Lycopene and Its Antioxidant Role in the Prevention of Cardiovascular Diseases-A Critical Review.

The present review is based mainly on papers published between 2000 and 2011 and gives information about the properties of the carotenoid lycopene in chemical and biological systems and its possible role in preventing cardiovascular diseases (CVD). The main aim of this report is to highlight its role as an antioxidant, also reported are bioactive properties that may influence the development of foam cells and protection against endothelial cell damage. The paper will also examine recent observations that lycopene may improve blood flow and reduce inflammatory responses. Lycopene possesses antioxidant properties in vitro, and some epidemiological studies have reported protective effects against the progression of CVD. The oxidation of human low density lipoproteins (LDL) is a fundamental mechanism in the initiation of atherosclerosis. A beneficial role of lycopene as antioxidant in the prevention of CVD is suggested but the data are still controversial. Lycopene is believed to be the most potent carotenoid antioxidant in vitro. Tissue culture experiments and animal studies support potential cardioprotective effects for lycopene and other carotenoids in the blood. Most studies showed beneficial effects of lycopene to individuals who are antioxidant-deficient like elderly patients, or humans exposed to higher levels of oxidative stress like smokers, diabetics, hemodialysis patients and acute myocardial infarction patients. By defining the right population and combining antioxidant potentials of lycopene with vitamins and other bioactive plant compounds, the beneficial role of lycopene in CVD can be clarified in future studies.

A Review About Lycopene-Induced Nuclear Hormone Receptor Signalling in Inflammation and Lipid Metabolism via still Unknown Endogenous Apo-10´-Lycopenoids.

Lycopene is the red pigment in tomatoes and tomato products and is an important dietary carotenoid found in the human organism. Lycopene-isomers, oxidative lycopene metabolites and apo-lycopenoids are found in the food matrix. Lycopene intake derived from tomato consumption is associated with alteration of lipid metabolism and a lower incidence of cardiovascular diseases (CVD). Lycopene is mainly described as a potent antioxidant but novel studies are shifting towards its metabolites and their capacity to mediate nuclear receptor signalling. Di-/tetra-hydro-derivatives of apo-10´-lycopenoic acid and apo-15´-lycopenoic acids are potential novel endogenous mammalian lycopene metabolites which may act as ligands for nuclear hormone mediated activation and signalling. In this review, we postulate that complex lycopene metabolism results in various lycopene metabolites which have the ability to mediate transactivation of various nuclear hormone receptors like RARs, RXRs and PPARs. A new mechanistic explanation of how tomato consumption could positively modulate inflammation and lipid metabolism is discussed.

Intestinal scavenger receptors are involved in vitamin K1 absorption.

Vitamin K1 (phylloquinone) intestinal absorption is thought to be mediated by a carrier protein that still remains to be identified. Apical transport of vitamin K1 was examined using Caco-2 TC-7 cell monolayers as a model of human intestinal epithelium and in transfected HEK cells. Phylloquinone uptake was then measured ex vivo using mouse intestinal explants. Finally, vitamin K1 absorption was compared between wild-type mice and mice overexpressing scavenger receptor class B type I (SR-BI) in the intestine and mice deficient in cluster determinant 36 (CD36). Phylloquinone uptake by Caco-2 cells was saturable and was significantly impaired by co-incubation with α-tocopherol (and vice versa). Anti-human SR-BI antibodies and BLT1 (a chemical inhibitor of lipid transport via SR-BI) blocked up to 85% of vitamin K1 uptake. BLT1 also decreased phylloquinone apical efflux by ∼80%. Transfection of HEK cells with SR-BI and CD36 significantly enhanced vitamin K1 uptake, which was subsequently decreased by the addition of BLT1 or sulfo-N-succinimidyl oleate (CD36 inhibitor), respectively. Similar results were obtained in mouse intestinal explants. In vivo, the phylloquinone postprandial response was significantly higher, and the proximal intestine mucosa phylloquinone content 4 h after gavage was increased in mice overexpressing SR-BI compared with controls. Phylloquinone postprandial response was also significantly increased in CD36-deficient mice compared with wild-type mice, but their vitamin K1 intestinal content remained unchanged. Overall, the present data demonstrate for the first time that intestinal scavenger receptors participate in the absorption of dietary phylloquinone.

Vitamin deficiencies in humans: can plant science help?

The term vitamin describes a small group of organic compounds that are absolutely required in the human diet. Although for the most part, dependency criteria are met in developed countries through balanced diets, this is not the case for the five billion people in developing countries who depend predominantly on a single staple crop for survival. Thus, providing a more balanced vitamin intake from high-quality food remains one of the grandest challenges for global human nutrition in the coming decade(s). Here, we describe the known importance of vitamins in human health and current knowledge on their metabolism in plants. Deficits in developing countries are a combined consequence of a paucity of specific vitamins in major food staple crops, losses during crop processing, and/or overreliance on a single species as a primary food source. We discuss the role that plant science can play in addressing this problem and review successful engineering of vitamin pathways. We conclude that while considerable advances have been made in understanding vitamin metabolic pathways in plants, more cross-disciplinary approaches must be adopted to provide adequate levels of all vitamins in the major staple crops to eradicate vitamin deficiencies from the global population.

Stability of bacterial carotenoids in the presence of iron in a model of the gastric compartment - comparison with dietary reference carotenoids.

Recently isolated spore-forming pigmented marine bacteria, Bacillus indicus HU36 and Bacillus firmus GB1 are sources of carotenoids (∼fifteen distinct yellow and orange pigments and ∼thirteen distinct pink pigments, respectively). They are glycosides of oxygenated lycopene derivatives (apo-lycopenoids) and are assumed to be more heat- and gastric-stable than common carotenoids. In this study, the oxidation by O2 of the bacterial carotenoids was initiated by free iron (Fe(II) and Fe(III)) or by heme iron (metmyoglobin) in a mildly acidic aqueous solution mimicking the gastro-intestinal compartment and compared to the oxidation of the common dietary carotenoids ß-carotene, lycopene and astaxanthin. Under these conditions, all bacterial carotenoids appear more stable in the presence of heme iron vs. free iron. Carotenoid autoxidation initiated by Fe(II) is relatively fast and likely involves reactive oxygen-iron species derived from Fe(II) and O2. By contrast, the corresponding reaction with Fe(III) is kinetically blocked by the slow preliminary reduction of Fe(III) into Fe(II) by the carotenoids. The stability of carotenoids toward autoxidation increases as follows: ß-carotene

Interactions between Carotenoids from Marine Bacteria and Other Micronutrients: Impact on Stability and Antioxidant Activity.

Recently isolated spore-forming pigmented marine bacteria Bacillus indicus HU36 are sources of oxygenated carotenoids with original structures (about fifteen distinct yellow and orange pigments with acylated d-glucosyl groups). In this study, we evaluated the stability (sensitivity to iron-induced autoxidation) and antioxidant activity (inhibition of iron-induced lipid peroxidation) of combinations of bacterial HU36 carotenoids with the bacterial vitamin menaquinone MQ-7 and with phenolic antioxidants (vitamin E, chlorogenic acid, rutin). Unexpectedly, MQ-7 strongly improves the ability of HU36 carotenoids to inhibit Fe(II)-induced lipid peroxidation, although MQ-7 was not consumed in the medium. We propose that their interaction modifies the carotenoid antioxidant mechanism(s), possibly by allowing carotenoids to scavenge the initiating radicals. For comparison, ß-carotene and lycopene in combination were shown to exhibit a slightly higher stability toward iron-induced autoxidation, as well as an additive antioxidant activity as compared to the carotenoids, individually. HU36 carotenoids and phenolic antioxidants displayed synergistic activities in the inhibition of linoleic acid peroxidation induced by heme iron, but not by free iron. Synergism could arise from antioxidants interacting via electron transfer through the porphyrin nucleus of heme iron. Overall, combining antioxidants acting via complementary mechanisms could be the key for optimizing the activity of this bacterial carotenoid cocktail.

Impact of onions in tomato-based sauces on isomerization and bioaccessibility of colorless carotenes: phytoene and phytofluene.

Onions as an interesting ingredient have been proved to promote Z-isomerization of lycopene and increase bioaccessibility of total-lycopene. Phytoene (PT) and phytofluene (PTF), the precursors of lycopene, are colorless carotenes, which are attracting much attention and are also abundant in tomatoes. Therefore, onions might also affect the distribution and bioaccessibility of PT and PTF isomers during heating tomato (hot-break and cold-break purees)-onion-extra virgin olive oil (EVOO) sauces. The addition of onions (or diallyl disulfide present in onions) into tomato purees did not cause degradation of PT or PTF; however it favored E/Z-isomerization of PT and PTF by reducing the proportions of their natural Z-isomers (Z-15-PT and Z2,3-PTF) and decreased the bioaccessibility of total-PT and total-PTF. Simultaneously, a complex picture was obtained for the effect of onions on the bioaccessibility of individual PT and PTF isomers, depending on the precise isomer. Bioaccessibility of PT and PTF isomers in tomato-based sauces decreased in the order: 15-Z-PT > all-E-PT; Z2,3-PTF > all-E-PTF > Z4 or Z5-PTF; total-PT > total-PTF. E-isomerization of PT and PTF enhanced by onions during heating tomato-onion purees decreased their bioaccessibility.

Mechanisms Governing the Transfer of Pure and Plant Matrix Carotenoids Toward Emulsified Triglycerides.

SCOPE: The study aims to assess the role of factors assumed to be involved in the transfer of carotenoids from plant matrices to dietary emulsions in the upper digestive tract. METHODS AND RESULTS: Transfer is first measured as a function of time of pure ß-carotene (ßC), lutein (LUT), and lycopene (LYC) to triglyceride (TG) droplets dispersed in water. Then the transfer to TG droplets stabilized with either bovine serum albumin (BSA), phospholipids (PL), or both is measured. Finally, transfer of tomato and spinach puree carotenoids to these emulsions is measured. The maximal transfer efficiency of the pure carotenoids to uncoated emulsions is very efficient, ranging from 59% to 77%. However, it is dramatically impaired, ranging from 0.5% to 31% (p < 0.05), when emulsions are stabilized by the emulsifiers. Conversely, when LUT, and to a less extent ßC, but not LYC, is provided by the vegetable purees, its maximal transfer efficiency is significantly higher for the coated emulsions than for the uncoated one. CONCLUSIONS: Emulsifiers can dramatically impair the transfer of pure carotenoids to emulsion TG while they can facilitate the transfer of carotenoids from plant matrices. This suggests that specific interactions between plant matrix compounds and emulsifiers can enhance the transfer efficiency of carotenoids.

Food Structure Modulates the Bioavailability of Triglycerides and Vitamin D, and Partly That of Lutein: A Randomized Trial with a Crossover Design in Adults.

SCOPE: The specific effect of the food matrix structure on fat-soluble micronutrient bioavailability is only partly understood. Evaluating fat-soluble micronutrient bioavailability after consumption of foods displaying similar composition but different structure is aimed at. METHODS AND RESULTS: Twelve healthy subjects are enrolled in a randomized, open label, crossover postprandial trial. Four different model foods are tested: custard, pudding, sponge cake, and biscuit. Vitamin D3 , lutein, and triglyceride chylomicron responses, evaluated as postprandial areas under the curve, are then assayed. Custard triglyceride response is higher than pudding and biscuit responses (up to +122.7%, p < 0.0001). Sponge cake vitamin D3 response is higher than biscuit response (+26.6%, p = 0.047). No difference between the model foods are observed regarding lutein responses. Triglyceride responses peak at 3 h for all conditions, while vitamin D3 and lutein peaks are delayed by 1 h with the biscuit matrix compared to other model foods. CONCLUSION: Food structure can significantly impact on triglyceride and vitamin D3 bioavailability in terms of absorbed amounts and/or maximum absorption time. The data highlight positive correlations between triglyceride, vitamin D, and lutein nutrient responses. These results are of particular interest to develop functional foods for population subgroups such as the elderly.

Heating tomato puree in the presence of lipids and onion: The impact of onion on lycopene isomerization.

Z-lycopene isomers are more bioavailable than all-E-lycopene, especially 5-Z-lycopene. Based on our observations, the addition of unblanched onion could favor Z-isomerization of lycopene (by more than 94%) during heating tomato-onion-extra virgin olive oil (EVOO) purees at 90 °C for 2 h. The increase in Z-lycopene was correlated linearly with the addition of unblanched onion, with R2 > 0.92, and increased rates of 5-Z-lycopene were 3-4 times higher than for 9-Z-lycopene and 13-Z-lycopene. Diallyl disulfide (DADS), formed by alliinase-catalyzed breakdown of non-volatile precursors in onion, contributed to these increases and correlated linearly (R2 > 0.79, 0-0.50 mg/g puree) with increased Z-lycopene. Increased rates of 5-Z-lycopene were also 3-4 times higher than for 9-Z-lycopene and 13-Z-lycopene. However, blanching of onion, in tomato-onion-EVOO purees, before heating, significantly decreased the effect of onion on Z-isomerization of lycopene.

A D-optimal mixture design of tomato-based sauce formulations: effects of onion and EVOO on lycopene isomerization and bioaccessibility.

A D-optimal mixture design was used to study the effects of onion and extra virgin olive oil (EVOO) on lycopene Z-isomerization, lycopene diffusion into oil (expressed as a partition factor between tomato-based puree and oil) and in vitro bioaccessibility of lycopene isomers after thermal treatment of tomato-based puree consisting of tomato (75-100%), onion (0-20%) and EVOO (0-5%). A decrease of tomato puree could improve lycopene Z-isomerization, lycopene diffusion and lycopene bioaccessibility. The component interactions had an important influence on the Z-isomerization of lycopene, besides the linear mixtures of components. However, only linear mixtures of components appeared to have significant effects on the diffusion and bioaccessibility of lycopene, in which EVOO had the highest positive effect followed by onion. The bioaccessibility of lycopene isomers in every tomato-based sauce formulation decreased in the order: 13-Z-lycopene > 9-Z-lycopene > 5-Z-lycopene > all-E-lycopene. The bioaccessibility of total-Z-lycopene was at least 10 times higher than that of all-E-lycopene. Proportions of total-Z-lycopene were correlated positively with the partition factor and bioaccessibility of total-lycopene, with an r over 0.730 (p = 0.0031). Therefore, increased Z-lycopene proportions probably contributed to enhanced lycopene diffusion and bioaccessibility. The positive effects of components, especially onion, on total-lycopene diffusion and bioaccessibility were probably because the components increased the Z-isomerization of lycopene during heating of tomato-based puree.

The Effect of an Iron Supplement on Lycopene Metabolism and Absorption During Digestion in Healthy Humans.

SCOPE: To investigate the formation and absorption of lycopene (LYC) metabolites in the human upper gastrointestinal lumen, in the absence and presence of iron. METHODS: Healthy males (n = 7) consumed test meals that deliver ≈22 mg LYC + ≈0.3 mg apo-lycopenals from oleoresin without (-FeSO4 ) and with ferrous sulfate (160 mg, +FeSO4 ). Subjects were intubated with a naso-gastric/naso-duodenal tube. Digesta, blood plasma, and the triglyceride-rich lipoprotein (TRL) fractions of plasma were analyzed using LC-MS/MS, to measure LYC and apo-lycopenoids. RESULTS: Digesta LYC concentrations increased with time (p = 1.2 × 10-7 ), decrease with time × iron (p = 1.1 × 10-5 ), and remain ≈200× higher than apo-lycopenals/lycopenone. Digesta apo-8'-, -10'-, -12'-, -14'-, -15-lycopenal, and apo-13-lycopenone concentrations increased with time (p < 0.01), apo-12'-, -14'-, -15-lycopenal, apo-13-lycopenone increase with iron (p < 0.05), and time × iron decrease apo-8'-, -10'-, -12'-, -14'-, -15-lycopenal, apo-13-lycopenone concentrations (p < 0.01). A 1.9-fold decrease in LYC TRL area-under-the-time-concentration-curve is observed after the test meal +FeSO4 versus the test meal -FeSO4 (p = 0.02). Apo-lycopenals were detected in later TRL fractions, and no apo-lycopenols or apo-lycopenoic acids were observed in any samples. CONCLUSIONS: FeSO4 reduces LYC absorption. Apo-lycopenals appear to be absorbed from foods, and not made in significant quantities during digestion.

Increased diffusivity of lycopene in hot break vs. cold break purees may be due to bioconversion of associated phospholipids rather than differential destruction of fruit tissues or cell structures.

Lycopene bioaccessibility is enhanced by processing, as explained by the destructuration of plant tissues, making diffusion easier. However, in tomato, the relationship between grinding intensity and lycopene release from purees suffers from uncertainty. In particular, hot break puree exhibited twice as much diffusible lycopene as compared to cold break, while both were processed with the same grinding intensity. To explain the difference, we systematically studied the diffusivity of particles according to their size and integrity, and used microscopic and physical analyses to reveal structural differences. Neither particle size distribution, nor cell destruction, nor plastid transformation exhibited any correlation to the differences in diffusivity. However, Raman microspectroscopy combined with a chemometric analysis revealed significant changes in lycopene spectra and a putative linkage to phospholipid transformation. Phospholipid profiling of five pairs of contrasted purees revealed that, during the cold break, a transition from complex phospholipids to more simple phosphatidic acid molecules systematically occurred.

How does tomato quality (sugar, acid, and nutritional quality) vary with ripening stage, temperature, and irradiance?

The objective of this study was to understand the respective impact of ripening stage, temperature, and irradiance on seasonal variations of tomato fruit quality. During ripening, concentrations in reducing sugars, carotenes, ascorbate, rutin, and caffeic acid derivates increased, whereas those in titratable acidity, chlorophylls, and chlorogenic acid content decreased. Fruit temperature and irradiance affected final fruit composition. Sugars and acids (linked to fruit gustative quality) were not considerably modified, but secondary metabolites with antioxidant properties were very sensitive to fruit environment. Increased fruit irradiance enhanced ascorbate, lycopene, beta-carotene, rutin, and caffeic acid derivate concentrations and the disappearance of oxidized ascorbate and chlorophylls. Increasing the temperature from 21 to 26 degrees C reduced total carotene content without affecting lycopene content. A further temperature increase from 27 to 32 degrees C reduced ascorbate, lycopene, and its precursor's content, but enhanced rutin, caffeic acid derivates, and glucoside contents. The regulation by light and temperature of the biosynthesis pathways of secondary metabolites is discussed.

Production, separation, and characterization of apo-luteinoids by LC-MS/MS.

It has been postulated that chemical or enzymatic catabolism of carotenoids could produce apo­carotenoids which have biological activity. Our objective was to generate and chemically characterize a series of apo­luteinoids (i.e. products resulting from the catabolism of lutein) which could putatively be found in vivo. Lutein was oxidized using potassium permanganate to produce a series of apo­luteinals/luteinone of subsequently shorter chain lengths, from apo­8'­luteinal to apo­11­luteinal. Sodium borohydride reduced this mixture into the corresponding alcohols (i.e. apo­luteinols). Similarly, Tollens' reagent was employed to oxidize the aldehyde series into carboxylic acids (i.e. apo­luteinoic acids). Mixtures of products were separated via HPLC and characterized in-line using photodiode array (PDA) and tandem mass spectrometry (MS-MS). A global HPLC-PDA-MS/MS method was developed to separate the products, and application of the methods to the symmetric xanthophyll zeaxanthin further confirmed the ε- and ß-ring species. These methods can be employed for the study of lutein oxidation products in plants, foods and biological samples.

Carotenoids: Experimental Ionization Energies and Capacity at Inhibiting Lipid Peroxidation in a Chemical Model of Dietary Oxidative Stress.

Carotenoids are important natural pigments and micronutrients contributing to health prevention by several mechanisms, including their electron-donating (antioxidant) activity. In this work, a large series of carotenoids, including 11 carotenes and 14 xanthophylls, have been investigated by wavelength-resolved atmospheric pressure photoionization mass spectrometry (DISCO line of SOLEIL synchrotron), thus allowing the experimental determination of their ionization energy (IE) for the first time. On the other hand, the carotenoids have been also investigated for their ability to inhibit the heme iron-induced peroxidation of linoleic acid in mildly acidic micelles, a simple but relevant chemical model of oxidative stress in the gastric compartment. Thus, the carotenoids can be easily classified from IC50 concentrations deduced from the time dependence of the lipid hydroperoxide concentration. With a selection of two carotenes and three xanthophylls a quantitative analysis is also provided to extract stoichio-kinetic parameters. The influence of the carotenoid structure (number of conjugated carbon-carbon double bonds, presence of terminal six-membered rings, hydroxyl, keto, and/or epoxy groups) on the IE, IC50, and stoichio-kinetic parameters is discussed in details. The data show that the antioxidant activity of carotenes is well correlated to their electron-donating capacity, which itself largely depends on the length of the conjugated polyene chain. By contrast, the IE of xanthophylls is poorly correlated to the polyene chain length because of the strong, and sometimes unexpected, electronic effects of the O-atoms. Although IE remains an approximate predictor of the antioxidant activity of xanthophylls, other factors (interaction with the aqueous phase, competing radical-scavenging mechanisms, the residual activity of the antioxidant's oxidation products) probably play a significant role.

Production of asymmetric oxidative metabolites of [13C]-ß-carotene during digestion in the gastrointestinal lumen of healthy men.

Background: Asymmetric ß-apo-carotenoids (nonvitamin A-active metabolites) of provitamin A carotenoids have been observed in humans, but no study has investigated their formation during digestion. Objective: The aim of this study was to follow the formation and absorption of asymmetric ß-apo-carotenoids during digestion. Design: Healthy men were intragastrically and intraduodenally intubated, and randomly assigned to consume a lipid-rich control meal (n = 3) or a lipid-rich test meal containing 20 mg [13C-10]-ß-carotene (n = 7). Digesta samples were collected over 5 h, and blood collected over 7 h. The triglyceride-rich lipoprotein (TRL) fractions of plasma were also isolated. Lipophilic extracts of digesta, plasma, and TRL were analyzed via a high-performance liquid chromatography-tandem mass spectrometry method developed to identify [13C]-labeled ß-apo-carotenals/carotenone, [13C]-ß-apo-carotenols, and [13C]-ß-apo-carotenoic acids. Results: Relative to [13C]-ß-carotene, [13C]-ß-apo-carotenal levels remained ∼3 orders of magnitude lower throughout digestion (no [13C]-ß-apo-carotenols, or [13C]-ß-apo-carotenoic acids were observed). A mixed model determined relative influence of digesta type and time on digesta metabolite level. Increasing time significantly increased the model levels of digesta [13C]-ß-apo-10',12',14',15-carotenal and [13C]-ß-apo-13-carotenone (P < 0.05) and trended toward decreased [13C]-ß-apo-8'-carotenal (P = 0.0876). Gastric digesta were associated with a significantly higher level of [13C]-ß-apo-8'-carotenal (P = 0.0289), and lower levels of [13C]-ß-apo-12',14',15-carotenal (P < 0.05), relative to duodenal digesta. Anticipated retinoids, but no asymmetric [13C]-ß-apo-carotenals, [13C]-ß-apo-carotenols, or [13C]-ß-apo-carotenoic acids, were observed in the blood or TRL samples. Conclusions: ß-Carotene appears to be robust to digestion, with minor amounts of ß-apo-carotenals/carotenone formed. Absence of asymmetric [13C]-ß-apo-carotenals in plasma and TRL suggests lack of absorption, levels below the limit of detection, lack of stability, or further conversion during the digestive process to as-yet unidentified products. Lack of asymmetric [13C]-ß-apo-carotenals in plasma also suggests a lack of postprandial intestinal BCO2 activity in healthy humans. This trial was registered at clinicaltrials.gov as NCT03492593.

Opposite Effects of the Spinach Food Matrix on Lutein Bioaccessibility and Intestinal Uptake Lead to Unchanged Bioavailability Compared to Pure Lutein.

SCOPE: Food matrix is generally believed to alter carotenoid bioavailability, but its effect on xanthophylls is usually limited. This study thus aims to decipher the digestion-absorption process of lutein in the presence or not of a food matrix. METHODS: Lutein transfer to gastric-like lipid droplets or artificial mixed micelles was assessed when lutein was added to test meals either as a pure molecule ((all-E)-lutein) or in canned spinach ((Z) + (all-E)-lutein). The obtained mixed micelles were delivered to Caco-2 cells to evaluate lutein uptake. Finally postprandial plasma lutein responses were compared in minipigs after the two test meals. RESULTS: Lutein transfer to gastric-like lipid droplets and to mixed micelles was higher when lutein was added in spinach than when it was added as pure lutein (+614% and +147%, respectively, p < 0.05). Conversely, lutein uptake was less effective when micellar lutein was from a meal containing spinach than from a meal containing its pure form (-55%, p < 0.05). In minipigs, postprandial lutein response was delayed with spinach but not significantly different after the two test meals. CONCLUSION: Opposite effects at the micellarization and intestinal cell uptake steps explain the lack of effect of spinach matrix on lutein bioavailability.

Dietary antioxidants as inhibitors of the heme-induced peroxidation of linoleic acid: mechanism of action and synergism.

In this work, a quantitative kinetic model for investigating the heme-induced peroxidation of linoleic acid and its inhibition by two important dietary antioxidants, quercetin and alpha-tocopherol, is developed. The main conclusions of this work are: (1) The time dependence of the lipid hydroperoxide concentration is critically dependent on the rate constant for lipid hydroperoxide cleavage, initial fraction of lipid hydroperoxides among the pool of conjugated dienes, and rate of heme degradation. (2) The lipophilic antioxidant alpha-tocopherol acts as a chain-breaking antioxidant that quickly reduces 1-2 eq of lipid peroxyl radicals (inhibition of propagation), whereas the more hydrophilic antioxidant quercetin is only marginally chain-breaking but capable of reducing 4-5 eq of iron-oxo initiator (inhibition of initiation). (3) Based on comparisons between experimental peroxidation curves and simulated curves assuming additivity, it can be concluded that combinations of alpha-tocopherol and quercetin are generally synergistic. The kinetic analysis and HPLC titrations of the antioxidants both suggest that synergism mainly arises from a capacity of alpha-tocopherol to regenerate some quercetin oxidation products still endowed with a reducing activity.

Serum from rats fed red or yellow tomatoes induces Connexin43 expression independently from lycopene in a prostate cancer cell line.

Epidemiologic studies suggested a protective effect of tomatoes against prostate cancer brought by lycopene, a carotenoid conferring the red colour of tomatoes. However, intervention studies on patients have shown that the preventive effect of tomato was more potent than that of lycopene. The aim of this study was to compare the effects of red tomato, yellow tomato (devoid of lycopene) and lycopene on Connexin43 (Cx43) expression, a protein regulating cell growth, on a prostate cancer cell line expressing the androgen receptor. Cells were incubated with serum from rats fed a control diet (CS) or control diet supplemented with red tomato (RTS), yellow tomato (YTS) or lycopene beadlets (LBS). After exposure of the cells to RTS or YTS for 48h, the expression of Cx43 was significantly increased compared to cells exposed to CS. Whereas LBS effect was not significantly different. The cells incubated with RTS and LBS had similar levels of lycopene, while those incubated with YTS contained no lycopene. These data first show that serum nutritionally enriched with red and yellow tomatoes could up-regulate Cx43 turn-over in PC3AR cells independently from lycopene level. Within the physiological approach used in the present study, it can be concluded that compounds other than lycopene contribute to the preventive effect of tomatoes.