Evaluation of peanut skin and grape seed extracts to inhibit growth of foodborne pathogens.

Peanut skin extract (PSE) and grape seed extract (GSE) are derived from waste products in the wine and peanut industries, respectively. Both have high concentrations of polyphenols, known to possess antioxidant and antimicrobial properties. PSE primarily contains "A-type" procyanidins, while GSE primarily contains "B-type" procyanidins. These differ structurally, but are both isomers of epicatechin dimers. The objective of this study was to evaluate the antimicrobial effects of PSE containing A-type procyanidins and GSE containing B-type procyanidins against select foodborne pathogens (Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium). The minimum inhibitory concentration (MIC) of the two extracts on L. monocytogenes, E. coli O157:H7, and S. Typhimurium was determined using the pour plate method. GSE had a significantly lower MIC (p ≤ .05) than PSE for L. monocytogenes (GSE = 60.6 ppm, PSE > 68.2 ppm) and S. Typhimurium (GSE = 45.7 ppm, PSE = 60.6 ppm), but no difference in inhibition of E. coli O157:H7. Since GSE contributed to greater inhibition, GSE extract was fractionated into monomer-rich (consisting primarily of catechins, epicatechins, and epicatechin gallates) and oligomer-rich (consisting of dimers, trimers, tetramers, up to decamers) components. Growth curves of all three pathogens in the presence of full extract, monomer and oligomer fractions were compared separately. None of the extracts inhibited S. Typhimurium growth. Generally, the extract containing greater oligomer components inhibited growth of L. monocytogenes and E. coli O157:H7 when compared to the control. Results indicate that an extract with type B procyanidins higher in oligomers may have greater antimicrobial properties.

Alterations to metabolically active bacteria in the mucosa of the small intestine predict anti-obesity and anti-diabetic activities of grape seed extract in mice.

Epidemiological and clinical studies suggest that grapes and grape-derived products may reduce the risk for chronic disease. Grape seed extract specifically has been gaining interest due to its reported ability to prevent weight gain, moderate hyperglycemia, and reduce inflammation. The purpose of this study was to examine the long-term effects of two doses of grape seed extract (10 and 100 mg kg-1 body wt per d in mice) on markers of metabolic syndrome in the context of a moderately high-fat diet. After 12 weeks, the lower dose of grape seed extract was more effective at inhibiting fat gain and improving glucose tolerance and insulin sensitivity. Neither the high fat diet nor grape seed extract altered skeletal muscle substrate metabolism. Most interestingly, when examining the profile of metabolically active microbiota in the mucosa of the small intestine, cecum, and colonic tissue, grape seed extract seemed to have the most dramatic effect on small intestinal tissue, where the population of Firmicutes was lower compared to control groups. This effect was not observed in the cecal or colonic tissues, suggesting that the main alterations to gut microbiota due to flavan-3-ol supplementation occur in the small intestine, which has not been reported previously. These findings suggest that grape seed extract can prevent early changes in glucose tolerance and alter small intestinal gut microbiota, prior to the onset of skeletal muscle metabolic derangements, when grape seed extract is consumed at a low dose in the context of a moderately high fat diet.

Monomeric cocoa catechins enhance ß-cell function by increasing mitochondrial respiration.

A hallmark of type 2 diabetes (T2D) is ß-cell dysfunction and the eventual loss of functional ß-cell mass. Therefore, mechanisms that improve or preserve ß-cell function could be used to improve the quality of life of individuals with T2D. Studies have shown that monomeric, oligomeric and polymeric cocoa flavanols have different effects on obesity, insulin resistance and glucose tolerance. We hypothesized that these cocoa flavanols may have beneficial effects on ß-cell function. INS-1 832/13-derived ß-cells and primary rat islets cultured with a monomeric catechin-rich cocoa flavanol fraction demonstrated enhanced glucose-stimulated insulin secretion, while cells cultured with total cocoa extract and with oligomeric or polymeric procyanidin-rich fraction demonstrated no improvement. The increased glucose-stimulated insulin secretion in the presence of the monomeric catechin-rich fraction corresponded with enhanced mitochondrial respiration, suggesting improvements in ß-cell fuel utilization. Mitochondrial complex III, IV and V components are up-regulated after culture with the monomer-rich fraction, corresponding with increased cellular ATP production. The monomer-rich fraction improved cellular redox state and increased glutathione concentration, which corresponds with nuclear factor, erythroid 2 like 2 (Nrf2) nuclear localization and expression of Nrf2 target genes including nuclear respiratory factor 1 (Nrf1) and GA binding protein transcription factor alpha subunit (GABPA), essential genes for increasing mitochondrial function. We propose a model by which monomeric cocoa catechins improve the cellular redox state, resulting in Nrf2 nuclear migration and up-regulation of genes critical for mitochondrial respiration, glucose-stimulated insulin secretion and ultimately improved ß-cell function. These results suggest a mechanism by which monomeric cocoa catechins exert their effects as an effective complementary strategy to benefit T2D patients.

High-molecular-weight cocoa procyanidins possess enhanced insulin-enhancing and insulin mimetic activities in human primary skeletal muscle cells compared to smaller procyanidins.

Dysregulation of glucose metabolism is a primary hallmark of metabolic disease (i.e., diabetes, obesity, etc.). Complementary nonpharmaceutical strategies are needed to prevent and/or ameliorate dysregulation of glucose metabolism and prevent progression from normoglycemia to prediabetes and type 2 diabetes across the lifespan. Cocoa compounds, particularly the procyanidins, have shown promise for improving insulin sensitivity and blood glucose homeostasis. However, the molecular mechanisms by which cocoa procyanidins exert these functions remain poorly understood. Furthermore, cocoa procyanidins exhibit size diversity, and evidence suggests that procyanidin bioactivity and size may be related. Here, we show that a procyanidin-rich cocoa extract elicits an antidiabetic effect by stimulating glycogen synthesis and glucose uptake, independent of insulin. Cocoa procyanidins did not appear to act via stimulation of AMPK or CaMKII activities. Additionally, in the presence of insulin, glycogen synthesis and AKT phosphorylation were affected. These mechanisms of action are most pronounced in response to oligomeric and polymeric procyanidins. These results demonstrate (1) specific mechanisms by which cocoa procyanidins improve glucose utilization in skeletal muscle and (2) that larger procyanidins appear to possess enhanced activities. These mechanistic insights suggest specific strategies and biological contexts that may be exploited to maximize the antidiabetic benefits of cocoa procyanidins.

Pan-colonic pharmacokinetics of catechins and procyanidins in male Sprague-Dawley rats.

Poor absorption and bioavailability of procyanidins from the upper gastrointestinal tract result in the majority of the dose reaching the colon. During colonic transit, progressive microbial metabolism likely produces gradients of procyanidins and microbial metabolites along the length of the colon, suggesting that proximal and distal regions are exposed to different profiles of procyanidins and metabolites. However, previous studies have largely treated the colon as a single organ or looked at fecal profiles, and differences in the profiles of native and metabolite compounds between regions have not been observed. The metabolism kinetics of procyanidins larger than trimers and formation of metabolites in the colon have not been well characterized. Therefore, the objective of this study was to determine the kinetics of delivery and microbial metabolism of monomeric, dimeric and oligomeric procyanidins in the cecum and proximal, mid and distal colon. Sprague-Dawley rats were gavaged grape seed extract and sacrificed over 18 h. Analysis of luminal contents showed distinct native and metabolite profiles for each region. Procyanidins had maximum concentrations at approximately 3h postgavage for all sections. Metabolites reached maximum concentrations from 3 to 18 h postgavage. The appearance of metabolites was highly dependent on species: larger metabolites were found at earlier times in the more proximal segments, and smaller metabolites were found at later times in more distal regions. This study allowed for the observation of regions in the lower gastrointestinal tract, giving insight into the distribution and delivery of procyanidins and their microbial metabolites throughout the colon.

Cocoa procyanidins with different degrees of polymerization possess distinct activities in models of colonic inflammation.

Procyanidins are available in the diet from sources such as cocoa and grapes. Procyanidins are unique in that they are comprised of repeating monomeric units and can exist in various degrees of polymerization. The degree of polymerization plays a role in determining the biological activities of procyanidins. However, generalizations cannot be made regarding the correlation between procyanidin structure and bioactivity because the size-activity relationship appears to be system dependent. Our aim was to screen fractions of procyanidins with differing degrees of polymerization in vitro for anti-inflammatory activities in models of colonic inflammation. Monomeric, oligomeric and polymeric cocoa procyanidin fractions were screened using cell models of disrupted membrane integrity and inflammation in human colon cells. High-molecular-weight polymeric procyanidins were the most effective at preserving membrane integrity and reducing secretion of interleukin-8 in response to inflammatory stimuli. Conversely, oligomeric procyanidins appeared to be the least effective. These results suggest that polymeric cocoa procyanidins may be the most effective for preventing loss of gut barrier function and epithelial inflammation, which are critical steps in the pathogenesis of metabolic endotoxemia, inflammatory bowel disease and colon cancer. Therefore, further investigations of the potential health-protective benefits of cocoa procyanidins with distinct degrees of polymerization, particularly high-molecular-weight procyanidins, are warranted.

Dietary supplementation with cocoa flavanols does not alter colon tissue profiles of native flavanols and their microbial metabolites established during habitual dietary exposure in C57BL/6J mice.

Metabolism of flavanols (catechins, procyanidins) by gut microbiota has been extensively characterized. Comparatively little is known about accumulation of flavanols and their metabolites in the colon tissues, particularly during chronic exposure to low doses. Mice were fed low doses of cocoa flavanols for 12 weeks. Supplementation of the control diet with flavanols did not increase colonic tissue accumulation of flavanols nor microbial metabolites versus control. The type of cocoa flavanols did not affect colonic tissue accumulation of native flavanols or metabolites. Total phenolic content of the diets indicated that these results are not explained by background levels of undetected phenolics in the control diet. This is the longest known chronic flavanol feeding study to examine colonic tissue accumulation. Vast differences appear to exist between acute high doses and chronic low doses, to which gut microbiota and epithelium adapt. These results indicate that the fate of flavanols in the colon during chronic exposure is not fully understood.

Characterization of the polyphenol composition of 20 cultivars of cider, processing, and dessert apples (Malus × domestica Borkh.) grown in Virginia.

Polyphenols and maturity parameters were determined in 20 apple cultivars with potential for hard cider production grown in Virginia, U.S.A. Concentrations of five classes of polyphenols were significantly different across cultivar for both peel and flesh. Total polyphenol concentration ranged from 0.9 µg/g wwb in flesh of Newtown Pippin to 453 µg/g wwb in peel of Red Delicious. Harrison, Granny Smith, Rome, Winesap, and Black Twig cultivars contained the highest concentration of total flavan-3-ols in flesh, indicating potential to impart desired astringency and bitterness to cider under processing conditions where extraction of polyphenols from peel is minimal. These results can inform selection of fruit juice, extracts, and byproducts for investigations of bioactivity and bioavailability of polyphenols, and provide baseline data for horticultural and processing research supporting the growing hard cider industry in Virginia. Based on these data, cultivars Harrison, Granny Smith, Rome, Winesap, and Black Twig show high potential for cider production in Virginia.

Simultaneous UPLC-MS/MS analysis of native catechins and procyanidins and their microbial metabolites in intestinal contents and tissues of male Wistar Furth inbred rats.

Procyanidins have been extensively investigated for their potential health protective activities. However, the potential bioactivities of procyanidins are limited by their poor bioavailability. The majority of the ingested dose remains unabsorbed and reaches the colon where extensive microbial metabolism occurs. Most existing analytical methods measure either native compounds (catechins and procyanidins), or their microbial metabolites. The objectives of this study were to develop a high-throughput extraction and UPLC-MS/MS method for simultaneous measurement of both native procyanidins and their metabolites, facilitating high-throughput analysis of native and metabolite profiles in various regions of the colon. The present UPLC-MS/MS method facilitates simultaneous resolution and detection of authentic standards of 14 native catechin monomers and procyanidins, as well as 24 microbial metabolites. Detection and resolution of an additional 3 procyanidin dimers and 10 metabolites for which standards were not available was achieved. Elution and adequate resolution of both native compounds and metabolites were achieved within 10min. The intraday repeatability for native compounds was between 1.1 and 16.5%, and the interday repeatability for native compounds was between 2.2 and 25%. Intraday and interday repeatability for metabolites was between 0.6 and 24.1% and 1 and 23.9%, respectively. Observed lower limits of quantification for native compounds were ∼9-350fmol on-column, and for the microbial metabolites were ∼0.8-12,000fmol on-column. Observed lower limits of detection for native compounds were ∼4.5-190fmol on-column, and for metabolites were 0.304-6020fmol on-column. For native monomers and procyanidins, extraction recoveries ranged from 38 to 102%. Extraction recoveries for the 9 microbial metabolites tested ranged from 41 to 95%. Data from tissue analysis of rats gavaged with grape seed extract indicate fairly high accumulation of native compounds, primarily monomers and dimers, in the cecum and colon. Metabolite data indicate the progressive nature of microbial metabolism as the digesta moves through the lower GI tract. This method facilitates the high-throughput, sensitive, and simultaneous analysis of both native compounds and their microbial metabolites in biological samples and provides a more efficient means of extraction and analysis than previous methods.

Oligomeric cocoa procyanidins possess enhanced bioactivity compared to monomeric and polymeric cocoa procyanidins for preventing the development of obesity, insulin resistance, and impaired glucose tolerance during high-fat feeding.

There is interest in the potential of cocoa flavanols, including monomers and procyanidins, to prevent obesity and type-2 diabetes. Fermentation and processing of cocoa beans influence the qualitative and quantitative profiles of individual cocoa constituents. Little is known regarding how different cocoa flavanols contribute to inhibition of obesity and type-2 diabetes. The objective of this study was to compare the impacts of long-term dietary exposure to cocoa flavanol monomers, oligomers, and polymers on the effects of high-fat feeding. Mice were fed a high-fat diet supplemented with either a cocoa flavanol extract or a flavanol fraction enriched with monomeric, oligomeric, or polymeric procyanidins for 12 weeks. The oligomer-rich fraction proved to be most effective in preventing weight gain, fat mass, impaired glucose tolerance, and insulin resistance in this model. This is the first long-term feeding study to examine the relative activities of cocoa constituents on diet-induced obesity and insulin resistance.

Chronic administration of dietary grape seed extract increases colonic expression of gut tight junction protein occludin and reduces fecal calprotectin: a secondary analysis of healthy Wistar Furth rats.

Animal studies have demonstrated the potential of grape seed extract (GSE) to prevent metabolic syndrome, obesity, and type 2 diabetes. Recently, metabolic endotoxemia induced by bacterial endotoxins produced in the colon has emerged as a possible factor in the etiology of metabolic syndrome. Improving colonic barrier function may control endotoxemia by reducing endotoxin uptake. However, the impact of GSE on colonic barrier integrity and endotoxin uptake has not been evaluated. We performed a secondary analysis of samples collected from a chronic GSE feeding study with pharmacokinetic end points to examine potential modulation of biomarkers of colonic integrity and endotoxin uptake. We hypothesized that a secondary analysis would indicate that chronic GSE administration increases colonic expression of intestinal tight junction proteins and reduces circulating endotoxin levels, even in the absence of an obesity-promoting stimulus. Wistar Furth rats were administered drinking water containing 0.1% GSE for 21 days. Grape seed extract significantly increased the expression of gut junction protein occludin in the proximal colon and reduced fecal levels of the neutrophil protein calprotectin, compared with control. Grape seed extract did not significantly reduce serum or fecal endotoxin levels compared with control, although the variability in serum levels was widely increased by GSE. These data suggest that the improvement of gut barrier integrity and potential modulation of endotoxemia warrant investigation as a possible mechanism by which GSE prevents metabolic syndrome and associated diseases. Further investigation of this mechanism in high-fat feeding metabolic syndrome and obesity models is therefore justified.