Dietary proanthocyanidins: Occurrence, dietary intake, bioavailability, and protection against cardiovascular disease

Molecular mechanisms for chemoprevention of colorectal cancer by natural dietary compounds

Colorectal cancer is one of the major causes of cancer-related mortality in both men and women worldwide. This review focuses on preventing the initiation and promotion of neoplastic growth in colorectal cancer, particularly with natural dietary compounds. Chemoprevention is defined as the use of natural dietary compounds and/or synthetic substances that can delay, prevent, or even reverse the development of adenomas, as well as the progression from adenoma to carcinoma. The molecular mechanisms of their chemopreventive action are associated with the modulation of signaling cascades, gene expressions involved in the regulation of cell proliferation, differentiation, and apoptosis and the suppression of chronic inflammation, metastasis, and angiogenesis. Here, we summarize the currently known targets and signaling pathways whereby natural dietary compounds interfere with the development of colorectal cancer, and thus providing evidence for these substances in colonic cancer chemopreventive action.

Proanthocyanidin metabolites associated with dietary fibre from in vitro colonic fermentation and proanthocyanidin metabolites in human plasma

Proanthocyanidins (PAs) or condensed tannins, a major group of dietary polyphenols, are oligomers and polymers of flavan-3-ol and flavan-3, 4-diols widely distributed in plant foods. Most literature data on PAs' metabolic fate deal with PAs that can be extracted from the food matrix by aqueous-organic solvents ( extractable proanthocyanidins). However, there are no data on colonic fermentation of non-extractable proanthocyanidins (NEPAs), which arrive almost intact to the colon, mostly associated to dietary fibre (DF). The aim of the present work was to examine colonic fermentation of NEPAs associated with DF, using a model of in vitro small intestine digestion and colonic fermentation. Two NEPA-rich materials obtained from carob pod (Ceratonia siliqua L. proanthocyanidin) and red grapes (grape antioxidant dietary fibre) were used as test samples. The colonic fermentation of these two products released hydroxyphenylacetic acid, hydroxyphenylvaleric acid and two isomers of hydroxyphenylpropionic acid, detected by HPLC-ESI-MS/MS. Differences between the two products indicate that DF may enhance the yield of metabolites. In addition, the main NEPA metabolite in human plasma was 3,4-dihydroxyphenyl acetic acid. The presence in human plasma of the same metabolites as were detected after in vitro colonic fermentation of NEPAs suggests that dietary NEPAs would undergo colonic fermentation releasing absorbable metabolites with potential healthy effects.

Plant phenolics: extraction, analysis and their antioxidant and anticancer properties

Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potent antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. In the last few years, the identification and development of phenolic compounds or extracts from different plants has become a major area of health- and medical-related research. This review provides an updated and comprehensive overview on phenolic extraction, purification, analysis and quantification as well as their antioxidant properties. Furthermore, the anticancer effects of phenolics in-vitro and in-vivo animal models are viewed, including recent human intervention studies. Finally, possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.

Anti-inflammatory activity of natural dietary flavonoids

Over the past few decades, inflammation has been recognized as a major risk factor for various human diseases. Acute inflammation is short-term, self-limiting and it's easy for host defenses to return the body to homeostasis. Chronic inflammatory responses are predispose to a pathological progression of chronic illnesses characterized by infiltration of inflammatory cells, excessive production of cytokines, dysregulation of cellular signaling and loss of barrier function. Targeting reduction of chronic inflammation is a beneficial strategy to combat several human diseases. Flavonoids are widely present in the average diet in such foods as fruits and vegetables, and have been demonstrated to exhibit a broad spectrum of biological activities for human health including an anti-inflammatory property. Numerous studies have proposed that flavonoids act through a variety mechanisms to prevent and attenuate inflammatory responses and serve as possible cardioprotective, neuroprotective and chemopreventive agents. In this review, we summarize current knowledge and underlying mechanisms on anti-inflammatory activities of flavonoids and their implicated effects in the development of various chronic inflammatory diseases.

Should Red Wine Be Considered a Functional Food?

  Functional foods may be regarded as foods that have nutritional value, but in particular, they also have beneficial effects on one or more body functions. Thus, functional foods may improve health and/or reduce the risk of developing certain diseases when taken in amounts that can be consumed in a normal diet. Based on nearly 2 decades of research since the term "French paradox" was first coined in 1992, wine would appear to fit this definition. Yet there seems to be reluctance to consider wine as a functional food. In this review, we present an overview of the accumulated evidence for the health benefits of wine-and its key phenolic components such as resveratrol, quercetin, catechin-and show that these alone are not enough to firmly establish wine as a functional food. What is required is to create clearly defined products based on wine that are targeted to consumers' needs and expectations when it comes to purchasing functional foods. Moreover, the crucial question of alcohol and health also needs to be addressed by the functional food industry. Suggestions are presented for working through this issue, but in many regards, wine is like any other food-it should be consumed sensibly and in amounts that are beneficial to health. Overindulgence of any kind does not promote good health.

Complex flavonoids in cocoa: synthesis and degradation by intestinal microbiota

Rarely occurring flavan-3-ol derivatives such as C-glycosides can be generated during food processing, for example, by cocoa production. These astringent taste compounds may also exert interesting behavior toward microbial metabolism, as other C-glycosides have been shown to be quite stable. Oligomeric flavan-3-ols, the procyanidins, bear also a C-C bond between the main moieties and are suspected to resist microbial metabolism for a prolonged time compared to other flavonoids. This paper describes a semisynthetic approach for the generation of flavan-3-ol C-glycosides. Results of incubation experiments studying five flavan-3-ol C-glycosides bearing different sugars, linkage positions, and stereochemistries are presented as well as the behavior of di- and trimeric B-type procyanidins toward intestinal microbiota. Low molecular weight degradation products are considered as well as concentration-time courses of degraded and liberated compounds. All metabolic studies were performed with the well-proven pig cecum model.

Dietary flavonoid quercetin stimulates vasorelaxation in aortic vessels

Considerable epidemiological evidence indicates that dietary consumption of moderate levels of polyphenols decreases both the incidence of cardiovascular disease and the mortality associated with myocardial infarction. Molecular mechanisms of this cardiovascular protection remain uncertain but can involve changes in rates of nitric oxide (NO) generation by endothelial nitric oxide synthase (eNOS). We examined the vascular responses to quercetin using a combination of biochemical and vessel function criteria. Quercetin treatment for 30min enhanced relaxation of rat aortic ring segments. Moreover, the addition of L-NAME (100muM) or charybdotoxin (ChTx) blocked quercetin-mediated vasorelaxation thus demonstrating the effect was partially dependent on NOS and endothelium-derived hyperpolarizing factor (EDHF). Additionally, bovine aortic endothelial cells (BAEC) treated with quercetin showed a rapid increase of intracellular Ca(2+) concentrations as well as a dose- and time-dependent stimulation of eNOS phosphorylation with a concomitant increase in NO production. These results demonstrate that quercetin-mediated stimulation of eNOS phosphorylation increases NO bioavailability in endothelial cells and can thus play a role in the vascular protective effects associated with improved endothelial cell function.

Modulatory effect of grape-seed procyanidins on local and systemic inflammation in diet-induced obesity rats

Chronic low-grade inflammation in obesity is characterized by macrophage accumulation in white adipose tissue (WAT) and abnormal cytokine production. We tested the hypothesis that grape-seed procyanidin extract (PE), with known anti-inflammatory and antioxidant effects, would improve local and systemic inflammation in diet-induced obesity rats. First, we analyzed the preventive effects of procyanidins (30 mg/kg per day) on rats fed a 60% kcal fat diet for 19 weeks. Second, we induced cafeteria diet obesity for 13 weeks to investigate the corrective effects of two PE doses (25 and 50 mg/kg per day) for 10 and 30 days. In the preventive model, PE group had reduced not only body weight but also plasmatic systemic markers of inflammation tumor necrosis factor-α (TNF-α) and C-reactive protein (CRP). The PE preventive treatment significantly showed an increased adiponectin expression and decreased TNF-α, interleukin-6 and CRP expression in mesenteric WAT and muscle TNF-α. A reduced NF-κB activity in liver is also observed which can be related to low expression rates of hepatic inflammatory markers found in PE group. Finally, PE dietary supplementation is linked to a reduced expression of Emr1 (specific marker of macrophage F4/80), which suggests a reduced macrophage infiltration of WAT. In the corrective model, however, only the high dose of PE reduced CRP plasma levels in the short treatment without changes in plasmatic TNF-α. In conclusion, orally ingested PE helps preventing imbalanced obesity cytokine pattern, but its corrective effects need to be further investigated. The dietary regular intake of food or drinks containing procyanidins might help prevent low-grade inflammatory-related diseases.

Polyphenolic apple extracts: effects of raw material and production method on antioxidant effectiveness and reduction of DNA damage in Caco-2 cells

A diet rich in fruits and vegetables is commonly perceived to be associated with reduced cancer risk, attributed to its high content of polyphenols. As apples represent a major polyphenol source in Western countries, we studied differentially produced extracts (1-100 microg/mL): two from different apple juices (AEs), one from pomace (APE), and one peel extract (PE) on their potential to reduce DNA oxidation damage and induce antioxidant defense in Caco-2 cells. Additionally, we measured direct antioxidant capacity (TEAC/ORAC) of the extracts. Quercetin-rich PE and APE most effectively diminished DNA damage and ROS level after 24 h incubation (PE > APE), whereas the AEs were only moderately effective. GPx activity was diminished for all extracts, with AEs > APE > PE. Direct antioxidant activity decreased in the order AEs > PE > APE, displaying no significant correlation with cellular markers. In conclusion, apple phenolics at low, nutritionally relevant concentrations may protect intestinal cells from ROS-induced DNA damage, mediated by cellular defense mechanisms rather than by antioxidant activity.

Healthy properties of proanthocyanidins

Proanthocyanidins, also named condensed tannins, are the result of flavanols condensation. Oligomers and polymers of proanthocyanidins can widely be found in the plant kingdom, as in fruits and berries, seeds, flowers, and leaves. They have a putative role as antioxidants, and they affect the inflammatory process via calcium-dependent release of nitric oxide and protect against H(2)O(2)-induced lipid peroxidation. They also demonstrated a role in cardiovascular diseases via vessel relaxation and LDL oxidation inhibition. These condensed tannins have also shown activities that improve diabetic complications, such as neuropathy, retinopathy, or nephropathy, including a decrease in serum glucose and advanced glycation end products. Furthermore, proanthocyanidins have evidenced anticancer properties by mitigating tumor development through induction of apoptosis or inhibition of cell proliferation. Finally, they are able to produce antiadhesive actions against bacteria in urinary and dental infections, including Escherichia coli and Streptococcus mutans. Hence, proanthocyanidins are considered as beneficial molecules in preventing or treating many diseases and pathological conditions. Therefore, finding out more about condensed tannins bioavailability, and understanding the regulatory genes and pathways involved in their effects should be aimed in future research.

Apple proanthocyanidins do not reduce the induction of preneoplastic lesions in the colon of rats associated with human microbiota

Since the gut microbiota metabolizes various dietary constituents unabsorbed by the small intestine and modulates colon function, it plays an essential role in colon carcinogenesis. First, we have developed a model of human microbiota-associated rats (HMA), fed a human-type diet and injected with 1-2,dimethylhydrazine (DMH). We observed that the number and size of DMH-induced aberrant crypt foci (ACF) were significantly higher in HMA rats than in germ-free or conventional rats. Second, we used this model to assess the protective effect of an apple proanthocyanidin-rich extract (APE) on colon carcinogenesis. In this model, ACF number and multiplicity were not reduced by APE at 0.001% and 0.01% in drinking water. They were higher with APE 0.1% than with APE 0.01%. Therefore, the cross-talk between human microbiota and the colon epithelium should be taken into account in carcinogenesis models. Moreover, attention should be paid prior to using proanthocyanidin extracts as dietary supplements for humans.

Hypolipidemic effects of proanthocyanidins and their underlying biochemical and molecular mechanisms

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies strongly suggest that proanthocyanidins protect against cardiovascular diseases. Despite the antioxidant and anti-inflammatory properties of these flavonoids, one of the mechanisms by which proanthocyanidins exert their cardiovascular protection is improving lipid homeostasis. Animal studies demonstrate that proanthocyanidins reduce the plasma levels of atherogenic apolipoprotein B-triglyceride-rich lipoproteins and LDL-cholesterol but increase antiatherogenic HDL-cholesterol. The results in humans, however, are less clear. This review summarizes the results that have been published on plasma triglyceride, apolipoprotein B, HDL-cholesterol and LDL-cholesterol levels in humans and animal models in response to proanthocyanidin extracts and proanthocyanidin-rich foods. The physiological processes and biochemical pathways that are related to lipid homeostasis and affected by proanthocyanidin consumption are also discussed. Intestinal lipid absorption, chylomicron secretion by the intestine and VLDL secretion by the liver are the processes that are most repressed by proanthocyanidins, which, therefore, induce hypolipidemic effects.

An R2R3 MYB transcription factor associated with regulation of the anthocyanin biosynthetic pathway in Rosaceae

BACKGROUND

The control of plant anthocyanin accumulation is via transcriptional regulation of the genes encoding the biosynthetic enzymes. A key activator appears to be an R2R3 MYB transcription factor. In apple fruit, skin anthocyanin levels are controlled by a gene called MYBA or MYB1, while the gene determining fruit flesh and foliage anthocyanin has been termed MYB10. In order to further understand tissue-specific anthocyanin regulation we have isolated orthologous MYB genes from all the commercially important rosaceous species.

RESULTS

We use gene specific primers to show that the three MYB activators of apple anthocyanin (MYB10/MYB1/MYBA) are likely alleles of each other. MYB transcription factors, with high sequence identity to the apple gene were isolated from across the rosaceous family (e.g. apples, pears, plums, cherries, peaches, raspberries, rose, strawberry). Key identifying amino acid residues were found in both the DNA-binding and C-terminal domains of these MYBs. The expression of these MYB10 genes correlates with fruit and flower anthocyanin levels. Their function was tested in tobacco and strawberry. In tobacco, these MYBs were shown to induce the anthocyanin pathway when co-expressed with bHLHs, while over-expression of strawberry and apple genes in the crop of origin elevates anthocyanins.

CONCLUSIONS

This family-wide study of rosaceous R2R3 MYBs provides insight into the evolution of this plant trait. It has implications for the development of new coloured fruit and flowers, as well as aiding the understanding of temporal-spatial colour change.

Crystal structure and catalytic mechanism of leucoanthocyanidin reductase from Vitis vinifera

Leucoanthocyanidin reductase (LAR) catalyzes the NADPH-dependent reduction of 2R,3S,4S-flavan-3,4-diols into 2R,3S-flavan-3-ols, a subfamily of flavonoids that is important for plant survival and for human nutrition. LAR1 from Vitis vinifera has been co-crystallized with or without NADPH and one of its natural products, (+)-catechin. Crystals diffract to a resolution between 1.75 and 2.72 A. The coenzyme and substrate binding pocket is preformed in the apoprotein and not markedly altered upon NADPH binding. The structure of the abortive ternary complex, determined at a resolution of 2.28 A, indicates the ordering of a short 3(10) helix associated with substrate binding and suggests that His122 and Lys140 act as acid-base catalysts. Based on our 3D structures, a two-step catalytic mechanism is proposed, in which a concerted dehydration precedes an NADPH-mediated hydride transfer at C4. The dehydration step involves a Lys-catalyzed deprotonation of the phenolic OH7 through a bridging water molecule and a His-catalyzed protonation of the benzylic hydroxyl at C4. The resulting quinone methide serves as an electrophilic target for hydride transfer at C4. LAR belongs to the short-chain dehydrogenase/reductase superfamily and to the PIP (pinoresinol-lariciresinol reductase, isoflavone reductase, and phenylcoumaran benzylic ether reductase) family. Our data support the concept that all PIP enzymes reduce a quinone methide intermediate and that the major role of the only residue that has been conserved from the short-chain dehydrogenase/reductase catalytic triad (Ser...TyrXXXLys), that is, lysine, is to promote the formation of this intermediate by catalyzing the deprotonation of a phenolic hydroxyl. For some PIP enzymes, this lysine-catalyzed proton abstraction may be sufficient to trigger the extrusion of the leaving group, whereas in LAR, the extrusion of a hydroxide group requires a more sophisticated mechanism of concerted acid-base catalysis that involves histidine and takes advantage of the OH4, OH5, and OH7 substituents of leucoanthocyanidins.

Polyphenolic compounds in seeds from some grape cultivars grown in Serbia

Seed extracts from eight grape cultivars (Vitis vinifera) growing in Serbia were screened for their polyphenolic composition by means of HPLC/PDA/ESI/MS analysis. The study revealed 34 phenolic compounds belonging to the following groups: flavan-3-ol monomers, proanthocyanidins, flavonols, hydroxycinnamic acids and hydroxybenzoic acid derivatives. The quantities of the main constituents were determined using PDA/HPLC. Qualitative and quantitative differences among the cultivars were observed.

Chemistry of secondary polyphenols produced during processing of tea and selected foods

This review will discuss recent progress in the chemistry of secondary polyphenols produced during food processing. The production mechanism of the secondary polyphenols in black tea, whisky, cinnamon, and persimmon fruits will be introduced. In the process of black tea production, tea leaf catechins are enzymatically oxidized to yield a complex mixture of oxidation products, including theaflavins and thearubigins. Despite the importance of the beverage, most of the chemical constituents have not yet been confirmed due to the complexity of the mixture. However, the reaction mechanisms at the initial stages of catechin oxidation are explained by simple quinone-phenol coupling reactions. In vitro model experiments indicated the presence of interesting regio- and stereoselective reactions. Recent results on the reaction mechanisms will be introduced. During the aging of whisky in oak wood barrels, ellagitannins originating from oak wood are oxidized and react with ethanol to give characteristic secondary ellagitannins. The major part of the cinnamon procyanidins is polymerized by copolymerization with cinnamaldehyde. In addition, anthocyanidin structural units are generated in the polymer molecules by oxidation which accounts for the reddish coloration of the cinnamon extract. This reaction is related to the insolubilization of proanthocyanidins in persimmon fruits by condensation with acetaldehyde. In addition to oxidation, the reaction of polyphenols with aldehydes may be important in food processing.

Tannins: current knowledge of food sources, intake, bioavailability and biological effects

Tannins are a unique group of phenolic metabolites with molecular weights between 500 and 30 000 Da, which are widely distributed in almost all plant foods and beverages. Proanthocyanidins and hydrolysable tannins are the two major groups of these bioactive compounds, but complex tannins containing structural elements of both groups and specific tannins in marine brown algae have also been described. Most literature data on food tannins refer only to oligomeric compounds that are extracted with aqueous-organic solvents, but a significant number of non-extractable tannins are usually not mentioned in the literature. The biological effects of tannins usually depend on their grade of polymerisation and solubility. Highly polymerised tannins exhibit low bioaccessibility in the small intestine and low fermentability by colonic microflora. This review summarises a new approach to analysis of extractable and non-extractable tannins, major food sources, and effects of storage and processing on tannin content and bioavailability. Biological properties such as antioxidant, antimicrobial and antiviral effects are also described. In addition, the role of tannins in diabetes mellitus has been discussed.

Proanthocyanidins and the risk of colorectal cancer in Italy

Proanthocyanidins are a group of polymers of flavanols. Animal and in vitro studies suggest they decrease cancer risk, particularly of colorectal cancer. We used data from an Italian case-control study to investigate whether proanthocyanidins are related to colorectal cancer risk. Cases were 1,953 patients with incident, histologically confirmed colorectal cancer (1,225 colon cancers, 728 rectal cancers). Controls were 4,154 patients admitted for acute, non-neoplastic conditions. A reproducible and valid food frequency questionnaire was used. We estimated odds ratios (ORs) through multiple logistic regression models, including terms for potential confounding factors, and energy intake. A trend of decreasing risk with increasing intake of proanthocyanidins emerged for all classes except monomers. The OR for the highest vs. the lowest quintile of intake was 0.82 for monomers and dimers combined, 0.88 for monomers, 0.75 for dimers, 0.74 for all polymers with three or more mers, 0.84 for trimers, 0.80 for 4-6 mers, 0.79 for 7-10 mers, 0.69 for more than 10 mers, and 0.74 for total proanthocyanidins. The associations were apparently stronger for rectal than for colon cancer, in the absence of significant heterogeneity. These results may explain the protective effect of vegetables and fruit on colorectal cancer.

Advanced separation methods of food anthocyanins, isoflavones and flavanols

In recent years, increasing knowledge of the positive health effects of food polyphenols has prompted the need to develop new separation techniques for their extraction, fractionation and analysis. This article provides an updated and exhaustive review of the application of counter-current chromatography, high performance liquid chromatography, capillary electrophoresis, and their hyphenation with mass spectrometry to the study of food polyphenols. Flavonoids constitute the largest class of polyphenols, widely spread in the plant kingdom and common in human diet which has been the most widely studied with respect to their antioxidant and biological activities. The main subgroups are anthocyanins, catechins, isoflavones, flavonols and flavones. They are reported to exhibit antioxidant, anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-thrombotic, and immune modulating functions, among others. Since red fruit anthocyanins, soy isoflavones and flavanols from grapes and teas are currently the most used phenolic compounds for producing new nutraceuticals and functional foods, this review is focused on these three flavonoid groups.

Developmental, genetic and environmental factors affect the expression of flavonoid genes, enzymes and metabolites in strawberry fruits

The influence of internal (genetic and developmental) and external (environmental) factors on levels of flavonoid gene transcripts, enzyme activity and metabolites was studied in fruit of six cultivated strawberry (Fragaria x ananassa Duch.) genotypes grown at two Italian locations. Gene expression and enzyme activity showed development- and genotype-associated patterns, revealing gene coordination. Analysis clarified the regulation mechanism of the hydroxylation status of the B-ring of the major flavonoid pools and pointed out examples of genotype-specific post-transcriptional regulation mechanisms and key steps of pathway regulation in strawberry fruits. Metabolite profiles were strongly affected by development and genotype. Flavan-3-ols, their proanthocyanidin (PA) derivatives and anthocyanins were the most abundant metabolites. Flavonol levels and PA-associated traits (epicatechin/catechin ratio and mean degree of polymerization) showed significant environmental effects. Multivariate and correlation analyses determined the relationships among genes, enzymes and metabolites. The combined molecular and biochemical information elucidated more in depth the role of genetic and environmental factors on flavonoid metabolism during strawberry fruit development, highlighting the major impact of developmental processes, and revealing genotype-dependent differences and environmental effects on PA-related traits.

Role of dietary polyphenols in platelet aggregation. A review of the supplementation studies

Epidemiological studies suggest that high polyphenols intake from diet is associated with reduced risk for cardiovascular diseases. Platelet aggregation is a crucial mechanism in the pathogenesis and clinical expression of coronary acute syndrome, and there is extensive evidence that antiplatelet therapy reduces cardiovascular disease risk. In this review, the available literature on the effect of polyphenols supplementation on platelet aggregation in humans or animal models has been critically analyzed, taking into consideration the different experimental protocols employed. In some studies, polyphenols supplementation did not show any effect on platelet aggregation. However, in the most of the studies, polyphenols supplementation, either as purified compounds or food extracts, showed some inhibitory effects, both in humans and in animal models. The extent of the inhibition varies in a wide range, depending on the experimental conditions used. The observed inhibitory effect of polyphenols on platelet aggregation might explain, at least in part, the epidemiological data on beneficial effect of dietary polyphenols on cardiovascular disease risk and suggests a role for polyphenols in helping to prevent cardiovascular diseases.

Dietary procyanidins enhance transcriptional activity of bile acid-activated FXR in vitro and reduce triglyceridemia in vivo in a FXR-dependent manner

Consumption of dietary flavonoids has been associated with reduced mortality and risk of cardiovascular disease, partially by reducing triglyceridemia. We have previously reported that a grape seed procyanidin extract (GSPE) reduces postprandial triglyceridemia in normolipidemic animals signaling through the orphan nuclear receptor small heterodimer partner (SHP) a target of the bile acid receptor farnesoid X receptor (FXR). Our aim was to elucidate whether FXR mediates the hypotriglyceridemic effect of procyanidins. In FXR-driven luciferase expression assays GSPE dose-dependently enhanced FXR activity in the presence of chenodeoxycholic acid. GSPE gavage reduced triglyceridemia in wild type mice but not in FXR-null mice, revealing FXR as an essential mediator of the hypotriglyceridemic actions of procyanidins in vivo. In the liver, GSPE downregulated, in an FXR-dependent manner, the expression of the transcription factor steroid response element binding protein 1 (SREBP1) and several SREBP1 target genes involved in lipogenesis, and upregulated ApoA5 expression. Altogether, our results indicate that procyanidins lower triglyceridemia following the same pathway as bile acids: activation of FXR, transient upregulation of SHP expression and subsequent downregulation of SREBP1 expression. This study adds dietary procyanidins to the arsenal of FXR ligands with potential therapeutic use to combat hypertriglyceridemia, type 2 diabetes and metabolic syndrome.

Metabolite profiling of fecal water extracts from human colorectal cancer

Colorectal cancer is the second leading cause of cancer death in developed countries. There is a need for better preventive strategies to improve the outcome of this disease. The increasing availability of high-throughput methodologies opens up new possibilities for screening new markers. The application of NMR metabolic profiling to fecal water extracts has interesting potential as a diagnostic tool for detecting colorectal cancer. We obtained NMR metabolic profiles of fecal water extracts from patients with colorectal cancer and healthy individuals, to characterize possible differences between them and to identify potential diagnostic markers. Our results show that metabolic profiling of fecal water extracts is a cheap, reproducible and effective method for detecting colorectal cancer markers and therefore complements other stool-screening methods. A low concentration of short-chain fatty acids, such as acetate and butyrate, previously associated with the development of colorectal cancer, appears to be the most effective marker. Concentrations of proline and cysteine, which are major components of most colonic epithelium mucus glycoproteins, also display significant changes in samples from colorectal cancer. Differentiation between fecal water extracts from controls and patients with colorectal cancer by NMR spectroscopy combined with chemometric techniques opens up new possibilities for developing new, efficient, high-throughput screening protocols.

Hop proanthocyanidins induce apoptosis, protein carbonylation, and cytoskeleton disorganization in human colorectal adenocarcinoma cells via reactive oxygen species

Proanthocyanidins (PCs) have been shown to suppress the growth of diverse human cancer cells and are considered as promising additions to the arsenal of chemopreventive phytochemicals. An oligomeric mixture of PCs from hops (Humulus lupulus) significantly decreased cell viability of human colon cancer HT-29 cells in a dose-dependent manner. Hop PCs, at 50 or 100 microg/ml, exhibited apoptosis-inducing properties as shown by the increase in caspase-3 activity. Increased levels of intracellular reactive oxygen species (ROS) was accompanied by an augmented accumulation of protein carbonyls. Mass spectrometry-based proteomic analysis in combination with 2-alkenal-specific immunochemical detection identified beta-actin and protein disulfide isomerase as major putative targets of acrolein adduction. Incubation of HT-29 cells with hop PCs resulted in morphological changes that indicated disruption of the actin cytoskeleton. PC-mediated hydrogen peroxide (H2O2) formation in the cell culture media was also quantified; but, the measured H2O2 levels would not explain the observed changes in the oxidative modifications of actin. These findings suggest new modes of action for proanthocyandins as anticarcinogenic agents in human colon cancer cells, namely, promotion of protein oxidative modifications and cytoskeleton derangement.

Inhibitory effects of grape seed procyanidins on foam cell formation in vitro

Human and animal studies have demonstrated that procyanidin-rich diets reduce the risk of cardiovascular diseases and atherosclerosis. Some beneficial effects have been attributed to the well-known antioxidant activity of procyanidins. This study investigated another potential corrective role of procyanidins in cholesterol flux and inflammation in macrophage-derived foam cells. RAW 264.7 macrophages were cultured with moderately oxidized LDL (oxLDL), minimally oxidized LDL (moxLDL), or LPS (0.5 microg/mL) and oxLDL (LPS + oxLDL) to induce foam cells. Then, cells were treated with procyanidins derived from grape seed (PE, 45 microg/mL) for the last 12 h of incubation with the different lipoproteins (25 microg/mL). After lipid extraction, it was determined that total and esterified cholesterol and triglyceride accumulations in foam cells were increased by lipoprotein treatment but reduced by PE incubation. To asses the effect of PE on gene expression, the relative mRNA levels of CD36, ABCA1, iNOS, COX-2, and IkappaBalpha were determined by RT-PCR. It was shown that PE reduced the oxLDL scavenger receptor expression (CD36) and enhanced ATP-binding cassette A1 (ABCA1) expression, a key regulator of macrophage cholesterol efflux. PE also down-regulated inflammatory-related genes such as inducible nitric oxide synthase (iNOS) and kappa beta inhibitor-alpha (IkappaBalpha) without modifying COX-2 expression. In conclusion, evidence is provided that procyanidins may attenuate the development of foam cell formation by reducing cholesterol accumulation and modulating the expression of key genes in cholesterol flux and inflammation.

Protective Effects of Proanthocyanidin on Cerulein-induced Acute Pancreatic Inflammation in Rats

Background

The aim of this study was to assess the possible protective effect of proanthocyanidin against cerulein-induced acute pancreatic inflammation (AP) and oxidative injury.

Methods

Sprague-Dawley rats were pretreated with proanthocyanidine (100 mg/kg, orally) or saline 15 min before cerulein was given by 20 µg/kg subcutaneously at 1-h intervals within 4 hours. Six hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1b). Pancreas tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na⁺, K⁺-ATPase and myeloperoxidase (MPO) activities. Formation of reactive oxygen species in pancreatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes, while the extent of tissue injury was analyzed microscopically.

Results

Acute pancreatitis caused a significant decrease in tissue GSH level and Na⁺, K⁺-ATPase activity, which was accompanied with significant increases in the pancreatic MDA, luminol and lucigenin chemiluminescences (CL) levels and MPO activity. Similarly TNF-α and IL-1β levels were elevated in the pancreatic group as compared to control group. On the other hand, proanthocyanidin treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by cerulein.

Conclusions

Proanthocyanidine can ameliorate pancreatic injury induced by cerulein in rats, this result suggests that proanthocyanidin may have utility in treating acute pancreatititis.

Dietary procyanidins lower triglyceride levels signaling through the nuclear receptor small heterodimer partner

Hypertriglyceridemia is an independent risk factor in the development of cardiovascular diseases, and we have previously reported that oral administration of a grape seed procyanidin extract (GSPE) drastically decreases plasma levels of triglycerides (TG) and apolipoprotein B (ApoB) in normolipidemic rats, with a concomitant induction in the hepatic expression of the nuclear receptor small heterodimer partner (NR0B2/SHP). Our objective in this study was to elucidate whether SHP is the mediator of the reduction of TG-rich ApoB-containing lipoproteins triggered by GSPE. We show that GSPE inhibited TG and ApoB secretion in human hepatocarcinoma HepG2 cells and had and hypotriglyceridemic effect in wild-type mouse. The TG-lowering action of GSPE was abolished in HepG2 cells transfected with a SHP-specific siRNA and in a SHP-null mouse. Moreover, in mouse liver, GSPE downregulated several lipogenic genes, including steroid response element binding protein 1c (SREBP-1c), and upregulated carnitine palmitoyltransferase-1A (CPT-1A) and apolipoprotein A5 (ApoA5), in a SHP-dependent manner. In HepG2 cells GSPE also inhibited ApoB secretion, but in a SHP-independent manner. In conclusion, SHP is a key mediator of the hypotriglyceridemic response triggered by GSPE. This novel signaling pathway of procyanidins through SHP may be relevant to explain the health effects ascribed to the regular consumption of dietary flavonoids.

Biosynthesis and genetic regulation of proanthocyanidins in plants

Proanthocyanidins (PAs), also known as condensed tannins, are a group of polyphenolic secondary metabolites synthesized in plants as oligomers or polymers of flavan-3-ol units via the flavonoid pathway. Due to their structural complexity and varied composition, only in the recent years has the study on the biosynthesis and regulation of PAs in plants taken off, although some details of the synthetic mechanism remain unclear. This paper aims to summarize the status of research on the structures of PAs in plants, the genes encoding key enzymes of biosynthetic pathway, the transport factors, the transcriptional regulation of PA biosynthesis and the genetic manipulation of PAs. The problems of this field were also discussed, including the nature of the final "enzyme" which catalyzes the polymerization reaction of PAs and the possible mechanism of how the elementary units of flavanols are assembled in vivo.

Functional components in peanuts

Peanut is one of the most widely used legumes due to its nutrition and taste. The fact that is has been recognized recently as a functional food, its evaluation for its role in a heart-healthy diet has received tremendous attention. Functional compounds have been isolated, identified, quantified, and even enhanced to maximize the amount for adequate health benefits. The peanut industry's byproducts such as peanut hulls and shells, skins, and even leaves and roots have also been identified as possible sources of bioactive compounds. New uses for these underutilized renewable sources can create new market opportunities and increase the value of agricultural residues.

Fractionation of polyphenol-enriched apple juice extracts to identify constituents with cancer chemopreventive potential

Apples and apple juices are widely consumed and rich sources of phytochemicals. The aim of the present study was to determine which apple constituents contribute to potential chemopreventive activities, using a bioactivity-directed approach. A polyphenol-enriched apple juice extract was fractionated by various techniques. Extract and fractions were tested in a series of test systems indicative of cancer preventive potential. These test systems measured antioxidant effects, modulation of carcinogen metabolism, anti-inflammatory and antihormonal activities, and antiproliferative potential. Regression analyses indicated that 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging potential correlated with the sum of low molecular weight (LMW) antioxidants (including chlorogenic acid, flavan-3-ols, and flavonols) and procyanidins, whereas peroxyl radicals were more effectively scavenged by LMW compounds than by procyanidins. Quercetin aglycone was identified as a potent Cyp1A inhibitor, whereas phloretin and (-)-epicatechin were the most potent cyclooxygenase 1 (Cox-1) inhibitors. Aromatase and Cyp1A inhibitory potential and cytotoxicity toward HCT116 colon cancer cells increased with increasing content in procyanidins. Overall, apple juice constituents belonging to different structural classes have distinct profiles of biological activity in these in vitro test systems. Since carcinogenesis is a complex process, combination of compounds with complementary activities may lead to enhanced preventive effects.

Grapes and human health: a perspective

Grapes are a valuable source of numerous phytonutrients, including the intensively studied constituent, resveratrol. A question worth addressing is the potential of dietary grape consumption to positively modulate human health. Many studies have suggested cardiovascular benefits, and some work has indicated cancer chemopreventive activity. Data are particularly compelling in the area of skin cancer prevention. With financial support provided by the California Table Grape Commission, novel and exciting preliminary data are emerging from independent research suggesting beneficial activity against other less prevalent but devastating illnesses, such as Alzheimer's disease and urinary bladder dysfunction. It is further suggested that some of the copious amounts of data obtained with resveratrol may be relevant to grape consumption, especially responses that can be mediated by low concentrations of the substance. Whether future specific health claims will be sought from or allowed by regulatory authorities is not known, but based on existing data, it is clear that grapes should be considered an integral component of fruit and vegetable enriched diets that are recommended by health authorities and widely accepted as beneficial for human health and disease prevention.

New approach for the synthesis and isolation of dimeric procyanidins

A semisynthetic approach for the strategic formation of various procyanidins has been developed. Procyanidin-rich grape seed extracts were reacted with flavan-3-ols under acid catalysis. The reaction enables the formation of dimeric procyanidins and the elimination of higher oligomeric and polymeric procyanidins through degradation. An easy and fast method for the isolation of large amounts of procyanidins after semisynthetic formation by high-speed countercurrent chromatography is presented. Dimeric procyanidins (B1, B2, B3, B4, B5, and B7) were obtained and isolated. Furthermore, galloylated dimeric procyanidins [(-)-epicatechin-3- O-gallate-4beta-->8-(+)-catechin, (-)-epicatechin-3- O-gallate-4beta-->8-(-)-epicatechin, (-)-epicatechin-3- O-gallate-4beta-->6-(-)-epicatechin, and (-)-epicatechin-4beta-->8-(-)-epicatechin-3- O-gallate], as well as trimeric procyanidins [C1, (-)-epicatechin-4beta-->6-(-)-epicatechin-4beta-->8-(-)-epicatechin, and (-)-epicatechin-4beta-->6-(-)-epicatechin-4beta-->6-(+)-catechin] were obtained and isolated as side products. This approach also afforded gambiriins A1 and A2, which were all isolated and unambiguously identified, and the novel 3-(2,4,6-trihydroxyphenyl)-1-(3,4-dihydroxyphenyl)-propan-2-ol-1beta-->8-(-)-epicatechin (gambiriin A4).

Grape-seed procyanidins prevent low-grade inflammation by modulating cytokine expression in rats fed a high-fat diet

OBJECTIVE

The main objective of this study was to evaluate the effect of procyanidin intake on the level of inflammatory mediators in rats fed a hyperlipidic diet, which are a model of low-grade inflammation as they show an altered cytokine production.

DESIGN

Male Zucker Fa/fa rats were randomly grouped to receive a low-fat (LF) diet, a high-fat (HF) diet or a high-fat diet supplemented with procyanidins from grape seed (HFPE) (3.45 mg/kg feed) for 19 weeks and were then euthanized. We determined biochemical parameters, C-reactive protein (CRP) and IL-6 levels in plasma. Adipose tissue depots and body weight were also determined. We assessed CRP, IL-6, TNF-alpha and adiponectin gene expression in liver and white adipose tissue (WAT).

RESULTS

As expected, rats fed the HF diet show an enhanced production of CRP. Our results demonstrate that the HFPE diet decreases rat plasma CRP levels but not IL-6 levels. The decrease in plasma CRP in HFPE rats is related to a down-regulation of CRP mRNA expression in the liver and mesenteric WAT. We have also shown a decrease in the expression of the proinflammatory cytokines TNF-alpha and IL-6 in the mesenteric WAT. In contrast, adiponectin mRNA is increased in this tissue due to the procyanidin treatment. As previously reported, CRP plasma levels correlate positively with its expression in the mesenteric WAT, suggesting that procyanidin extract (PE) modulates CRP at the synthesis level. CRP plasma levels also correlate positively with body weight. As expected, body weight is associated with the adiposity index. Also, TNF-alpha expression and IL-6 expression have a strong positive correlation. In contrast, the expression of the anti-inflammatory cytokine adiponectin correlates negatively with the expression of TNF-alpha and IL-6 in the mesenteric WAT.

CONCLUSION

These results suggest a beneficial effect of PE on low-grade inflammatory diseases, which may be associated with the inhibition of the proinflammatory molecules CRP, IL-6 and TNF-alpha and the enhanced production of the anti-inflammatory cytokine adiponectin. These findings provide a strong impetus to explore the effects of dietary polyphenols in reducing obesity-related adipokine dysregulation to manage cardiovascular and metabolic risk factors.

Diet and healthy ageing 2100: will we globalise local knowledge systems?

Diet and health clearly are linked intrinsically. Today, more than ever food is functionalized and tailor made for specific groups (e.g. athletes, the elderly, and people with specific conditions). Increased life expectancy has resulted in an increase in the quest for diets which allow for a healthy ageing. In looking back 100 years, we try to assess how of our diets will evolve in the next 100 years and how this may be linked to a 'healthier ageing'. Our argument centres around a series of dichotomies which we used to explain the main changes in dietary habits and how this impacts on health--the continuous move from dietary traditions which are local, low in technological input and based on empiricism, to diets which are global, require high technological input and are science-based. The innovations our societies have achieved over the last century have allowed us to improve our diet based on a better scientific understanding of the health benefits of such diets, but this is often not achieved due to commercial considerations. This will require that all sectors of the food industry work towards healthy and economically affordable diets. In addition, there will be a continuous demand by the consumers to ascertain that 'our' foods are not only healthy but also convenient and easy to prepare. Healthy ageing will require us to look at a multitude of aspects of foods, to integrate this knowledge and to apply it in all sectors of food production.

(1)H NMR metabolite profiling of feces as a tool to assess the impact of nutrition on the human microbiome

Current research increasingly recognizes the human gut microbiome as a metabolically versatile biological 'digester' that plays an essential role in regulating the host metabolome. Gut microbiota recover energy and biologically active molecules from food that would otherwise be washed out of the intestinal tract without benefit. In this study, a protocol for NMR-based metabolite profiling has been developed to access the activity of the microbiome. The physicochemical properties of fecal metabolites have been found to strongly affect the reproducibility and coverage of the profiles obtained. Metabolite profiles generated by water and methanol extraction of lyophilized feces are reproducible and comprise a variety of different compounds including, among others, short-chain fatty acids (e.g. acetate, propionate, butyrate, isobutyrate, isovalerate, malate), organic acids (e.g. succinate, pyruvate, fumarate, lactate), amino acids, uracil, trimethylamine, ethanol, glycerol, glucose, phenolic acids, cholate, and lipid components. The NMR profiling approach was validated on fecal samples from a double-blinded, placebo-controlled, randomized cross-over study, in which healthy human subjects consumed a placebo and either a grape juice extract or a mix of grape juice and wine extract over a period of 4 weeks, each. The considerable inter- and intra-individual variability observed originates in the first instance from variable metabolite concentrations rather than from variable metabolite compositions, suggesting that different colonic flora share general biochemical characteristics metabolizing different substrates to specific metabolic patterns. Whereas the grape juice extract did not induce changes in the metabolite profiles as compared with the placebo, the mixture of grape juice and wine extract induced a reduction in isobutyrate, which may indicate that polyphenols are able to modulate the microbial ecology of the gut.

Mechanisms underlying the vasorelaxant effect induced by proanthocyanidin-rich fraction from Croton celtidifolius in rat small resistance arteries

Proanthocyanidins are condensed tannins present in fruits, vegetables, and flowers, consumed in the human diet. These compounds are believed to decrease coronary heart disease. The present study was designed to investigate the relaxing effects of a proanthocyanidin-rich fraction (PRF) obtained from Croton celtidifolius BAILL (Euphorbiaceae) barks in rat mesenteric arterial bed (MAB) and isolated mesenteric artery (MA). In the MAB pre-contracted with phenylephrine (Phe), PRF (0.1 - 100 microg) induced a concentration-dependent relaxation of 73% (compared to the control). This effect was significantly reduced by the nitric oxide (NO) synthase inhibitor N(omega)-nitro-L-arginine (L-NOARG) or high K(+) solution and completely abolished in vessels perfused with KCl plus L-NOARG. However, the vasorelaxant effect was not altered by indomethacin, atropine, yohimbine, pyrilamine, or K(+)-channel blockers: BaCl(2), glibenclamide, ouabain, and 4-aminopyridine. In isolated MA pre-contracted with Phe, PRF also induced a concentration-dependent relaxation (0.1 - 30 microg/mL), which was in turn inhibited by endothelial removal, guanylyl cyclase inhibitor 1H[1,2,3]oxadiazolo[4,3-alpha]quinoxalin, charybdotoxin (ChTx), and ChTx plus apamin. Moreover, the relaxant effect was not altered by HOE140 and apamin given alone. The present study demonstrates that the vasorelaxing effect of PRF is dependent upon the NO-cGMP pathway in combination with hyperpolarization due to activation of Ca(2+)-dependent K(+) channels.

Flavan-3-ols: nature, occurrence and biological activity

Representing the most common flavonoid consumed in the American diet, the flavan-3-ols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, whole and processed foods, herbal remedies and supplements. Their presence in food affects food quality parameters such as astringency, bitterness, sourness, sweetness, salivary viscosity, aroma, and color formation. The ability of flavan-3-ols to aid food functionality has also been established in terms of microbial stability, foamability, oxidative stability, and heat stability. While some foods only contain monomeric flavan-3-ols [(-)-epicatechin predominates] and dimeric proanthocyanidins, most foods contain oligomers of degree of polymerization values ranging from 1-10 or greater than 10. Flavan-3-ols have been reported to exhibit several health beneficial effects by acting as antioxidant, anticarcinogen, cardiopreventive, antimicrobial, anti-viral, and neuro-protective agents. This review summarizes the distribution and health effects of these compounds.

French maritime pine bark extract (Pycnogenol®) reduces thromboxane generation in blood from diabetic male rats

The protective effect of Pycnogenol against cardiovascular diseases was clearly demonstrated. Nevertheless, little is known about its antithrombotic effect, especially in diabetes associated with enhanced thromboxane synthesis leading to severe vascular complications. Therefore, the main purpose of our study was to evaluate the effect of long-term Pycnogenol intake on synthesis of prothrombotic thromboxane A(2) (TXA(2)) in animal model of insulin-dependent diabetes. The levels of main plasma TXA(2) metabolite, thromboxane B(2) (TXB(2)), were assessed by enzyme-linked immunosorbent assay. Diabetes was induced in Wistar male rats by single injection of streptozotocin, resulting after 8 weeks in significant body weight reduction, increased plasma glucose concentrations, and decreased plasma C-peptide levels, compared to non-diabetic animals. There was no significant reduction of plasma glucose concentrations after Pycnogenol ingestion. It was found, however, that daily administration of either Pycnogenol (5mg/kg b.wt.) or acetylsalicylic acid (ASA, 10mg/kg b.wt.) significantly reduced plasma TXB(2) concentrations, and this inhibitory effect was higher in the latter case. Nonetheless, simultaneous administration of Pycnogenol and ASA did not improve effectiveness of ASA-mediated decrease in TXB(2) generation. The results of the present study suggest that Pycnogenol might have a beneficial antithrombotic effect when administered alone or as a supplementation of standard antiplatelet therapy in diabetic patients.