Dibenzoate esters of cis-tetralin-2,3-diol as analogs of (-)-epigallocatechin gallate: synthesis and crystal structure of anticancer drug candidates.

(-)-Epigallocatechin gallate (EGCG), the main component of green tea extract, displays multiple biological activities. However, it cannot be used as a drug due to its low cellular absorption, instability and metabolic degradation. Therefore, there is a need to provide analogs that can overcome the limitations of EGCG. In this work, six synthetic analogs of EGCG sharing a common tetralindiol dibenzoate core were synthesized and fully characterized by 1H NMR, 13C NMR, HRMS and IR spectroscopies, and X-ray crystallography. These are (2R,3S)-1,2,3,4-tetrahydronaphthalene-2,3-diyl bis[3,4,5-tris(benzyloxy)benzoate], C66H56O10, and the analogous esters bis(3,4,5-trimethoxybenzoate), C30H32O10, bis(3,4,5-trifluorobenzoate), C24H14F6O4, bis[4-(benzyloxy)benzoate], C38H32O6, bis(4-methoxybenzoate), C26H24O6, and bis(2,4,6-trifluorobenzoate), C24H14F6O4. Structural analysis revealed that the molecular shapes of these dibenzoate esters of tetralindiol are significantly different from that of previously reported dimandelate esters or monobenzoate esters, as the acid moieties extend far from the bicyclic system without folding back over the tetralin fragment. Compounds with small fluorine substituents take a V-shape, whereas larger methoxy and benzyloxy groups determine the formation of an L-shape or a cavity. Intermolecular interactions are dominated by π-π stacking and C-H...π interactions involving the arene rings in the benzoate fragment and the arene ring in the tetrahydronaphthalene moiety. All six crystal structures are determined in centrosymmetric space groups (either P-1, P21/n, C2/c or I2/a).

Epigallocatechin-3-gallate Inhibits Cu(II)-Induced ß-2-Microglobulin Amyloid Formation by Binding to the Edge of Its ß-Sheets.

Epigallocatechin-3-gallate (EGCG) is a catechin found in green tea that can inhibit the amyloid formation of a wide variety of proteins. EGCG's ability to prevent or redirect the amyloid formation of so many proteins may reflect a common mechanism of action, and thus, greater molecular-level insight into how it exerts its effect could have broad implications. Here, we investigate the molecular details of EGCG's inhibition of the protein ß-2-microglobulin (ß2m), which forms amyloids in patients undergoing long-term dialysis treatment. Using size-exclusion chromatography and a collection of mass spectrometry-based techniques, we find that EGCG prevents Cu(II)-induced ß2m amyloid formation by diverting the normal progression of preamyloid oligomers toward the formation of spherical, redissolvable aggregates. EGCG exerts its effect by binding with a micromolar affinity (Kd ≈ 5 µM) to the ß2m monomer on the edge of two ß-sheets near the N-terminus. This interaction destabilizes the preamyloid dimer and prevents the formation of a tetramer species previously shown to be essential for Cu(II)-induced ß2m amyloid formation. EGCG's binding at the edge of the ß-sheets in ß2m is consistent with a previous hypothesis that EGCG generally prevents amyloid formation by binding cross-ß-sheet aggregation intermediates.

Methylomic correlates of autophagy activity in cystic fibrosis.

Autophagy is a highly regulated, biological process that provides energy during periods of stress and starvation. This conserved process also acts as a defense mechanism and clears microbes from the host cell. Autophagy is impaired in Cystic Fibrosis (CF) patients and CF mice, as their cells exhibit low expression levels of essential autophagy molecules. The genetic disorder in CF is due to mutations in the cystic fibrosis transmembrane conductance regulator (cftr) gene that encodes for a chloride channel. CF patients are particularly prone to infection by pathogens that are otherwise cleared by autophagy in healthy immune cells including Burkholderia cenocepacia (B. cenocepacia). The objective of this study is to determine the mechanism underlying weak autophagic activity in CF macrophages and find therapeutic targets to correct it. Using reduced representation bisulfite sequencing (RRBS) to determine DNA methylation profile, we found that the promoter regions of Atg12 in CF macrophages are significantly more methylated than in the wild-type (WT) immune cells, accompanied by low protein expression. The natural product epigallocatechin-3-gallate (EGCG) significantly reduced the methylation of Atg12 promoter improving its expression. Accordingly, EGCG restricted B. cenocepacia replication within CF mice and their derived macrophages by improving autophagy and preventing dissemination. In addition, EGCG improved the function of CFTR protein. Altogether, utilizing RRBS for the first time in the CF field revealed a previously unrecognized mechanism for reduced autophagic activity in CF. Our data also offers a mechanism by which EGCG exerts its positive effects in CF.

Effects of Lactobacillus salivarius WB21 combined with green tea catechins on dental caries, periodontitis, and oral malodor.

OBJECTIVE: To evaluate the combined use of Lactobacillus salivarius WB21 and (-)-epigallocatechin gallate (EGCg) for oral health maintenance. DESIGN: The effects of L. salivarius WB21 on growth of Streptococcus mutans, the insoluble glucan produced by S. mutans, and on growth of Porphyromonas gingivalis were evaluated in vitro. In addition, the susceptibility of five oral pathogenic bacteria and L. salivarius WB21 to EGCg, the inhibiting effect of EGCg on methyl mercaptan, and the effects of L. salivarius WB21 and EGCg in combination on growth of P. gingivalis were examined. RESULTS: Lactobacillus salivarius WB21 showed concentration-dependent inhibition of the growth of S. mutans. Addition of L. salivarius WB21 inhibited production of the insoluble glucan by S. mutans (p < 0.001). A filtrate of L. salivarius WB21 culture solution inhibited growth of P. gingivalis (p < 0.001 vs. control), and this effect was enhanced when it was used in combination with EGCg (p < 0.001 vs. the addition of L. salivarius WB21). In addition, EGCg directly inhibited methyl mercaptan in a concentration-dependent manner (p < 0.001). Concerning bacterial susceptibility to EGCg, growth of P. gingivalis, Prevotella intermedia, and Fusobacterium nucleatum was inhibited at 2.5 mg/mL of EGCg, while that of L. salivarius WB21 was inhibited at 25 mg/mL EGCg. CONCLUSIONS: Our results imply that L. salivarius WB21 may be useful for controlling dental caries, periodontitis, and oral malodor. In addition, the effects of L. salivarius WB21 on periodontitis and oral malodor may be synergistically enhanced by use in combination with EGCg.

Tas2r125 functions as the main receptor for detecting bitterness of tea catechins in the oral cavity of mice.

We attempted to identify mouse bitter taste receptors, Tas2rs, that respond to tea catechins. Among representative tea catechins, avoidance behavior of mice to (-)-epicatechin gallate (ECg) was the strongest, followed by (-)-epigallocatechin gallate (EGCg). Therefore, we measured ECg response using Tas2rs-expressing cells. Among the 35 members of Tas2r family, Tas2r108, 110, 113, 125, and 144 responded to ECg. Among these receptors, Tas2r113 and 125 also responded to EGCg. Because the response profiles of Tas2r125 were consistent with the results of the behavior assays, it was considered that Tas2r125 functions as the main receptor for detecting bitterness of tea catechins in the oral cavity. To determine the involvement of Tas2rs in the physiological action of catechins, mRNA expression of 5 Tas2rs was investigated in various tissues. Because mRNA expression of Tas2r108 was observed in some tissues including the gastrointestinal tract, it may be envisaged that Tas2r108 plays a part in exerting the physiological action of ECg. Tas2r125 expression was not observed in any of the tested tissues except the circumvallate papillae. Therefore, Tas2r125 was considered to mainly function in the events of catechin reception in the oral cavity.

Characterization and modulation of glucose uptake in a human blood-brain barrier model.

The blood-brain barrier (BBB) plays a key role in limiting and regulating glucose access to glial and neuronal cells. In this work glucose uptake on a human BBB cell model (the hCMEC/D3 cell line) was characterized. The influence of some hormones and diet components on glucose uptake was also studied. ³H-2-deoxy-D-glucose ([³H]-DG) uptake for hCMEC/D3 cells was evaluated in the presence or absence of tested compounds. [³H]-DG uptake was sodium- and energy-independent. [³H]-DG uptake was regulated by Ca²âº and calmodulin but not by MAPK kinase pathways. PKC, PKA and protein tyrosine kinase also seem to be involved in glucose uptake modulation. Progesterone and estrone were found to decrease ³H-DG uptake. Catechin and epicatechin did not have any effect, but their methylated metabolites increased [³H]-DG uptake. Quercetin and myricetin decreased [³H]-DG uptake, and glucuronic acid-conjugated quercetin did not have any effect. These cells expressed GLUT1, GLUT3 and SGLT1 mRNA.

Erythrocyte membrane transporters during human ageing: modulatory role of tea catechins.

Ageing is associated with many physiological and cellular changes, many of which are due to alterations in the plasma membrane. The functions of membrane transporter proteins are crucial for the maintenance of ionic homeostasis between the extra- and intracellular environments. The aim of the present study was to determine the status of erythrocyte membrane transporters, specifically Ca(2+) -ATPases, Na(+) /K(+) -ATPases and the Na(+) /H(+) exchanger (NHE), during ageing in humans. Furthermore, because tea catechins have been reported to possess strong anti-oxidant potential, the study was extended to evaluate the effect of (-)-epicatechin (EC), (-)-epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin-3-gallate (EGCG) on these transporters as a function of human age. The study was performed on 97 normal healthy subjects (62 men, 35 women; 16-80 years old). To investigate the effects of tea catechins, subjects were divided into three groups: young (<40 years old; n = 34); middle-aged (40-60 years old; n = 32); and old (>60 years old; n = 31). Erythrocyte ghosts/cell suspension from each group were incubated with ECG, EGCG, EGC and EC (10 µmol/L) for 30 min at 37°C prior to assay. Ageing significantly increased NHE activity and decreased Ca(2+) -ATPase activity. There were no significant changes in Na(+) /K(+) -ATPase activity during the ageing process. (-)-Epigallocatechin-3-gallate, EGC, ECG and EC effectively mitigated the changes in membrane transporter activity in erythrocytes from all age groups; however, the effect was more pronounced in the old age group. We hypothesize that impairment in -bound transporters may be one of the possible mechanisms underlying the pathological events during ageing. A higher intake of catechin-rich food may provide some protection against age-dependent diseases.

(-)-Epicatechin is associated with increased angiogenic and mitochondrial signalling in the hindlimb of rats selectively bred for innate low running capacity.

Alternative approaches to reduce congenital muscle dysfunction are needed in cases where the ability to exercise is limited. (-)-Epicatechin is found in cocoa and may stimulate capillarity and mitochondrial proliferation in skeletal muscle. A total of 21 male rats bred for LCR (low running capacity) from generation 28 were randomized into three groups: vehicle for 30 days (control); (-)-epicatechin for 30 days; and (-)-epicatechin for 30 days followed by 15 days without (-)-epicatechin. Groups 2 and 3 received 1.0 mg of (-)-epicatechin/kg of body mass twice daily, whereas water was given to the control group. The plantaris muscle was harvested for protein and morphometric analyses. In addition, in vitro experiments were conducted to examine the role of (-)-epicatechin on mitochondrial respiratory kinetics at different incubation periods. Treatment for 30 days with (-)-epicatechin increased capillarity (P<0.001) and was associated with increases in protein expression of VEGF (vascular endothelial growth factor)-A with a concomitant decrease in TSP-1 (thrombospondin-1) and its receptor, which remained after 15 days of (-)-epicatechin cessation. Analyses of the p38 MAPK (mitogen-activated protein kinase) signalling pathway indicated an associated increase in phosphorylation of MKK3/6 (MAPK kinase 3/6) and p38 and increased protein expression of MEF2A (myocyte enhancer factor 2A). In addition, we observed significant increases in protein expression of PGC-1α (peroxisome-proliferator-activated receptor γ co-activator 1α), PGC-1ß, Tfam and cristae abundance. Interestingly, these increases associated with (-)-epicatechin treatment remained after 15 days of cessation. Lastly, in vitro experiments indicated that acute exposure of LCR muscle to (-)-epicatechin incubation was not sufficient to increase mitochondrial respiration. The results suggest that increases in skeletal muscle capillarity and mitochondrial biogenesis are associated with 30 days of (-)-epicatechin treatment and sustained for 15 days following cessation of treatment. Clinically, the use of this natural compound may have potential application in populations that experience muscle fatigue and are unable to perform endurance exercise.

Potential role of green tea catechins in various disease therapies: progress and promise.

Green tea (from the plant Camellia sinensis), a beverage whose consumption started 5000 years ago in China, has important biological and pharmacological properties. The beneficial effects of green tea have been attributed to the presence of phenolic compounds that are powerful anti-oxidants and free iron scavengers. Of all the catechins found in green tea, namely (-)-epicatechin-3-gallate, (-)-epigallocatechin, (-)-epicatechin and (-)-epigallocatechin-3-gallate (EGCG), EGCG is the most abundant and powerful. It is widely believed that green tea may protect against death from all causes, especially cardiovascular diseases (coronary heart disease and stroke) owing to the presence of catechins associated with green tea consumption. Other health benefits include various types of cancer chemoprevention, weight loss and protective effects against neurodegenerative diseases (Alzheimer's disease and Parkinson's disease). Thus far, numerous pharmacological activities regulating disease-specific molecular targets have been reported in vitro for EGCG concentrations in the micromolar range, which are physiologically irrelevant. Although most of the studies have shown benefits with two to three cups of green tea per day, the optimal dose has not yet been established to enable any solid conclusions to be drawn regarding the various health benefits of green tea or its constituents in humans. With Phase I trials providing information on the safety profile and pharmacokinetics of EGCG, the window of opportunity is wider to undertake well-controlled long-term human studies to enable a full understanding of the protective effects of green tea catechins on various parameters in different settings.

Epigallocatechin-3-gallate reduces airway inflammation in mice through binding to proinflammatory chemokines and inhibiting inflammatory cell recruitment.

One major activity of chemokines is the recruitment of immune cells to sites of infection and inflammation. CD4(+) Th1 cells play critical roles in host defense against pathogens and in the pathogenesis of many immune-mediated diseases. It was reported that epigallocatechin-3-gallate (EGCG) exhibits anti-inflammatory properties, but the mechanisms have not been completely defined. In this study, we found that EGCG markedly decreased recruitment of murine OVA-specific Th1 cells and other inflammatory cells into the airways in a Th1 adoptive-transfer mouse model. In vitro analysis revealed that EGCG inhibited CXCR3 ligand-driven chemotaxis of murine and human cells. Surface plasmon resonance studies revealed that EGCG bound directly to chemokines CXCL9, CXCL10, and CXCL11. These results indicated that one anti-inflammatory mechanism of EGCG is binding of proinflammatory chemokines and limiting their biological activities. These findings support further development of EGCG as a potent therapeutic for inflammatory diseases.

TLR4 signaling inhibitory pathway induced by green tea polyphenol epigallocatechin-3-gallate through 67-kDa laminin receptor.

Epigallocatechin-3-gallate (EGCG), a major active polyphenol of green tea, has been shown to downregulate inflammatory responses in macrophages; however, the underlying mechanism has not been understood. Recently, we identified the 67-kDa laminin receptor (67LR) as a cell-surface EGCG receptor that mediates the anticancer action of EGCG at physiologically relevant concentrations (0.1-1 microM). In this study, we show the molecular basis for the downregulation of TLR4 signal transduction by EGCG at 1 microM in macrophages. Anti-67LR Ab treatment or RNA interference-mediated silencing of 67LR resulted in abrogation of the inhibitory action of EGCG on LPS-induced activation of downstream signaling pathways and target gene expressions. Additionally, we found that EGCG reduced the TLR4 expression through 67LR. Interestingly, EGCG induced a rapid upregulation of Toll-interacting protein (Tollip), a negative regulator of TLR signaling, and this EGCG action was prevented by 67LR silencing or anti-67LR Ab treatment. RNA interference-mediated silencing of Tollip impaired the TLR4 signaling inhibitory activity of EGCG. Taken together, these findings demonstrate that 67LR plays a critical role in mediating anti-inflammatory action of a physiologically relevant EGCG, and Tollip expression could be modulated through 67LR. These results provide a new insight into the understanding of negative regulatory mechanisms for the TLR4 signaling pathway and consequent inflammatory responses that are implicated in the development and progression of many chronic diseases.

(-)-Catechin promotes adipocyte differentiation in human bone marrow mesenchymal stem cells through PPAR gamma transactivation.

Green tea intake has been shown to confer various health benefits to patients suffering from metabolic disorders. Here, we studied the effect of several major green tea polyphenols on adipocyte differentiation in human bone marrow mesenchymal stem cells (hBM-MSCs) and compared it to the effect of representative antidiabetic drugs. (-)-Catechin was the most potent of the eight green tea polyphenols evaluated in promoting adipocyte differentiation in hBM-MSCs, and this effect was dose-dependent. (-)-Catechin increased the mRNA levels of various adipogenic markers, such as adiponectin, peroxisome proliferator-activated receptor gamma (PPARgamma), FABP4, and LPL, as measured during adipocyte differentiation in hBM-MSCs. In addition, (-)-catechin upregulated the secretion of adiponectin in hBM-MSC culture. Using a reporter gene assay and a competitive ligand binding study, (-)-catechin also significantly activated PPARgamma in a dose-dependent fashion; however, (+)-catechin, the enantiomer of (-)-catechin, was not effective as a PPARgamma agonist, which seems to imply that the effect of (-)-catechin on PPARgamma is stereospecific. In conclusion, our data suggest that (-)-catechin promotes adipocyte differentiation and increased sensitivity to insulin in part by direct activation of PPARgamma, which could be at the basis of the observed pharmacological benefits of green tea intake in reducing the risk of type 2 diabetes.

Dihydrotestosterone sensitises LNCaP cells to death induced by epigallocatechin-3-Gallate (EGCG) or an IGF-I receptor inhibitor.

BACKGROUND: Compelling evidence has accumulated for chemopreventive effects for the active component of green tea Epigallocatechin-3-Gallate (EGCG) particularly for prostate cancer (CaP). METHODS: We have assessed interactions between the effects of EGCG and two main regulators of prostate cell function, dihydrotestosterone (DHT) and insulin-like growth factor-1 (IGF-I). Using LNCaP (androgen-sensitive), PC3 and DU145 (androgen-resistant) CaP cell lines, we assessed the effect of EGCG alone on growth (0-200 microM) and on cell death (0-50 microM). RESULTS: EGCG decreased the proliferation of all the CaP cancer cells in a dose-dependent manner with an increase in apoptosis from 30 to 50 microM. With DU145 cells, a sub-apoptotic dose of EGCG (10-20 microM) reduced IGF-induced growth. With LNCaP cells, a sub-apoptotic dose of EGCG (8 microM) switched DHT from a growth promoter to a growth inhibitor. A similar reversal of DHT effect was seen in the presence of an IGF-I receptor inhibitor, AG1024 (1 microM). These responses appeared to be due to DHT sensitizing the cells to apoptosis by EGCG and AG1024 (P < 0.01 and P < 0.001 respectively). CONCLUSIONS: Our data suggests that both green tea and AG1024 are effective in inhibiting cell growth and inducing death in CaP cells but the effects of both are more effective in the presence of androgen.

Higher dietary flavone, flavonol, and catechin intakes are associated with less of an increase in BMI over time in women: a longitudinal analysis from the Netherlands Cohort Study.

BACKGROUND: Dietary flavonoids are suggested to have antiobesity effects. Prospective evidence of an association between flavonoids and body mass index (BMI) is lacking in general populations. OBJECTIVE: We assessed this association between 3 flavonoid subgroups and BMI over a 14-y period in 4280 men and women aged 55-69 y at baseline from the Netherlands Cohort Study. DESIGN: Dietary intake was estimated at baseline (1986) by a validated food-frequency questionnaire. BMI was ascertained through self-reported height (in 1986) and weight (in 1986, 1992, and 2000). Analyses were based on sex-specific quintiles for the total intake of 6 catechins and of 3 flavonols/flavones. Linear mixed effect modeling was used to assess longitudinal associations in 3 adjusted models: age only, lifestyle (age, energy intake, physical activity, smoking status, alcohol intake, type 2 diabetes, and coffee consumption), and lifestyle and diet (vegetables, fruit, fiber, grains, sugar, dessert, and dieting habits). RESULTS: After adjustment for age and confounders, the BMI (kg/m(2)) of women with the lowest intake of total flavonols/flavones and total catechins increased by 0.95 and 0.77, respectively, after 14 y. Women with the highest intake of total flavonols/flavones and total catechins experienced a significantly lower increase in BMI of 0.40 and 0.31, respectively (between group difference: P < 0.05). This difference remained after additional adjustment for dietary determinants and after stratification of median baseline BMI. In men, no significant differences in BMI change were observed over the quintiles of flavonoid intake after 14 y. CONCLUSION: Our results suggest that flavonoid intake may contribute to maintaining body weight in the general female population.

Catechins inhibit angiotensin II-induced vascular smooth muscle cell proliferation via mitogen-activated protein kinase pathway.

Catechins, components of green tea, reduce the incidence of cardiovascular diseases such as atherosclerosis. Angiotensin II (Ang II) is highly implicated in the proliferation of vascular smooth muscle cells (VSMC), resulting in atherosclerosis. The acting mechanisms of the catechins remain to be defined in the proliferation of VSMC induced by Ang II. Here we report that catechin, epicatechin (EC), epicatechingallate (ECG) or epigallocatechingallate (EGCG) significantly inhibits the Ang II-induced [3H]thymidine incorporation into the primary cultured rat aortic VSMC. Ang II increases the phosphorylation of the extracellular signal-regulated protein kinase 1/2 (ERK 1/2), c-jun-N-terminal kinase 1/2 (JNK 1/2), or p38 mitogen-activated protein kinases (MAPKs) and mRNA expression of c-jun and c-fos. The EGCG pretreatment inhibits the Ang II-induced phosphorylation of ERK 1/2, JNK 1/2, or p38 MAPK, and the expression of c-jun or c-fos mRNA. U0126, a MEK inhibitor, SP600125, a JNK inhibitor, or SB203580, a p38 inhibitor, attenuates the Ang II-induced [3H]thymidine incorporation into the VSMC. In conclusion, catechins inhibit the Ang II-stimulated VSMC proliferation via the inhibition of the Ang II-stimulated activation of MAPK and activator protein-1 signaling pathways. The antiproliferative effect of catechins may be associated with the reduced risk of cardiovascular diseases by the intake of green tea. Catechins may be useful in the development of prevention and therapeutics of vascular diseases.

Can plant biochemistry contribute to understanding of invasion ecology?

Ecologists have long searched for an explanation as to why some plant invaders become much more dominant in their naturalized range than in their native range, and, accordingly, several non-exclusive ecological hypotheses have been proposed. Recently, a biochemical explanation was proposed--the "novel weapons hypothesis"--based on findings that Centaurea diffusa and Centaurea maculosa produce bioactive compounds (weapons) that are more active against naïve plant species in the introduced range than against co-evolved species in the native range. In this Opinion article, we revise and expand this biochemical hypothesis and discuss experimental and conceptual advances and limitations.

Electron-transfer capacity of catechin derivatives and influence on the cell cycle and apoptosis in HT29 cells.

Galloylated and nongalloylated catechin conjugates with cysteine derivatives have been synthesized and evaluated for their capacity to scavenge free radicals and to influence crucial functions (cell cycle, apoptosis) in HT29 colon carcinoma cells. We show that the nonphenolic part of the molecule modified the capacity of catechins to donate hydrogen atoms and to transfer electrons to free radicals. Nongalloylated derivatives did not significantly influence either the cell cycle or apoptosis. Among the galloylated species, 4beta-[S-(O-ethyl-cysteinyl)]epicatechin 3-O-gallate, which showed a high electron-transfer capacity (5 e- per molecule), arrested the cell cycle and induced apoptosis as expected for galloylated catechins such as tea (-)-epigallocatechin 3-O-gallate. 4beta-[S-(N-Acetyl-O-methyl-cysteinyl)]epicatechin 3-O-gallate, which showed the highest hydrogen-donating capacity (10 H per molecule) while keeping the electron-transfer capacity low (2.9 e- per molecule), did not trigger any significant apoptosis. The gallate moiety did not appear to be sufficient for the pro-apoptotic effect of the catechin derivatives in HT29 cells. Instead, a high electron-transfer capacity is more likely to be behind this effect. The use of stable radicals sensitive exclusively to electron transfer may help to design molecules with either preventive scavenging action (high hydrogen donation, low electron transfer) or therapeutic pro-apoptotic activity (high electron transfer).

(-)-Epicatechin mediates beneficial effects of flavanol-rich cocoa on vascular function in humans.

Epidemiological and medical anthropological investigations suggest that flavanol-rich foods exert cardiovascular health benefits. Endothelial dysfunction, a prognostically relevant key event in atherosclerosis, is characterized by a decreased bioactivity of nitric oxide (NO) and impaired flow-mediated vasodilation (FMD). We show in healthy male adults that the ingestion of flavanol-rich cocoa was associated with acute elevations in levels of circulating NO species, an enhanced FMD response of conduit arteries, and an augmented microcirculation. In addition, the concentrations and the chemical profiles of circulating flavanol metabolites were determined, and multivariate regression analyses identified (-)-epicatechin and its metabolite, epicatechin-7-O-glucuronide, as independent predictors of the vascular effects after flavanol-rich cocoa ingestion. A mixture of flavanols/metabolites, resembling the profile and concentration of circulating flavanol compounds in plasma after cocoa ingestion, induced a relaxation in preconstricted rabbit aortic rings ex vivo, thus mimicking acetylcholine-induced relaxations. Ex vivo flavanol-induced relaxation, as well as the in vivo increases in FMD, were abolished by inhibition of NO synthase. Oral administration of chemically pure (-)-epicatechin to humans closely emulated acute vascular effects of flavanol-rich cocoa. Finally, the concept that a chronic intake of high-flavanol diets is associated with prolonged, augmented NO synthesis is supported by data that indicate a correlation between the chronic consumption of a cocoa flavanol-rich diet and the augmented urinary excretion of NO metabolites. Collectively, our data demonstrate that the human ingestion of the flavanol (-)-epicatechin is, at least in part, causally linked to the reported vascular effects observed after the consumption of flavanol-rich cocoa.