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The potential beneficial or adverse affect of prolonged dietary administration of moderate to high doses (1–100 mg/kg diet) of the antioxidants, lycopene, quercetin and resveratrol or a mixture of lycopene and quercetin was investigated in male F344 rats. Selected markers for toxicity and defense mechanisms were assayed in blood, liver and colon and the impact of the antioxidant administrations on putative preneoplastic changes in liver and colon was assessed. The dietary carcinogen, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) (200 mg/kg diet) served as a pro-oxidant, genotoxicity and general toxicity control. IQ increased the levels of protein and DNA oxidation products in plasma, the area of glutathione S-transferase-placental form positive (GST-P) foci in the liver as well as the number of colonic aberrant crypt foci (ACF). All antioxidants and the antioxidant combination significantly increased the level of lymphocytic DNA damage, to an extent comparable with the effect induced by IQ. In contrast to the control group where no GST-P foci were detected, GST-P foci were detected in animals exposed to quercetin, lycopene and the combination of the two. However, the increase in the volume of GST-P foci did not reach statistical significance. The present results indicate that moderate to high doses of common dietary antioxidants can damage lymphocyte DNA and induce low levels of preneoplastic liver lesions in experimental animals. Long-term exposure to moderate to high doses of antioxidants may thus via pro-oxidative mechanisms and non-oxidative mechanisms modulate carcinogenesis.

Metmyoglobin, MbFe(III), activated with hydrogen peroxide to yield a hypervalent iron(IV) haem protein with or without a protein-based radical (•MbFe(IV)=O, or MbFe(IV)=O, respectively), was reacted with tyrosine in aqueous solution (5.6

Ambient particulate air pollution assessed as outdoor concentrations of particulate matter less than or equal to 2.5 micro m in diameter (PM(2.5)) in urban background has been associated with cardiovascular diseases at the population level. However, the significance of individual exposure and the involved mechanisms remain uncertain. We measured personal PM(2.5) and carbon black exposure in 50 students four times in 1 year and analyzed blood samples for markers of protein and lipid oxidation, for red blood cell (RBC) and platelet counts, and for concentrations of hemoglobin and fibrinogen. We analyzed protein oxidation in terms of gamma-glutamyl semialdehyde in hemoglobin (HBGGS) and 2-aminoadipic semialdehyde in hemoglobin (HBAAS) and plasma proteins (PLAAS), and lipid peroxidation was measured as malondialdehyde (MDA) in plasma. Median exposures were 16.1 micro g/m(3) for personal PM(2.5) exposure, 9.2 micro g/m(3) for background PM(2.5) concentration, and 8.1 X 10(-6)/m for personal carbon black exposure. Personal carbon black exposure and PLAAS concentration were positively associated (p < 0.01), whereas an association between personal PM(2.5) exposure and PLAAS was only of borderline significance (p = 0.061). A 3.7% increase in MDA concentrations per 10 micro g/m(3) increase in personal PM(2.5) exposure was found for women (p < 0.05), whereas there was no significant relationship for the men. Similarly, positive associations between personal PM(2.5)exposure and both RBC and hemoglobin concentrations were found only in women (p < 0.01). There were no significant relationships between background PM(2.5) concentration and any of the biomarkers. This suggests that exposure to particles in moderate concentrations can induce oxidative stress and increase RBCs in peripheral blood. Personal exposure appears more closely related to these biomarkers potentially related to cardiovascular disease than is ambient PM(2.5) background concentrations.

The contribution of oxidative stress, different types of DNA damage and expression of DNA repair enzymes in colon and liver mutagenesis induced by 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) was investigated in four groups of six Big Blue rats fed diets with 0, 20, 70, and 200 mg IQ/kg for 3 weeks. There were dose-response relationships of DNA adducts ((32)P-postlabeling) and DNA strand breaks (comet assay) in colon and liver tissues, with the highest levels of DNA adducts and strand breaks in the colon. There was dose-dependent induction of mutations in both the colon and the liver, and the same IQ dose produced two-fold more cII mutations in the liver compared with the colon. The IQ-induced mutation spectrum in the colon was not significantly different to that of control rats. The expression of ERCC1 and OGG1 was higher in the colon than liver, and was unaffected by the IQ diet. Investigations of oxidative stress biomarkers produced inconclusive results. Oxidative DNA damage detected by the endonuclease III enzyme and 7-hydro-8-oxo-2'-deoxyguanosine in colon, liver and/or urine was unaltered by IQ. However, there was increased level of gamma-glutamyl semialdehyde in liver proteins, indicating a higher rate of protein oxidation in the liver following IQ administration. In plasma and erythrocytes there were unaltered levels of oxidized protein, malondialdehyde, and antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, catalase, glutathione reductase) indicating no systemic oxidative stress. However, the level of total vitamin C was increased in plasma, with the largest fraction being in the reduced form. In conclusion, our results indicate that DNA adducts rather than oxidative stress are responsible for the initiation of IQ-induced carcinogenesis of the liver and colon. A lower frequency of mutations in the colon than in the liver could be related to higher expression of DNA repair enzymes in the former.

Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2×3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18·6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1·35 to 1·56 (P

Seven men and seven women participated in a randomized crossover trial to study the effect of intake of parsley (Petroselinum crispum), containing high levels of the flavone apigenin, on the urinary excretion of flavones and on biomarkers for oxidative stress. The subjects received a strictly controlled diet low in flavones and other naturally occurring antioxidants during the 2 weeks of intervention. This basic diet was supplemented with parsley providing 3·73–4·49 mg apigenin/MJ in one of the intervention weeks. Urinary excretion of apigenin was 1·59–409·09 μg/MJ per 24 h during intervention with parsley and 0–112·27 μg/MJ per 24 h on the basic diet (P < 0·05). The fraction of apigenin intake excreted in the urine was 0·58 (se 0·16) % during parsley intervention. Erythrocyte glutathione reductase (EC 1.6.4.1; GR) and superoxide dismutase (EC 1.15.1.1; SOD) activities increased during intervention with parsley (P < 0·005) as compared with the levels on the basic diet, whereas erythrocyte catalase (EC 1.11.1.6) and glutathione peroxidase (EC 1.11.1.9) activities did not change. No significant changes were observed in plasma protein 2-adipic semialdehyde residues, a biomarker of plasma protein oxidation. In this short-term investigation, an overall decreasing trend in the activity of antioxidant enzymes was observed during the 2-week study. The decreased activity of SOD was strongly correlated at the individual level with an increased oxidative damage to plasma proteins. However, the intervention with parsley seemed, partly, to overcome this decrease and resulted in increased levels of GR and SOD.

Exposure to diesel exhaust particles (DEP) via the gastrointestinal route may impose risk of cancer in the colon and liver. We investigated the effects of DEP given in the diet to Big Blues rats by quantifying a panel of markers of DNA damage and repair, mutation, oxidative damage to proteins and lipids, and antioxidative defence mechanisms in colon mucosa cells, liver tissue and the blood compartment. Seven groups of rats were fed a diet with 0, 0.2, 0.8, 2, 8, 20 or 80 mg DEP/kg feed for 21 days. DEP induced a significant increase in DNA strand breaks in colon and liver. There was no effect on oxidative DNA damage (8-oxodG) in colon or liver DNA or in the urine. However, the mRNA expression of OGGI, encoding an enzyme involved in repair of 8-oxodG, was increased by DEP in both liver and colon. DNA adduct levels measured by 32 P-post-labelling were elevated in colon and liver, and the expression of ERCCI gene was affected in liver, but not in colon. In addition to these effects, DEP exposure induced apoptosis in liver. There was no significant change in mutation frequency in colon or liver. The levels of oxidative protein modifications (oxidized arginine and proline residues) were increased in liver accompanied by enhanced vitamin C levels. In plasma, we found no significant effects on oxidative damage to proteins and lipids, antioxidant enzymes or vitamin C levels. Our data indicate that gastrointestinal exposure to DEP induces DNA adducts and oxidative stress resulting in DNA strand breaks, enhanced repair capacity of oxidative base damage, apoptosis and protein oxidation in colon mucosa cells and liver.

Artichoke (Cynara scolymus L.), an edible vegetable from the Mediterranean area, is a good source of natural antioxidants such as vitamin C, hydroxycinnamic acids, and flavones. The antioxidant activity of aqueous-organic extracts of artichoke were determined using three methods: (a) free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH.) scavenging, (b) ferric-reducing antioxidant power (FRAP), and (c) inhibition of copper(II)-catalyzed in vitro human low-density lipoprotein (LDL) oxidation. In addition, the present study was performed to investigate the ability of the edible portion of artichoke to alter in vivo antioxidative defense in male rats using selected biomarkers of antioxidant status. One gram (dry matter) had a DPPH. activity and a FRAP value in vitro equivalent to those of 29.2 and 62.6 mg of vitamin C and to those of 77.9 and 159 mg of vitamin E, respectively. Artichoke extracts showed good efficiency in the inhibition in vitro of LDL oxidation. Neither ferric-reducing ability nor 2,2′-azinobis-(3-ethylbenzothiazolin-6-sulfonate) radical scavenging activity was modified in the plasma of the artichoke group with respect to the control group. Among different antioxidant enzymes measured (superoxide dismutase, gluthatione peroxidase, gluthatione reductase, and catalase) in erythrocytes, only gluthatione peroxidase activity was elevated in the artichoke group compared to the control group. 2-Aminoadipic semialdehyde, a protein oxidation biomarker, was decreased in plasma proteins and hemoglobin in the artichoke-fed group versus the control group. In conclusion, the in vitro protective activity of artichoke was confirmed in a rat model.

Administration of apple juice, black currant juice, or a 1:1 combination of the two juices significantly decreased the level of the lipid peroxidation biomarker malondialdehyde in plasma of female rats, whereas the protein oxidation biomarker 2-amino-adipic semialdehyde, was significantly increased following administration of orange juice, black currant juice, or the 1:1 combination of apple and black currant juice. A significant increase in 2-amino-adipic semialdehyde was also observed in control rats given sucrose, fructose, and glucose in the drinking water at concentrations approximating the average carbohydrate levels in the employed fruit juices. None of the fruit juices were found to affect the activities of antioxidant enzymes in red blood cells or hepatic glutathione S-transferase. Hepatic quinone reductase activity, on the other hand, was significantly increased by grapefruit juice, apple juice, and black currant juice. The total daily intake of a selected subset of flavonoid aglycones ranged from 0.2 to 4.3 mg, and quercetin was found to be a minor constituent of all the juices investigated. In a parallel study, rats were fed quercetin at doses ranging from 0.001 to 10 g/kg of diet. However, no effects were observed on hepatic glutathione S-transferase or quinone reductase activities, plasma redox status, or the activity of red blood cell antioxidant enzymes. Overall, the results of the present study suggest that commonly consumed fruit juices can alter lipid and protein oxidation biomarkers in the blood as well as hepatic quinone reductase activity, and that quercetin may not be the major active principle. The observation that natural carbohydrates are capable of mediating oxidative stress in vivo warrants further studies due to the central role refined and unrefined carbohydrates play in human nutrition.

A sucrose-rich diet has repeatedly been observed to have cocarcinogenic actions in the colon and liver of rats and to increase the number of aberrant crypt foci in rat colon. To investigate whether sucrose-rich diets might directly increase the genotoxic response in the rat colon or liver, we have added sucrose to the diet of Big Blue rats, a strain of Fischer rats carrying 40 copies of the lambda-phage on chromosome 4. Dietary sucrose was provided to the rats for 3 weeks at four dose levels including the background level in the purified diet [3.4% (control), 6.9%, 13.8%, or 34.5%] without affecting the overall energy and carbohydrate intake. We observed a dose-dependent increase in the mutation frequency at the cII site in the colonic mucosa with increased sucrose levels, reaching a 129% increase at the highest dose level. This would indicate a direct or indirect genotoxic effect of a sucrose-rich diet. No significant increase in mutations was observed in the liver. To seek an explanation for this finding, a variety of parameters were examined representing different mechanisms, including increased oxidative stress, changes in oxidative defense, effects on DNA repair, or changes in the background levels of DNA adducts. Sucrose did not increase the number of DNA strand breaks or oxidized bases assessed as endonuclease III-sensitive sites or 8-oxodeoxyguanosine in colon or liver. DNA repair capacity as determined by expression of the rERCC1 or rOGG1 genes was not increased in colon or liver, but the background level of DNA adducts (I-compounds) as determined by (32)P postlabeling was significantly decreased in colon. This decrease in colon I-compounds correlated inversely with both mutation frequency and ERCC1 DNA repair gene expression. Dietary sucrose did not change liver apoptosis or cell turnover as determined by the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end labeling assay and proliferating cell nuclear antigen. An increase in liver ascorbate was also observed, whereas oxidative damage was not observed in proteins or lipids in liver cytosol or in blood plasma. We conclude that a sucrose-rich diet directly or indirectly increases the mutation frequency in rat colon in a dose-dependent manner and concomitantly decreases the level of background DNA adducts, without a direct effect on the expression of major DNA repair enzyme systems. We also conclude that an oxidative mechanism for this effect of sucrose is unlikely. This is the first demonstration of a genotoxic action of increased dietary sucrose in vivo. Both sucrose intake and colon cancer rates are high in the Western world, and our present results call for an examination of a possible direct relationship between the two.

Reduction of iron (IV) in ferrylmyoglobin in the presence of beta-lactoglobulin in aqueous solution is the result of two parallel reactions: (i) a so-called autoreduction, and (ii) reduction by beta-lactoglobulin in a second-order-reaction resulting in bityrosine formation in beta- lactoglobulin. In the pH-region investigated (5.4-7.4), the rate of reduction increased for both reactions with decreasing pH. The second order-reaction had for non-denatured beta-lactoglobulin the activation parameters: delta H* = 45 kJ.mol-1 and delta S not equal to = -93 J.mol-1.K-1 at pH = 7.0 and ionic strength 0.16 (NaCl). Reduction of ferrylmyoglobin by beta-lactoglobulin denatured by heat (86 degrees C for 3 min) or by hydrostatic pressure (300 MPa for 15 min) resulted in formation of higher molecular weight species as detected by size-exclusion chromatography and by SDS-PAGE. No molecular weight changes were observed for reduction of ferrylmyoglobin by native beta-lactoglobulin. Detection of bityrosine in the native beta-lactoglobulin fraction after oxidation with ferrylmyoglobin indicated intra-molecular bityrosine formation. In heat-denatured beta-lactoglobulin bityrosine formation could be of intra-molecular and/or of inter-molecular origin, the latter being confirmed by size-exclusion chromatography.

A new optical resonator based on the combination of a generalized self-filtering unstable resonator (GSFUR) and a positive-branch unstable resonator (PBUR) in a three-mirror scheme is reported. It is shown both theoretically and experimentally that a nearly diffraction-limited Gaussian-output laser beam with a large mode volume can be obtained with this cavity design. The laser cavity is particularly interesting for use in high-threshold pumped gain media and eliminates some disadvantages of the SFUR and GSFUR designs. This resonator, with an effective magnification of -6.16, was applied to a pulsed Nd:YAG laser in free-running and in Q-switched modes of operation. The output energy was approximately 70 mJ, 5.5 times greater than when a single GSFUR design was used. The output beam had a pulse duration of approximately 30 ns in the Q-switched mode of operation and a beam divergence of 0.26 mrad. The required relations for the GSFUR-PBUR optical design and the output energy were derived and verified experimentally.

The health effects of diesel exhaust particles (DEP) are thought to involve oxidative damage. We have investigated the effect of intratracheal DEP instillation to guinea pigs in three groups of 12 animals each given 0, 0.7, or 2.1 mg. Five days later guinea pigs exposed to DEP had increased levels of oxidized amino acids (γ-glutamyl semialdehyde), DNA strand breaks, and 7-hydro-8-oxo-2′-deoxyguanosine (8-oxodG) in the lung. Bulky DNA ad- ducts were not significantly elevated in the lung. The antioxidant enzyme activity of glutathione reductase was increased in the lung of DEP-exposed guinea pigs, whereas glutathione peroxidase and superoxide dismutase enzyme activities were unaltered. There was no difference in DNA strand breaks in lymphocytes or urinary excretion of 8-oxodG at the two doses tested. Protein oxidations in plasma and in erythrocytes were not altered by DEP exposure. The concentrations of ascorbate in liver, lung, and plasma were unaltered by the DEP exposure. The results indicate that in guinea pigs DEP causes oxidative DNA damage rather than bulky DNA adducts in the lung. Guinea pigs, which are similar to humans with respect to vitamin C metabolism, may serve as a new model for the study of oxidative damage induced by particulate matter.

The administration of lycopene to female rats at doses ranging from 0.001 to 0.1 g/kg b.w. per day for 2 weeks was found to alter the drug-metabolizing capacity and antioxidant status of the exposed animals. An investigation of four cytochrome P450-dependent enzymes revealed that benzyloxyresorufin O-dealkylase activity in the liver was significantly induced in a dose-dependent fashion at all lycopene doses investigated. Likewise, ethoxyresorufin O-dealkylase activity was induced, although only at the two highest lycopene concentrations tested. An investigation of selected phase 2 detoxification enzymes provided evidence that lycopene was capable of inducing hepatic quinone reductase, approximately two-fold, at doses between 0.001 and 0.05 g/kg b.w. per day, whereas no effect was observed at the remaining doses tested. Glutathione transferase, using the two substrates, 2,4-dichloronitrobenzene and 1-chloro-2, 4-dinitrobenzene, was significantly induced at the 0.1 g/kg b.w. per day dose, whereas no effect was observed at the remaining lycopene doses. Analysis of the antioxidant status of the blood compartment revealed that three out of four antioxidant enzymes were affected by lycopene treatment. The activity of superoxide dismutase was thus significantly induced at lycopene doses of 0.005 and 0.05 g/kg b.w, whereas glutathione reductase and glutathione peroxidase was only induced at the 0.005 g/kg b.w. per day dose. For all antioxidant enzymes investigated, the activities seemed to return to the control level after exerting peak induction at doses between 0.005 and 0.05 g/kg b.w. per day. The explanation for this remains unknown. The plasma concentration of lycopene at dietary levels of 0.001, 0.005, 0.05 and 0.1 g/kg b.w. per day was estimated to be 16, 32, 71 and 67 nM, which is barely within the lower range of the mean human plasma concentration of lycopene, which ranges from 70-1790 nM. Oxidative stress induced by the heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), and investigated by analyzing for malondialdehyde in plasma, was not found to be affected by prior lycopene exposure. The level of PhIP-DNA adducts in the liver or colon was likewise not affected by lycopene at any dose. Overall, the present study provides evidence that lycopene administered in the diet of young female rats exerts minor modifying effects toward antioxidant and drug-metabolizing enzymes involved in the protection against oxidative stress and cancer. The fact that these enzymatic activities are induced at all of these very low plasma levels, could be taken to suggest that modulation of antioxidant and drug-metabolizing enzymes may indeed be relevant to humans, which in general exhibit a plasma lycopene level several fold above the effective levels observed in this study.

Background Epidemiologic studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease. Objective Our objective was to investigate the effect of intake of flavonoid-containing black currant and apple juice on urinary excretion of quercetin and on markers of oxidative status. Design This was a crossover study with 3 doses of juice (750, 1000, and 1500 mL) consumed for 1 wk by 4 women and 1 man corresponding to an intake of 4.8, 6.4, and 9.6 mg quercetin/d. Results Urinary excretion of quercetin increased significantly with dose and with time. The fraction excreted in urine was 0.29-0.47%. Plasma quercetin did not change with juice intervention. Plasma ascorbate increased during intervention because of the ascorbate in the juice. Total plasma malondialdehyde decreased with time during the 1500-mL juice intervention, indicating reduced lipid oxidation in plasma. Plasma 2-amino-adipic semialdehyde residues increased with time and dose, indicating a prooxidant effect of the juice, whereas erythrocyte 2-aminoadipic semialdehyde and gamma-glutamyl semialdehyde concentrations, Trolox-equivalent antioxidant capacity, and ferric reducing ability of plasma did not change. Glutathione peroxidase activity increased significantly with juice dose. Conclusions Urinary excretion of quercetin seemed to be a small but constant function of quercetin intake. Short-term, high intake of black currant and apple juices had a prooxidant effect on plasma proteins and increased glutathione peroxidase activity, whereas lipid oxidation in plasma seemed to decrease. These effects might be related to several components of the juice and cannot be attributed solely to its quercetin content.

A sucrose-rich diet has repeatedly been observed to have cocarcinogenic actions in the colon and liver of rats and to increase the number of aberrant crypt foci in rat colon. To investigate whether sucrose-rich diets might directly increase the genotoxic response in the rat colon or liver, we have added sucrose to the diet of Big Blue rats, a strain of Fischer rats carrying 40 copies of the lambda-phage on chromosome 4. Dietary sucrose was provided to the rats for 3 weeks at four dose levels including the background level in the purified diet [3.4% (control), 6.9%, 13.8%, or 34.5%] without affecting the overall energy and carbohydrate intake. We observed a dose-dependent increase in the mutation frequency at the cII site in the colonic mucosa with increased sucrose levels, reaching a 129% increase at the highest dose level. This would indicate a direct or indirect genotoxic effect of a sucrose-rich diet. No significant increase in mutations was observed in the liver. To seek an explanation for this finding, a variety of parameters were examined representing different mechanisms, including increased oxidative stress, changes in oxidative defense, effects on DNA repair, or changes in the background levels of DNA adducts. Sucrose did not increase the number of DNA strand breaks or oxidized bases assessed as endonuclease III-sensitive sites or 8-oxodeoxyguanosine in colon or liver. DNA repair capacity as determined by expression of the rERCC1 or rOGG1 genes was not increased in colon or liver, but the background level of DNA adducts (I-compounds) as determined by (32)P postlabeling was significantly decreased in colon. This decrease in colon I-compounds correlated inversely with both mutation frequency and ERCC1 DNA repair gene expression. Dietary sucrose did not change liver apoptosis or cell turnover as determined by the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end labeling assay and proliferating cell nuclear antigen. An increase in liver ascorbate was also observed, whereas oxidative damage was not observed in proteins or lipids in liver cytosol or in blood plasma. We conclude that a sucrose-rich diet directly or indirectly increases the mutation frequency in rat colon in a dose-dependent manner and concomitantly decreases the level of background DNA adducts, without a direct effect on the expression of major DNA repair enzyme systems. We also conclude that an oxidative mechanism for this effect of sucrose is unlikely. This is the first demonstration of a genotoxic action of increased dietary sucrose in vivo. Both sucrose intake and colon cancer rates are high in the Western world, and our present results call for an examination of a possible direct relationship between the two.

Epidemiological studies indicate that moderate alcohol consumption, particularly wine, reduce the risk of CHD. The present study was designed to investigate the effect of grape-skin extract on markers of oxidative status. The study was designed as a randomised crossover. A diet with a low content of flavonoids was served with strict control of intake in two consecutive 1-week intervention periods to fifteen subjects (nine women, six men) divided randomly into two groups. During one of the weeks the subjects from either group consumed 200 ml grape-skin extract in water (1 mg extract/ml) at each of three daily meals (31·3 mg total phenolics, including 9·0 mg catechin). An increased activity of glutathione reductase and a borderline increase of glutathione peroxidase activity in erythrocytes were observed after grape-skin intervention, while the intervention had no significant effect on superoxide dismutase or catalase. Likewise, no effect was found on 2-aminoadipic semialdehyde (AAS) residues, a plasma protein oxidation product, or on malondialdehyde in plasma or in LDL, which are markers of lipoprotein oxidation. A marginal effect of grape-skin intervention was observed on plasma ascorbate levels. Intake of the experimental diet significantly reduced plasma vitamin C and plasma AAS in both groups. This effect was most pronounced in the particular week with no grape-skin extract addition. We speculate that grape-skin extract may have a sparing effect on vitamin C. The effects of the experimental diet may be partly ascribed to a low content of several fruit- and vegetable-related antioxidants like flavonoids and vitamin C and a relatively high content of carrot-derived antioxidants, such as carotenes.