyphenols during the meal.

The main object of this study was to evaluate the effect of removing the iron supplement from the diet fed prior to slaughtering on the stability of turkey muscle tissue stored at 5°C. The results demonstrate that a decrease in nutrititional Fe 3-7 weeks prior to slaughtering could result in a reduction of more than 50% in lipid peroxidation in in situ turkey dark muscle. Turkey light muscle, which is by its nature more stable to lipid peroxidation, was affected

A method of separating and identifying unsaponified pigments extracted from paprika (Capsicum annuum L. var. Lehava) is described. It is based on high-pressure liquid chromatography (two serially connected C 18 columns with an empirical gradient) coupled with a photodiode array detection method. Well-separated groups of peaks, corresponding to free and mono- and diesterified carotenoids and β-carotene was observed. The relative changes of these various groups during saponification were monitorable owing to slow transesterification by sodium methoxide at room temperature

Oxymyoglobin is the main pigment in muscle tissues, responsible for the bright red color of fresh meat. Oxidation of the heme iron from the ferrous to the ferric metmyoglobin produces the brownish color that consumers find undesirable in fresh meat. The aim of this study was to elucidate the mechanism of oxymyoglobin oxidation in muscle tissues by using a model system containing oxymyoglobin and muscle membranes oxidized by an iron redox cycle. Oxidation of oxymyoglobin was determined from the decrease in absorption of the solution measured by a spectrophotometer at 582 nm. Lipid peroxidation was determined by accumulation of TBARS and conjugated dienes. The higher rates of oxidation of oxymyoglobin (20 microM) and lipid oxidation were achieved by using ferric iron and ascorbic acid at concentrations of 50 and 200 microM, respectively. Increasing the concentration of ascorbic acid to 2000 microM switched its effect to antioxidative. Increasing the concentration of oxymyoglobin from 20 to 80 microM inhibited lipid peroxidation by >90% and partially prevented oxymyoglobin oxidation.

Antioxidant nutrients from fruits and vegetables are believed to be a class of compounds that exert their effects in humans by preventing oxidative processes which contribute to the onset of several degenerative diseases. This study found a new class of dietary cationized antioxidants in red beets (Beta vulgaris L.). These antioxidants are betalains, and the major one, betanin, is a betanidin 5-O-beta-glucoside. Linoleate peroxidation by cytochrome c was inhibited by betanin, betanidin, catechin, and alpha-tocopherol with IC(50) values of 0.4, 0.8, 1.2, and 5 microM, respectively. In addition, a relatively low concentration of betanin was found to inhibit lipid peroxidation of membranes or linoleate emulsion catalyzed by the "free iron" redox cycle, H(2)O(2)-activated metmyoglobin, or lipoxygenase. The IC(50) inhibition of H(2)O(2)-activated metmyoglobin catalysis of low-density lipoprotein oxidation by betanin was

Ferritins from horse spleen (Sigma Chemical Co.) and those obtained from turkey liver and dark and light muscles were separated by gel chromatography and SDS gel electrophoresis. The results indicated that the basic subunits of 20 000-22 000 Da are similar between the ferritins extracted from liver or turkey muscles. The amount of iron/ferritin molecules in muscles is very low, only approximately 5% of that in the liver. Dark and light muscles during storage at 4 degrees C released iron from ferritin. Ferritin extracted from turkey muscles stimulated muscle membrane lipid peroxidation. It seems that ferritin plays an important role in the process of muscle lipid peroxidation by being one of the main sources for "free" iron for this reaction.

Publisher Summary This chapter discusses the nitric oxide (NO) and metal-catalyzed reactions. The main biological functions of NO. include the stimulation of the soluble guanylate cyclase and elevation of cyclic guanosine monophosphate (cGMP) in various cells. NO activates soluble guanylate cyclase through an interaction with iron in the heme of the enzyme. NO can undergo numerous reactions; it can act as either a weak oxidizing compound or as a reducing agent, forming NO+ (nitrosonium cation) or NO– (nitroxyl anion). Some of the complexes are diamagnetic and others paramagnetic, which can be detected by electron paramagnetic resonance (EPR). Paramagnetic species are formed from the reaction of NO with ferrous ion in aqueous solution containing one or more additional coordinating anionic ligands. Application of the methods described in the chapter enables to determine the antioxidative effects imposed by NO. on ferrous complexes. The overall effects of NO. as activator, modulator, or inhibitor seem to be dictated by its site of biosynthesis, its concentration, and the presence and concentration of transition metals.

Several grape varieties and red wines were found to contain large concentration of phenolic compounds which work as antioxidant in-vitro and in-vivo. Wastes from wine production contain antioxidants in large amounts, between 2-6% on dry material basis. Red wines but also white wines were found to prevent lipid peroxidation of turkey muscle tissues stored at 5oC. The antioxidant reaction of flavonoids found in red wines against lipid peroxidation were found to depend on the structure of the molecule. Red wine flavonoids containing an orthodihydroxy structure around the B ring were found highly active against LDL and membrane lipid peroxidation. The antioxidant activity of red wine polyphenols were also found to be dependent on the catalyzer used. In the presence of H2O2-activated myoglobin, the inhibition efficiency was malvidin 3-glucoside>catechin>malvidin>resveratol. However, in the presence of an iron redox cycle catalyzer, the order of effectiveness was resveratol>malvidin 3-glucoside = malvidin>catechin. Differences in protein binding were found to affect antioxidant activity in inhibiting LDL oxidation. A model protein such as BSA, was investigated on the antioxidant activity of phenolic compounds, grape extracts, and red wines in a lecithin-liposome model system. Ferulic acid followed by malvidin and rutin were the most efficient in inhibiting both lipid and protein oxidation. Catechin, a flavonal found in red-wines in relatively high concentration was found to inhibit myoglobin catalyzed linoleate membrane lipid peroxidation at a relatively very low concentration. This effect was studied by the determination of the by-products generated from linoleate during oxidation. The study showed that hydroperoxides are catalytically broken down, not to an alcohol but most probably to a non-radical adduct. The ability of wine-phenolics to reduce iron and from complexes with metals were also demonstrated. Low concentration of wine phenolics were found to inhibit lipoxygenase type II activity. An attempt to understand the bioavailability in humans of antocyanins from red wine showed that two antocyanins from red wine were found unchanged in human urine. Other antocyanins seems to undergo molecular modification. In hypercholesterolemic hamsters, aortic lipid deposition was significantly less in animals fed diets supplemented with either catechin or vitamin E. The rate of LDL accumulation in the carotid arteries was also significantly lower in the catechin and vitamin E animal groups. These results suggested a novel mechanism by which wine phenolics are associated with decreased risk of coronary heart diseases. This study proves in part our hypothesis that the "French Paradox" could be explained by the action of the antioxidant effects of phenolic compounds found at high concentration in red wines. The results of this study argue that it is in the interest of public health to increase the consumption of dietary plant falvonoids. Our results and these from others, show that the consumption of red wine or plant derived polyphenolics can change the antioxidant tone of animal and human plasma and its isolated components towards oxidative reactions. However, we need more research to better understand bioavailability and the mechanism of how polyphenolics affect health and disease.