No abstract

Background: There are very limited data regarding the effects of blueberry flavonoid intake on vascular function in healthy humans. Objectives: We investigated the impact of blueberry flavonoid intake on endothelial function in healthy men and assessed potential mechanisms of action by the assessment of circulating metabolites and neutrophil NADPH oxidase activity. Design: Two randomized, controlled, double-blind, crossover humanintervention trials were conducted with 21 healthy men. Initially, the impact of blueberry flavonoid intake on flow-mediated dilation (FMD) and polyphenol absorption and metabolism was assessed at baseline and 1, 2, 4, and 6 h after consumption of blueberry containing 766, 1278, and 1791 mg total blueberry polyphenols or a macronutrientand micronutrient-matched control drink (0 mg total blueberry polyphenols). Second, an intake-dependence study was conducted (from baseline to 1 h) with 319, 637, 766, 1278, and 1791 mg total blueberry polyphenols and a control. Results: We observed a biphasic time-dependent increase in FMD, with significant increases at 1-2 and 6 h after consumption of blueberry polyphenols. No significant intake-dependence was observed between 766 and 1791 mg. However, at 1 h after consumption, FMD increased dose dependently to #766 mg total blueberry polyphenol intake, after which FMD plateaued. Increases in FMD were closely linked to increases in circulating metabolites and by decreases in neutrophil NADPH oxidase activity at 1-2 and 6 h. Conclusions: Blueberry intake acutely improves vascular function in healthy men in a time-and intake-dependent manner. These benefits may be mechanistically linked to the actions of circulating phenolic metabolites on neutrophil NADPH oxidase activity. This trial was registered at clinicaltrials.gov as NCT01292954 and NCT01829542.Am J Clin Nutr 2013;98:1179-91.

This study shows, for the first time to our knowledge, that consumption of cocoa flavanols can significantly affect the growth of select gut microflora in humans, which suggests the potential prebiotic benefits associated with the dietary inclusion of flavanol-rich foods. This trial was registered at clinicaltrials.gov as NCT01091922.

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We have investigated the bacterial-dependent metabolism of (2 )-epicatechin and (þ )-catechin using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal region of the human large intestine. Incubation of (2)-epicatechin or (þ )-catechin (150 mg/l or 1000 mg/l) with faecal bacteria, led to the generation of 5-(3 0 ,4 0 -dihydroxyphenyl)-g-valerolactone, 5-phenyl-g-valerolactone and phenylpropionic acid. However, the formation of these metabolites from (þ )-catechin required its initial conversion to (þ )-epicatechin. The metabolism of both flavanols occurred in the presence of favourable carbon sources, notably sucrose and the prebiotic fructo-oligosaccharides, indicating that bacterial utilisation of flavanols also occurs when preferential energy sources are available. (þ )-Catechin incubation affected the growth of select microflora, resulting in a statistically significant increase in the growth of the Clostridium coccoides -Eubacterium rectale group, Bifidobacterium spp. and Escherichia coli, as well as a significant inhibitory effect on the growth of the C. histolyticum group. In contrast, the effect of (2)-epicatechin was less profound, only significantly increasing the growth of the C. coccoides -Eubacterium rectale group. These potential prebiotic effects for both (þ )-catechin and (2 )-epicatechin were most notable at the lower concentration of 150 mg/l. As both (2)-epicatechin and (þ )-catechin were converted to the same metabolites, the more dramatic change in the growth of distinct microfloral populations produced by (þ )-catechin incubation may be linked to the bacterial conversion of (þ )-catechin to (þ)-epicatechin. Together these data suggest that the consumption of flavanol-rich foods may support gut health through their ability to exert prebiotic actions. Flavanols: Prebiotics: Faecal microflora: Large intestineRepresenting one of the most important lifestyle factors, diet can strongly influence the incidence and onset of CVD (1) , and thus a healthy diet is an essential factor for healthy ageing (2) . A number of dietary intervention studies in human subjects and animals, in particular those using Vitis vinifera (grape), Camellia sinensis (tea) and Theobroma cacao (cocoa) have demonstrated beneficial effects on vascular function (3 -5) . While such foods and beverages differ greatly in chemical composition and macro-and micronutrient content, they have in common that they are amongst the major dietary sources of flavanols. The in vivo effects of flavanols will be dependent on the absorption and metabolism of flavanols in the gastrointestinal tract. Studies have indicated that flavanols are subject to extensive metabolism by phase I and II enzymes to yield O-methylated, sulfated and glucuronidated forms during transfer from the small-intestinal lumen to the portal blood (6) . However, significant amounts of ingested (2 )-epicatechin, (þ)-catechin, and their structurally related oligomeric forms (procyanidins), escape absorption in the small intestine, instead rea...

Oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) and dopamine (DA) to generate semiquinones/ quinones, oxygen radicals, and other reactive oxygen species may play a role in neuronal cell death in Parkinson's disease (PD). In particular, semiquinones/quinones can form conjugates with thiol compounds such as GSH and cysteine. Exposure of L-DOPA, DA, and other catecholamines to a system generating O2 radical led to O 2~-dependent depletion of added GSH (or cysteine), accompanied by the formation of thiol-DA or -DOPA adducts as detected by HPLC. Superoxide could additionally cause destruction of these adducts. Iron or copper ions could also promote conjugate formation between GSH or cysteine and DA and L-DOPA, especially if H202 was present. We applied HPLC to measure glutathionyl and cysteinyl conjugates of L-DOPA, DA, and 3,4-dihydroxyphenylacetic acid (DOPAC) in postmortem brain samples from PD patients and normal control subjects. Conjugates were detected in most brain areas examined, but levels were highest in the substantia nigra and putamen. In most regions, adduct levels were lower in PD, but there were significant increases in cysteinyl adducts of L-DOPA, DA, and DOPAC in PD substantia nigra, suggesting that acceleration of L-DOPA/DA oxidation occurs in PD, although we cannot say if this is a primary feature of the disease or if it is related to therapy with L-DOPA. In vitro, conjugate formation could be inhibited by the dithiol dihydrolipoate but not by its oxidised form, lipoic acid. Key Words: L-3,4-Dihydroxyphenylalanine-Parkinson's disease-Superoxide-5-S-Cysteinyldopamine-5-S -Cysteinyl -3,4-dihydroxyphenylalanine-Oxidative stress-a-Lipoate.

We have studied the perfusion of the jejunum and ileum in an isolated rat intestine model with flavonoids and hydroxycinnamates and the influence of glycosylation on the subsequent metabolism. Flavone and flavonol glucosides and their corresponding aglycones are glucuronidated during transfer across the rat jejunum and ileum and this glucuronidation occurs without the need for gut microflora. Furthermore, this suggests the presence of glycosidases as well as UDP-glucuronyl transferase in the jejunum. In contrast, quercetin-3-glucoside and rutin are mainly absorbed unmetabolised. The results suggest that the more highly reducing phenolics are absorbed predominantly as glucuronides (96.5% þ 4.6) of the amount absorbed, whereas monophenolic hydroxycinnamates and monophenolic Bring flavonoids are less predisposed to glucuronidation and higher levels of aglycone (88.1% þ 10.1) are detected on absorption through both the jejunum and ileum.z 1999 Federation of European Biochemical Societies.

We have conducted a detailed investigation into the absorption, metabolism and microflora-dependent transformation of hydroxytyrosol (HT), tyrosol (TYR) and their conjugated forms, such as oleuropein (OL). Conjugated forms underwent rapid hydrolysis under gastric conditions, resulting in significant increases in the amount of free HT and TYR entering the small intestine. Both HT and TYR transferred across human Caco-2 cell monolayers and rat segments of jejunum and ileum and were subject to classic phase I/II biotransformation. The major metabolites identified were an O-methylated derivative of HT, glucuronides of HT and TYR and a novel glutathionylated conjugate of HT. In contrast, there was no absorption of OL in either model. However, OL was rapidly degraded by the colonic microflora resulting in the formation of HT. Our study provides additional information regarding the breakdown of complex olive oil polyphenols in the GI tract, in particular the stomach and the large intestine.