Orange juice (poly)phenols are highly bioavailable in humans

BACKGROUND

We assessed the bioavailability of orange juice (poly)phenols by monitoring urinary flavanone metabolites and ring fission catabolites produced by the action of the colonic microbiota.

OBJECTIVE

Our objective was to identify and quantify metabolites and catabolites excreted in urine 0-24 h after the acute ingestion of a (poly)phenol-rich orange juice by 12 volunteers.

DESIGN

Twelve volunteers [6 men and 6 women; body mass index (in kg/m(2)): 23.9-37.2] consumed a low (poly)phenol diet for 2 d before first drinking 250 mL pulp-enriched orange juice, which contained 584 μmol (poly)phenols of which 537 μmol were flavanones, and after a 2-wk washout, the procedure was repeated, and a placebo drink was consumed. Urine collected for a 24-h period was analyzed qualitatively and quantitatively by using high-performance liquid chromatography-mass spectrometry (HPLC-MS) and gas chromatography-mass spectrometry (GC-MS).

RESULTS

A total of 14 metabolites were identified and quantified in urine by using HPLC-MS after orange juice intake. Hesperetin-O-glucuronides, naringenin-O-glucuronides, and hesperetin-3'-O-sulfate were the main metabolites. The overall urinary excretion of flavanone metabolites corresponded to 16% of the intake of 584 μmol (poly)phenols. The GC-MS analysis revealed that 8 urinary catabolites were also excreted in significantly higher quantities after orange juice consumption. These catabolites were 3-(3'-methoxy-4'-hydroxyphenyl)propionic acid, 3-(3'-hydroxy-4'-methoxyphenyl)propionic acid, 3-(3'-hydroxy-4'-methoxyphenyl)hydracrylic acid, 3-(3'-hydroxyphenyl)hydracrylic acid, 3'-methoxy-4'-hydroxyphenylacetic acid, hippuric acid, 3'-hydroxyhippuric acid, and 4'-hydroxyhippuric acid. These aromatic acids originated from the colonic microbiota-mediated breakdown of orange juice (poly)phenols and were excreted in amounts equivalent to 88% of (poly)phenol intake. When combined with the 16% excretion of metabolites, this percentage raised the overall urinary excretion to ∼ 100% of intake.

CONCLUSIONS

When colon-derived phenolic catabolites are included with flavanone glucuronide and sulfate metabolites, orange juice (poly)phenols are much-more bioavailable than previously envisaged. In vitro and ex vivo studies on mechanisms underlying the potential protective effects of orange juice consumption should use in vivo metabolites and catabolites detected in this investigation at physiologic concentrations. The trial was registered at BioMed Central Ltd (www.controlledtrials.com) as ISRCTN04271658.

Wheat aleurone polyphenols increase plasma eicosapentaenoic acid in rats

Methods

These studies were designed to assess whether wheat polyphenols (mainly ferulic acid [FA]) increased the very-long-chain omega-3 fatty acids (VLC n-3) [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] in rats. Wheat aleurone (WA) was used as a dietary source of wheat polyphenols. Two experiments were performed; in the first one, the rats were fed WA or control pellets (CP) in presence of linseed oil (LO) to provide alpha-linolenic acid (ALA), the precursor of VLC n-3. In the second one, the rats were fed WA or CP in presence of control oil (CO) without ALA. The concentrations of phenolic acid metabolites in urine were also investigated.

Results

The urinary concentration of conjugated FA increased with WA ingestion (p<0.05). Plasma EPA increased by 25% (p<0.05) with WA in the CO group but not in the LO group. In contrast, there was no effect of WA on plasma DHA and omega-6 fatty acids (n-6). Finally, both n-3 and n-6 in the liver remained unchanged by the WA.

Conclusion

These results suggest that WA consumption has a significant effect on EPA in plasma without affecting n-6. Subsequent studies are required to examine whether these effects may explain partly the health benefits associated with whole wheat consumption.

Modeling the effect of phase II conjugations on topoisomerase I poisoning: pilot study with luteolin and quercetin

Topoisomerases are targeted by several drugs in cancer chemotherapy acting as key enzymes in cell viability. Some flavonoids and their glycosides may exert health protective effects through the poisoning of topoisomerases. However, previous studies did not consider the substantial modifications taking place after ingestion neglecting that only metabolites can interact with the internal compartments of the human body. Since the high number of possible metabolites hinders their systematic analysis, an in silico approach can be a valuable tool to prioritize compounds by identifying candidates for further characterization. Specifically focusing on luteolin and quercetin, among the most ubiquitous flavonoids in the human diet, this work reports a computational procedure to model the effect of hepatic phase II conjugative metabolism on poisoning of human Topoisomerase I. As a general effect, glucuronidation and sulphation might enhance and quench poisoning activity, respectively. Among all, quercetin-3-O-glucuronide represents a promising candidate to be analyzed more thoroughly.

Absorption, metabolism, and excretion of fermented orange juice (poly)phenols in rats

Two milliliters of a fermented, pasteurized orange juice containing ~1% alcohol and 2.3 μmol of (poly)phenolic compounds was fed to rats by gavage after which plasma and urine collected over a 36 h period were analyzed by UHPLC-mass spectrometry. The main constituents in the juice were hesperetin and naringenin-O-glycosides, apigenin-6,8-C-diglucoside, and ferulic acid-4'-O-glucoside. Plasma contained seven flavanone glucuronides, with the principal metabolites, naringenin-7-O-glucuronide, naringenin-4'-O-glucuronide, and an isosakuranetin-O-glucuronide, peaking 6 h after intake at concentrations of ~10 nmol/L. Urinary excretion of four hesperetin glucuronides was equivalent to 0.28% of intake while that of the two naringenin glucuronides was 2.8% of intake. The plasma and urine data suggest that while some absorption occurred in the small intestine, the main site of uptake was the colon. Urine also contained dihydroferulic acid-4'-O-glucuronide and dihydroferulic acid-4'-O-sulfate which were excreted in quantities corresponding to 48.2% of the ingested ferulic acid-4'-glucoside. This indicates that the hydroxycinnamate is much more bioavailable than the flavanones in the rat model. Conversion of the ferulic acid glucoside to the dihydroferulic acid metabolites involves the action of colonic microbial glycosidases and reductases/hydrogenases followed by postabsorption phase II metabolism before renal excretion.

Glucuronidation does not suppress the estrogenic activity of quercetin in yeast and human breast cancer cell model systems

Several plant-derived molecules, referred to as phytoestrogens, are thought to mimic the actions of endogenous estrogens. Among these, quercetin, one of the most widespread flavonoids in the plant kingdom, has been reported as estrogenic in some occasions. However, quercetin occurs in substantial amounts as glycosides such as quercetin-3-O-glucoside (isoquercitrin) and quercetin-3-O-rutinoside (rutin) in dietary sources. It is now well established that quercetin undergoes substantial phase II metabolism after ingestion by humans, with plasma metabolites after a normal dietary intake rarely exceeding nmol/L concentrations. Therefore, attributing phytoestrogenic activity to flavonoids without taking into account the fact that it is their phase II metabolites that enter the circulatory system, will almost certainly lead to misleading conclusions. With the aim of clarifying the above issue, the goal of the present study was to determine if plant-associated quercetin glycosides and human phase II quercetin metabolites, actually found in human biological fluids after intake of quercetin containing foods, are capable of interacting with the estrogen receptors (ER). To this end, we used a yeast-based two-hybrid system and an estrogen response element-luciferase reporter assay in an ER-positive human cell line (MCF-7) to probe the ER interaction capacities of quercetin and its derivatives. Our results show that quercetin-3-O-glucuronide, one of the main human phase II metabolites produced after intake of dietary quercetin, displays ERα- and ERβ-dependent estrogenic activity, the functional consequences of which might be related to the protective activity of diets rich in quercetin glycosides.

In vitro bioaccessibility of phenolics and vitamins from durum wheat aleurone fractions

Durum wheat aleurone, thanks to its nutrient-rich composition, might be of potential use as a functional ingredient in cereal-based foods provided nutrients can be made available for absorption. We evaluated the in vitro bioaccessibility of thiamine, niacin, and phenolic acids in different aleurone fractions obtained with an industrial processing aimed to obtain material of different composition and particle size. Results indicate that the main phenolic compounds and vitamins investigated have a higher bioaccessibility when present in the inner part of the aleurone layer compared to the outer part of aleurone or the unfractionated bran. Moreover, an ultramicronization treatment employed to reduce particle size does not further improve the bioaccessibility of these compounds. We conclude that aleurone fractions from durum wheat bran could represent a nutritionally relevant ingredient, bringing together a high fiber content and an excellent bioaccessibility of vitamins and phytochemicals generally associated with nutritional benefits.

Bioavailability and metabolism of hydroxycinnamates in rats fed with durum wheat aleurone fractions

A specific wheat aleurone fraction showed potentially interesting ferulic acid improved bioavailability and might be used for the formulation of new wheat based products.

Do flavan-3-ols from green tea reach the human brain?

Following acute ingestion of green tea by six human subjects, HPLC-MS2 analysis revealed that flavan-3-ol methyl, glucuronide and sulfate metabolites appeared in the bloodstream but did not pass through the blood-cerebrospinal fluid barrier. These observations emphasize the discrepancies between in vitro and in vivo evidence on the neuroprotective role of these compounds. If, as has been proposed, green tea exerts neuroprotective effects, this finding indicates that the active components are not flavan-3-ols or their metabolites. Alternatively, a systemic action may be hypothesised whereby dietary flavan-3-ols up-regulate antioxidant defences and/or reduce inflammation, the benefit of which may be effective throughout the body.

Assessment of pomegranate wine lees as a valuable source for the recovery of (poly)phenolic compounds

Wine lees are the residue formed at the bottom of recipients containing wine after fermentation and are mainly composed of yeast. They can be applied for the recovery of value-added phytochemicals owing to the ability of yeast to form molecular interactions with (poly)phenolic compounds. This study aimed to evaluate the potential use of lees obtained as by-products after winemaking of pomegranate (Punica granatum L.) juice. Pomegranate wine lees showed high both phenolic content (about 30 mg GAE/g dry matter) and antioxidant capacity by DPPH and ABTS(+) assays. The phytochemical screening of this by-product by UHPLC-ESI-MS(n) allowed the identification of up to 39 chemicals, being hydrolysable tannins and anthocyanins the predominant structures. Ellagic acid and gallic acid were present in high amounts. In addition, mineral composition was also assessed. Overall, pomegranate wine lees resulted in a promising source for the recovery of bioactive polyphenols with potential applications in different industrial fields.

Ultra-HPLC-MS(n) (Poly)phenolic profiling and chemometric analysis of juices from ancient Punica granatum L. Cultivars: a nontargeted approach

This study deals with the qualitative characterization of the phenolic profile of pomegranate juices obtained from ancient accessions. Composition data, together with genetic, morphological, and agronomical parameters, may lead to a full characterization of such germplasm, with the aim of its retrieval and biodiversity valorization. Environmental adaptation, indeed, may contribute to an enrichment of the phenolic content in pomegranate, with important effects on its nutritional properties. More than 65 punicalagins, ellagic acid derivatives, flavonoids, anthocyanins, and phenylpropanoids were simultaneously detected from four centuries old Punica granatum L. ecotypes from northern Italy and compared with those of P. granatum cv. Dente di Cavallo, a widely cultivated Italian cultivar, using a simple ultra-HPLC (uHPLC) separation and MS(n) linear ion trap mass spectrometric characterization. Fingerprinting phytochemical discrimination of the accessions was obtained by chemometric analysis despite their limited geographical distribution, confirming the great intraspecific variability in pomegranate secondary metabolism. The combined recourse to uHPLC-MS(n) qualitative fingerprinting and multivariate analysis may represent a useful tool for the discrimination and selection of pomegranate germplasm with specific properties related to polyphenolic content.

Metabolite profiling of polyphenols in a Terminalia chebula Retzius ayurvedic decoction and evaluation of its chemopreventive activity

ETHNOPHARMACOLOGICAL RELEVANCE

The decoction of Terminalia chebula fruit is an ayurvedic remedy whose prolonged oral administration is prized as a generic intestinal and hepatic detoxifying agent. Its administration is suggested also under the perspective of a reduced risk of cancer, metabolic and cardiovascular diseases.

AIM OF THE STUDY

To evaluate the phytochemical profile and the chemopreventive potential of Terminalia chebula fruit decoction prepared according to the ayurvedic decoction recipe.

MATERIALS AND METHODS

The quali- and quantitative metabolite profiling of polyphenols was obtained using HPLC-UV/DAD and HPLC-ESI-MS. The crude decoction and purified compounds were tested for their capability to interact with the EphA2-ephrin-A1 system and for their antimutagenic properties against dietary and environmental mutagens (AA, 2-NF, NaN3, and heterocyclic amines IQ, MeIQ, MeIQx, Glu-P1, Glu-P2,) in the Ames-Salmonella/microsome assay, with and without enzymatic induction.

RESULTS

The decoction was found to contain 3,4,6-tri-O-galloyl-d-glucose (55.87 mg/g), chebulic acid (54.03 mg/g), β-punicalagin (41.25mg/g), corilagin (40.31 mg/g), α-punicalagin (35.55 mg/g), chebulagic acid (29.09 mg/g), gallic acid (27.96 mg/g) 1,3,4,6-tri-O-galloyl-β-d-glucose (24.25mg/g) chebulinic acid (20.23 mg/g), 1,2,3,4,6-penta-O-galloyl-d-glucose (13.53 mg/g), ellagic acid (8.00 mg/g), 1,6-di-O-galloyl-d-glucose (4.16 mg/g). An inhibitory effect was recorded in both Salmonella typhimurium TA98 and TA100 strains against the mutagenic activity of heterocyclic amines (22-61%), promutagen AA (91-97%) and directly acting mutagen 2-NF (52%) with but not against NaN3 (7%). Galloyl derivatives allowed an inhibition of mutagenicity induced by MeIQ above 80% at 0.01 mol/plate. Both decoction and purified compounds were able to modulate the EphA2-ephrinA1 system, suggesting a potential multiple chemopreventive mechanism.

CONCLUSIONS

The traditional ayurvedic decoction of Terminalia chebula may harbour a potential as a safe and low-cost chemopreventive agent at the intestinal level, if administered according to the ayurvedic specifications. Moreover, its recourse may enhance the presence of some polyphenolic constituents.

Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-μM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

Masked mycotoxins are efficiently hydrolyzed by human colonic microbiota releasing their aglycones

Fusarium mycotoxins are secondary metabolites produced by Fusarium spp. in cereals. Among them, deoxynivalenol (DON) and zearalenone (ZEN) are widespread worldwide contaminants of cereal commodities and are ranked as the most important chronic dietary risk factors. Their conjugates, known as masked mycotoxins, have been described but are still not accounted for in risk assessment studies. This study demonstrates for the first time that DON and ZEN are effectively deconjugated by the human colonic microbiota, releasing their toxic aglycones and generating yet unidentified catabolites. For this reason, masked mycotoxins should be considered when evaluating population exposure.

Absorption and metabolism of milk thistle flavanolignans in humans

This study evaluated the absorption and metabolism of milk thistle flavonolignans silychristin, silydianin, silybin and isosilybin isomers (all together known as silymarin) in humans. Fourteen volunteers consumed an extract of milk thistle and urine was collected up to 48 h after consumption. Thirty-one metabolites were identified in urine by means of HPLC-MS/MS, monoglucuronides being the most common excreted form, followed by sulphate-glucuronides and diglucuronides, respectively. The excretion of monoglucuronides peaked 2 h after consumption, whereas sulphate-glucuronide and diglucuronide excretion peaked at 8 h. The bioavailability of milk thistle flavanolignans was 0.45±0.28% (mean±SD). In conclusion, milk thistle flavonolignans are extensively modified after ingestion and recovered in urine as sulpho- and glucuronyl-conjugates, indicating a strong affinity for hepatic phase II enzymes. All future studies (in vitro and in vivo) dealing with the effects of milk thistle should start by considering the modification of its flavonolignans after ingestion by humans.

Perturbation of the EphA2-EphrinA1 system in human prostate cancer cells by colonic (poly)phenol catabolites

The Eph tyrosine kinase receptors and their ephrin ligands play a central role in human cancer as their deregulated expression induces tumorigenesis with aggressive phenotypes. To evaluate their potential contribution to EphA2-ephrinA1 modulation, several colonic catabolites of dietary (poly)phenolics, known to be generated in vivo, were screened using an ELISA-based binding assay. Some of the catabolites inhibited the binding in a dose-dependent manner (IC(50) values from 0.26 to 43 μM). Functional studies on prostate adenocarcinoma cells revealed that pyrogallol and protocatechuic acid specifically antagonized ephrinA1-Fc-induced EphA2 phosphorylation at concentrations that were not cytotoxic. The active concentrations of pyrogallol appear to be close to what can be reached in vivo under physiological conditions. Finally, because of the roles played by the Eph-ephrin system not only in cancer development but also in neurodegeneration and diabetes, pyrogallol and protocatechuic acid are candidates for more detailed functional studies to elucidate their role in these pathophysiological processes.

Resveratrol treatment reduces cardiac progenitor cell dysfunction and prevents morpho-functional ventricular remodeling in type-1 diabetic rats

Emerging evidence suggests that both adult cardiac cell and the cardiac stem/progenitor cell (CSPC) compartments are involved in the patho-physiology of diabetic cardiomyopathy (DCM). We evaluated whether early administration of Resveratrol, a natural antioxidant polyphenolic compound, in addition to improving cardiomyocyte function, exerts a protective role on (i) the progenitor cell pool, and (ii) the myocardial environment and its impact on CSPCs, positively interfering with the onset of DCM phenotype. Adult Wistar rats (n = 128) with streptozotocin-induced type-1 diabetes were either untreated (D group; n = 54) or subjected to administration of trans-Resveratrol (i.p. injection: 2.5 mg/Kg/day; DR group; n = 64). Twenty-five rats constituted the control group (C). After 1, 3 or 8 weeks of hyperglycemia, we evaluated cardiac hemodynamic performance, and cardiomyocyte contractile properties and intracellular calcium dynamics. Myocardial remodeling and tissue inflammation were also assessed by morphometry, immunohistochemistry and immunoblotting. Eventually, the impact of the diabetic “milieu” on CSPC turnover was analyzed in co-cultures of healthy CSPCs and cardiomyocytes isolated from D and DR diabetic hearts. In untreated animals, cardiac function was maintained during the first 3 weeks of hyperglycemia, although a definite ventricular remodeling was already present, mainly characterized by a marked loss of CSPCs and adult cardiac cells. Relevant signs of ventricular dysfunction appeared after 8 weeks of diabetes, and included: 1) a significant reduction in ±dP/dt in comparison with C group, 2) a prolongation of isovolumic contraction/relaxation times, 3) an impaired contraction of isolated cardiomyocytes associated with altered intracellular calcium dynamics. Resveratrol administration reduced atrial CSPC loss, succeeded in preserving the functional abilities of CSPCs and mature cardiac cells, improved cardiac environment by reducing inflammatory state and decreased unfavorable ventricular remodeling of the diabetic heart, leading to a marked recovery of ventricular function. These findings indicate that RSV can constitute an adjuvant therapeutic option in DCM prevention.

Identification of microbial metabolites derived from in vitro fecal fermentation of different polyphenolic food sources

OBJECTIVE

The biological effects of dietary polyphenols are linked to their bioavailability and catabolism in humans. The colon, with its symbiotic microbiota, is an active site where complex polyphenolic compounds are possibly modified to smaller and more absorbable molecules. The aim of this study was to identify the major metabolites derived from microbial colonic fermentation of some common polyphenol-rich foods.

METHODS

An in vitro fecal fermentation model was applied to 16 polyphenol-rich foods and polyphenolic precursors. Phenolic metabolites were identified by high-performance liquid chromatography coupled with tandem mass spectrometric detection.

RESULTS

Twenty-four phenolic fermentation metabolites were characterized. Some metabolites were common to several polyphenol-rich foods, whereas others were characteristic of specific sources.

CONCLUSION

The metabolites identified in vitro likely are generated in the human colon after consumption of polyphenol-rich foods. Their occurrence in plasma and/or urine should be considered when evaluating the bioavailability of polyphenols from specific food groups in humans and in the definition of markers of exposure to specific foods or food groups in epidemiologic studies. However, the search for these and other microbial metabolites after a feeding study in vivo should consider their possible further conjugation at the level of the liver.

Antioxidant capacity and angiotensin I converting enzyme inhibitory activity of a melon concentrate rich in superoxide dismutase

Antioxidant capacity and angiotensin 1-converting enzyme (ACE) inhibitory activity of a melon concentrate rich in superoxide dismutase (SOD-MC) were investigated in vitro. The total antioxidant capacity (TAC) was measured by the Trolox equivalent antioxidant capacity assay (TEAC), the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay, and the ferric reducing antioxidant power assay (FRAP). The ability of the extract to scavenge three specific reactive oxygen species (superoxide radical anion (O(2)(-)), hydroxyl radical (HO()) and hydrogen peroxide (H(2)O(2))) was also investigated in order to better evaluate its antioxidant properties. Even if the measures of TAC were relatively low, results clearly established an antioxidant potential of SOD-MC that exhibited the highest radical-scavenging activity towards O(2)(-), with a IC(50) 12-fold lower than that of H(2)O(2) or HO(). This lets hypothesis that the antioxidant potential of SOD-MC could be mainly due to its high level of SOD. Moreover, for the first time, an ACE inhibitory activity of SOD-MC (IC(50)=2.4±0.1mg/mL) was demonstrated, showing that its use as a functional food ingredient with potential preventive benefits in the context of hypertension may have important public health implications and should be carefully considered.

Updated bioavailability and 48 h excretion profile of flavan-3-ols from green tea in humans

Green tea is a popular beverage, prepared with infusion of unfermented dried leaves of Camellia sinensis, and is one of the most relevant sources of polyphenolic compounds in the human diet. This study reports green tea flavan-3-ol absorption, metabolism and complete urinary excretion up to 48 h in 20 healthy volunteers. Urinary and tea samples were analysed by high-performance liquid chromatography coupled with tandem mass spectrometry. Green tea contained monomeric flavan-3-ols and proanthocyanidins with a total polyphenol content of 728 μmol. A total of 41 metabolites were identified in urines, all present in conjugated forms. Among these, six colonic metabolites of green tea flavan-3-ols were identified for the first time after green tea consumption in humans. The average 48 h bioavailability was close to 62%, major contributors being microbial metabolites. Some volunteer showed a 100% absorption/excretion, whereas some others were unable to efficiently absorb/excrete this class of flavonoids. This suggests that colonic ring fission metabolism could be relevant in the putative bioactivity of green tea polyphenols.

Polyphenolic composition of hazelnut skin

Skins from different hazelnut samples were characterized for total polyphenol content, total antioxidant capacity (TAC), and their content in specific polyphenolic compounds. The main polyphenolic subclass, identified and quantified by means of HPLC-MS/MS, comprised monomeric and oligomeric flavan-3-ols, which accounted for more than 95% of total polyphenols. Flavonols and dihydrochalcones were 3.5% while phenolic acids were less than 1% of the total identified phenolics. The TAC values of the skin samples ranged between 0.6 and 2.2 mol of reduced iron/kg of sample, which is about 3 times the TAC of whole walnuts, 7-8 times that of dark chocolate, 10 times that of espresso coffee, and 25 times that of blackberries. By describing the profile of polyphenols present in hazelnut skins, this study provides the basis to further investigate the potential health effects of hazelnut byproduct.

Total antioxidant capacity of the diet is associated with lower risk of ischemic stroke in a large Italian cohort

Experimental studies suggest that oxidative stress and systemic inflammation are involved in the pathogenesis of ischemic stroke. Consuming a diet with a high total antioxidant capacity (TAC) has been related to reduced inflammation and increased circulating antioxidants in cross-sectional and randomized intervention studies. This study investigates the relation between dietary TAC and risk of ischemic and hemorrhagic stroke in 41,620 men and women not previously diagnosed with stroke or myocardial infarction, representing the Italian segment of the European Prospective Investigation into Cancer and Nutrition. Controlling for potential confounders, a diet rich in TAC was associated with a reduction in HR for all types of stroke, but this association was only marginally significant (P-trend = 0.054). When only ischemic stroke cases were considered, data suggest a stronger inverse association with dietary TAC, with HR = 0.41 (95% CI = 0.23-0.74). Regarding single antioxidants, data from subanalyses on stroke types suggest that vitamin C is significantly associated with a decreased risk of ischemic stroke [HR = 0.58 (95% CI = 0.34-0.99)], whereas vitamin E was associated with increased HR of hemorrhagic stroke in the highest tertile of intake [HR = 2.94 (95% CI = 1.13-7.62)]. In conclusion, our findings suggest that antioxidants may play a role in reducing the risk of cerebral infarction but not hemorrhagic stroke. However, a high intake of vitamin E could be positively associated to the risk of brain hemorrhagic events; therefore, more focused investigations about this observation are needed.

Bioavailability of dietary flavonoids and phenolic compounds

This paper reviews recent human studies on the bioavailability of dietary flavonoids and related compounds, including chlorogenic acids and ellagitannins, in which the identification of metabolites, catabolites and parent compounds in plasma, urine and ileal fluid was based on mass spectrometric methodology. Compounds absorbed in the small intestine appear in the circulatory system predominantly as glucuronide, sulfate and methylated metabolites which seemingly are treated by the body as xenobiotics as they are rapidly removed from the bloodstream. As a consequence, while analysis of plasma provides valuable information on the identity and pharmacokinetic profiles of circulating metabolites after acute supplementation, it does not provide accurate quantitative assessments of uptake from the gastrointestinal tract. Urinary excretion, of which there are great variations with different classes of flavonoids, provides a more realistic figure but, as this does not include the possibility of metabolites being sequestered in body tissues, this too is an under estimate of absorption, but to what degree remains to be determined. Even when absorption occurs in the small intestine, feeding studies with ileostomists reveal that substantial amounts of the parent compounds and some of their metabolites appear in ileal fluid indicating that in volunteers with a functioning colon these compounds will pass to the large intestine where they are subjected to the action of the colonic microflora. A diversity of colonic-derived catabolites is absorbed into the bloodstream and passes through the body prior to excretion in urine. There is growing evidence that these compounds, which were little investigated until recently, are produced in quantity in the colon and form a key part of the bioavailability equation of dietary flavonoids and related phenolic compounds.

Bioavailability of coffee chlorogenic acids and green tea flavan-3-ols

This paper reviews recent human studies on the bioavailability of chlorogenic acids in coffee and green tea flavan-3-ols in which the identification of metabolites, catabolites and parent compounds in plasma, urine and ileal fluid was based on mass spectrometric methodology. Both the chlorogenic acids and the flavan-3-ols are absorbed in the small intestine and appear in the circulatory system predominantly as glucuronide, sulfate and methylated metabolites. Even when absorption occurs in the small intestine, feeding studies with ileostomists reveal that substantial amounts of the parent compounds and some of their metabolites appear in ileal fluid indicating that in volunteers with a functioning colon these compounds will pass to the large intestine where they are subjected to the action of the colonic microflora. A diversity of colonic-derived catabolites are absorbed into the bloodstream and pass through the body prior to excretion in urine. There is growing evidence that these compounds, which were little investigated until recently, are produced in quantity in the colon and form a key part of the bioavailability equation of flavonoids and related compounds that occur in fruits, vegetables and beverages. Recent evidence indicates that some colon-derived phenolic acids have in vitro anti-inflammatory activity.

Bioavailability of catechins from ready-to-drink tea

OBJECTIVE

Because consumption of teas may be associated with potential health benefits due to its content in polyphenols and in Western countries the consumption of tea is equally divided between the hot and the ready-to-drink (RTD) cold versions of this typical beverage, the aim of this work was to study the absorption and metabolism of flavan-3-ols in human volunteers after the ingestion of a commercial RTD tea.

METHODS

A feeding study was carried out in 20 healthy human volunteers and urine samples were collected for 24h after tea ingestion. Flavan-3-ols-derived molecules were identified and quantified in urine samples by high-performance liquid chromatography with tandem mass spectrometric detection.

RESULTS

Eight relevant metabolites were identified in urine, all modified flavan-3-ols with the exception of unmetabolized gallic acid. The urinary excretion of flavan-3-ols was equal to 7.2% of the intake with tea. Gallic acid, which was abundant in the RTD tea used in this study, reached a 4.5% of the drunken amount.

CONCLUSIONS

The bioavailability values observed are in agreement with previous reports, although the dosage of polyphenols ingested in this study is remarkably lower. Moreover, the use of a group of 20 volunteers, more than the average number of subjects used for usual human acute-feeding studies involving polyphenols, provides additional credibility to the results. After drinking the RTD ice tea used in this study, the internal compartments are exposed to non-marginal doses of flavanols and flavanol metabolites up to 24h.

Effect of domestic cooking methods on the total antioxidant capacity of vegetables

As well as tables of food composition, total antioxidant capacity (TAC) databases--developed in past years for investigating health effects of antioxidant-rich foods in epidemiological and nutritional studies--have been created on the basis of analytical data from raw plant material. However, most vegetables are commonly cooked before consumption. With the aim of completing a previously developed TAC database, the effect of the major domestic practices (i.e. boiling, pan-frying and deep-frying) on the TAC of commonly consumed cooked vegetables was evaluated. Based on dry weight, boiling generally resulted in positive TAC changes whereas a general negative effect on the TAC was observed in pan-fried vegetables. Deep-frying produced a TAC increase of potato, artichoke and aubergine but a TAC reduction of mushroom and onion. The present study clearly indicates that cooking is not always a detrimental process when the TAC is used as an index to evaluate the nutritional characteristics of vegetables.

Food selection based on total antioxidant capacity can modify antioxidant intake, systemic inflammation, and liver function without altering markers of oxidative stress

BACKGROUND

It is unknown whether diets with a high dietary total antioxidant capacity (TAC) can modify oxidative stress, low-grade inflammation, or liver dysfunction, all of which are risk factors for type 2 diabetes and cardiovascular disease.

OBJECTIVE

We studied the effect of high- and low-TAC (HT and LT, respectively) diets on markers of antioxidant status, systemic inflammation, and liver dysfunction.

DESIGN

In a crossover intervention, 33 healthy adults (19 men, 14 women) received the HT and LT diets for 2 wk each. Dietary habits were checked with a 3-d food record during both diet periods and the washout period.

RESULTS

Fruit and vegetable, macronutrient, dietary fiber, and alcohol intakes did not differ significantly between the 2 diets, whereas dietary TAC, alpha-tocopherol, and ascorbic acid were significantly (P < 0.001) higher during the HT diet. Plasma alpha-tocopherol rose during the HT and decreased during the LT diet (P < 0.02 for difference) without changes in markers of oxidative stress except plasma malondialdehyde, which decreased unexpectedly during the LT diet (P < 0.05). Plasma high-sensitivity C-reactive protein, alanine aminotransferase, gamma-glutamyltranspeptidase, and alkaline phosphatase concentrations decreased during the HT compared with the LT diet (mean +/- SEM for pre-post changes: -0.72 +/- 0.37 compared with 1.05 +/- 0.60 mg/L, P < 0.01; -1.73 +/- 1.02 compared with 2.33 +/- 2.58 U/L, P < 0.01; -2.12 +/- 1.45 compared with 5.15 +/- 2.98 U/L, P < 0.05; and 1.36 +/- 1.34 compared with 5.06 +/- 2.00 U/L, P < 0.01, respectively).

CONCLUSION

Selecting foods according to their TAC markedly affects antioxidant intake and modulates hepatic contribution to systemic inflammation without affecting traditional markers of antioxidant status.

Phytochemical profile of main antioxidants in different fractions of purple and blue wheat, and black barley

Two pigmented wheat genotypes (blue and purple) and two black barley genotypes were fractionated in bran and flour fractions, examined, and compared for their free radical scavenging properties against 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (Trolox equivalent antioxidant capacity, TEAC), ferric reducing antioxidant power (FRAP), total phenolic content (TPC), phenolic acid composition, carotenoid composition, and total anthocyanin content. The results showed that fractionation has a significant influence on the antioxidant properties, TPC, anthocyanin and carotenoid contents, and phenolic acid composition. Bran fractions had the greatest antioxidant activities (1.9-2.3 mmol TEAC/100 g) in all four grain genotypes and were 3-5-fold higher than the respective flour fractions (0.4-0.7 mmol TEAC/100 g). Ferulic acid was the predominant phenolic acid in wheat genotypes (bran fractions) while p-coumaric acid was the predominant phenolic acid in the bran fractions of barley genotypes. High-performance liquid chromatography analysis detected the presence of lutein and zeaxanthin in all fractions with different distribution patterns within the genotypes. The highest contents of anthocyanins were found in the middlings of black barley genotypes or in the shorts of blue and purple wheat. These data suggest the possibility to improve the antioxidant release from cereal-based food through selection of postharvest treatments.

Total antioxidant capacity of the diet is inversely and independently related to plasma concentration of high-sensitivity C-reactive protein in adult Italian subjects

Inflammation, a risk factor for cardiovascular disease, is associated with low plasma levels of antioxidant vitamins. In addition to vitamins, other antioxidants modulate the synthesis of inflammatory markers in vitro and contribute to the total antioxidant capacity (TAC) of a diet. However, the relationship between dietary TAC and markers of inflammation has never been evaluated in vivo. We investigated the relationship between dietary TAC and markers of systemic (high-sensitivity C-reactive protein (hs-CRP), leucocytes) and vascular (soluble intercellular cell adhesion molecule-1) inflammation in 243 non-diabetic subjects. General Linear Model (GLM) analysis showed a significant (P=0·005) inverse relationship between hs-CRP and quartiles of energy-adjusted dietary TAC, even when recognized modulating factors of inflammation, namely alcohol, fibre, vitamin C, α-tocopherol, β-carotene, BMI, waist circumference, HDL-cholesterol, hypertension, insulin sensitivity and plasma β-carotene, were included in the model as covariates (P=0·004). The relationship was stronger for subjects with hypertension (P=0·013 v. P=0·109 for normotensive individuals). Among dietary factors, TAC was significantly higher (5·3 (sd 3·0) v. 4·9 (sd 2·7) mmol Trolox/d; P=0·026) in subjects with low plasma hs-CRP (range: 0·0–4·1 mg/l) than in subjects with high plasma hs-CRP (range: 4·2–27·8 mg/l). We conclude that dietary TAC is inversely and independently correlated with plasma concentrations of hs-CRP and this could be one of the mechanisms explaining the protective effects against CVD of antioxidant-rich foods such as fruits, whole cereals and red wine. This could be of particular significance for subjects with high blood pressure.

Development and validation of a food frequency questionnaire for the assessment of dietary total antioxidant capacity

The total antioxidant capacity (TAC) of the diet may be an important tool to monitor the protective effect of plant foods in epidemiological studies. We developed a semi-quantitative FFQ for the assessment of dietary TAC by 3 different assays, i.e., Trolox equivalent antioxidant capacity (TEAC), total radical-trapping antioxidant parameter (TRAP) and ferric reducing-antioxidant power (FRAP). The FFQ consists of 53 questions about the major sources of dietary TAC in Northern Italy and was validated against a 3-d weighed food record (3D-WR) in 285 individuals (159 males and 126 females) aged 35-88 y and living in the province of Parma (Italy). Plasma TAC was also evaluated in a subgroup of subjects using the TEAC and FRAP assays. The FFQ was associated with 3D-WR (quadratic-weighted kappa = 0.49 for TEAC, 0.53 for TRAP, and 0.49 for FRAP; P < 0.0001) and proved reasonably accurate to classify individuals into quartiles of TAC intake. The FFQ had a good repeatability when readministered after 1 y in 55 subjects (quadratic-weighted kappa for intertertile agreement = 0.66 for TEAC, 0.70 for TRAP and 0.68 for FRAP; P < 0.0001). With both dietary instruments, the main contributors to TAC intake were coffee and tea in women and alcoholic beverages in men, followed by fruits and vegetables in both sexes. Plasma TAC and dietary TAC were not associated. In conclusion, our FFQ has the potential for being used to rank subjects on the basis of their antioxidant intake as determined by dietary TAC in large epidemiological studies. The FFQ should be validated in external populations before being used for research purposes.

Total antioxidant capacity of spices, dried fruits, nuts, pulses, cereals and sweets consumed in Italy assessed by three different in vitro assays

With the aim to expand the Italian total antioxidant capacity (TAC) database, the TAC values of 11 spices, 5 dried fruits, 7 sweets, 18 cereal products, 5 pulses, and 6 nuts were determined using three different assays and considering the contribution of bound antioxidant compounds in fiber-rich foods (i. e. cereals, legumes, and nuts). Among spices, saffron displayed the highest antioxidant capacity, whereas among dried fruits, prune exhibited the highest value. The TAC values of all the chocolates analyzed were far higher than the other sweet extracts measured. Among cereal products, whole meal buckwheat and wheat bran had the greatest TAC. Among pulses and nuts, broad bean, lentil and walnuts had the highest antioxidant capacity, whereas chickpeas, pine nuts and peanuts were less effective. The contribution of bound phytochemicals to the overall TAC was relevant in cereals as well as in nuts and pulses. The complete TAC database could be utilized to properly investigate the role of dietary antioxidants in disease prevention.

Dietary glycemic index and liver steatosis

BACKGROUND

Insulin resistance (IR) and liver steatosis (LS) are interlinked metabolic derangements whose prevalence is rapidly increasing, but the effect of dietary carbohydrate quality on LS is unknown.

OBJECTIVE

The objective was to describe the relation of IR and LS to total carbohydrate, total dietary fiber, and the glycemic index (GI) and glycemic load of the diet.

DESIGN

The study was a cross-sectional evaluation of 247 apparently healthy subjects who had no evidence of viral, toxic, or autoimmune hepatitis and who were unselected for alcohol intake. The homeostasis model assessment index was used as a surrogate measure of IR, and a liver echography was used as a proxy for LS grading. Dietary data were collected by using 3-d food records. Total carbohydrate intake, total dietary fiber, GI, and glycemic load were calculated by using a semiquantitative food-frequency questionnaire concerning the dietary sources of carbohydrates.

RESULTS

The prevalence of high-grade LS (HG-LS) increased significantly across quartiles of dietary GI (P for trend < 0.034): HG-LS in the 4th quartile (high GI) was twice that in the first 3 quartiles (low to medium GIs), whereas no relation was observed with total carbohydrates, total dietary fiber, or glycemic load. In insulin-sensitive subjects (first 3 quartiles of homeostasis model assessment index of IR), the prevalence of HG-LS did not differ significantly between GI groups, but, in insulin-resistant subjects (4th quartile of homeostasis model assessment index of IR), it was twice as high in those with high GI as in those with low to medium GIs (P = 0.005).

CONCLUSIONS

High-GI dietary habits are associated with HG-LS, particularly in insulin-resistant subjects. Dietary advice on the quality of carbohydrate sources therefore may be a complementary tool for preventing or treating LS of metabolic origin.

Total antioxidant capacity of cerebrospinal fluid is decreased in patients with motor neuron disease

Oxidative stress has been associated with motor neuron disease (MND). The human body has several antioxidant defense systems to repair the damage caused by oxidative stress. The activity of these systems is thought to be reduced in neurodegenerative diseases, which may increase the level of oxidative damage and be a contributing factor to motor neuron death. In the present study, we compared the total antioxidant capacity (TAC) of human serum and cerebrospinal fluid (CSF) of MND patients with that of a control group including patients with migraine, tension headache and psychiatric disorders. Within-subject serum and CSF TAC were strongly correlated (r=0.639; p=0.000), and CSF TAC was significantly lower in MND patients as compared to controls after adjustment for known influencing factors (112.7 micromol Fe/L+/-11.7 versus 135.2 micromol Fe/L+/-19.7; p=0.012). No differences in serum or CSF TAC were observed among the clinical forms of MND considered in this work. In conclusion, the CSF TAC was strongly correlated with serum TAC, and a decrease in CSF TAC was demonstrated in MND patients compared to controls that was not independent from serum antioxidants, this translating in a systemic (but prevailing in the CNS) oxidative damage in this pathology.

Colonic fermentation of indigestible carbohydrates contributes to the second-meal effect

BACKGROUND

Low postprandial blood glucose is associated with low risk of metabolic diseases. A meal's ability to diminish the glucose response to carbohydrates eaten during the following meal is known as the "second-meal effect" (SME). The reduced glycemia elicited by low-glycemic-index (LGI) foods consumed during the first meal has been suggested as the main mechanism for SME. However, LGI foods often increase colonic fermentation because of the presence of fiber and resistant starch.

OBJECTIVE

The objective was to study the SME of greater fermentation of high-glycemic-index (HGI) and LGI carbohydrates eaten during a previous meal.

DESIGN

Ten healthy volunteers ate 3 breakfast test meals consisting of sponge cakes made with rapidly digestible, nonfermentable amylopectin starch plus cellulose (HGI meal), amylopectin starch plus the fermentable disaccharide lactulose (HGI-Lac meal), or slowly digestible, partly fermentable amylose starch plus cellulose (LGI meal). Five hours later, subjects were fed the same standard lunch containing 93 g available carbohydrates. Blood was collected for measurement of glucose, insulin, and nonesterified fatty acids (NEFAs). Breath hydrogen was measured as a marker of colonic fermentation. Postlunch gastric emptying was measured by using ultrasonography.

RESULTS

Both the HGI-Lac and LGI meals improved glucose tolerance at lunch. In the case of the HGI-Lac meal, this effect was concomitant with low NEFA concentrations and delayed gastric emptying.

CONCLUSION

Fermentable carbohydrates, independent of their effect on a food's glycemic index, have the potential to regulate postprandial responses to a second meal by reducing NEFA competition for glucose disposal and, to a minor extent, by affecting intestinal motility.

Antioxidant characterization of some Sicilian edible wild greens

Epidemiological studies have demonstrated that many antioxidants and the total antioxidant capacity (TAC) of the diet may protect against cancers and cardiovascular disease. Common fruits and vegetables are good sources of antioxidants, although in some Mediterranean areas traditional wild greens are responsible for a significant percentage of total dietary antioxidant intake. In the European Prospective Investigation into Cancer and Nutrition cohort of Ragusa (Sicily), a high number of subjects were found to frequently eat wild greens, including Sinapis incana and Sinapis nigra, Diplotaxis erucoides, Cichorium intybus, Asparagus acutifolius, and Borrago officinalis. On the basis of these observations, detailed characterization of single antioxidant components (i.e., polyphenols, carotenoids, chlorophylls, and ascorbic acid) and the TAC of these edible wild traditional plants was performed. The wild plants examined were found to be very rich in antioxidants, such as flavonoids and carotenoids, with high TAC values, suggesting that the importance of these vegetables, not only in the traditional but even in the contemporary diet, needs to be emphasized.

A review of recent studies on malondialdehyde as toxic molecule and biological marker of oxidative stress

AIM

Of the many biological targets of oxidative stress, lipids are the most involved class of biomolecules. Lipid oxidation gives rise to a number of secondary products. Malondialdehyde (MDA) is the principal and most studied product of polyunsaturated fatty acid peroxidation. This aldehyde is a highly toxic molecule and should be considered as more than just a marker of lipid peroxidation. Its interaction with DNA and proteins has often been referred to as potentially mutagenic and atherogenic. This review is intended to briefly describe the physiological origin of MDA, to highlight its toxicity, describe and comment on the most recent methods of detection and discuss its occurrence and significance in pathology.

DATA SYNTHESIS

In vivo origin as well as reactivity and consequent toxicity of MDA are reviewed. The most recent and improved procedures for the evaluation of MDA in biological fluids are described and discussed. The evidence of the occurrence of increased MDA levels in pathology is described.

CONCLUSIONS

In the assessment of MDA, the most common methods of detection are insufficiently sensitive and disturbed by interference coming from related species or overestimation derived from stressing analysis conditions. Moreover, no recent nutritional or medical trials report the use of one of the new and more reliable methods, some of which are undoubtedly accessible to virtually all the laboratories provided with a common HPLC or a spectrofluorimeter.

Understanding the association between dietary antioxidants, redox status and disease: is the Total Antioxidant Capacity the right tool?

Total Antioxidant Capacity (TAC) considers the cumulative action of all the antioxidants present in plasma and body fluids, thus providing an integrated parameter rather than the simple sum of measurable antioxidants. The capacity of known and unknown antioxidants and their synergistic interaction is, therefore, assessed, thus giving an insight into the delicate balance in vivo between oxidants and antioxidants. There is new evidence indicating the importance of understanding the mechanisms of the homeostatic control of TAC in plasma and tissues and its modification during oxidative stress development. Recently, the epidemiological application of TAC has been proposed as a new tool for investigating the relationship between dietary antioxidants and cancer risk in population studies. This review outlines the pros and cons of the more common assays for measuring plasma TAC and the latest findings on dietary modulation of plasma redox status. Finally, the feasibility of the 'TAC concept' as an innovative tool for investigating the association between diet and oxidative stress is discussed.