Current research on dietary antioxidants misses the so-called non-extractable polyphenols (NEPP), which are not significantly released from the food matrix either by mastication, acid pH in the ...stomach or action of digestive enzymes, reaching the colon nearly intact. NEPP, not detected by the usual analytical procedures, are made up of macromolecules and single phenolic compounds associated with macromolecules. Therefore, NEPP are not included in food and dietary intake data nor in bioavailability, intervention or observational studies. The present paper aims to provide an overview of dietary NEPP - nature, occurrence in diet, metabolic fate and possible health effects. NEPP are a relevant fraction of dietary polyphenols exerting their main biological action in the colon, where they are extensively fermented by the action of microbiota, giving place to absorbable metabolites. NEPP exhibit different potential health-related properties, in particular in relation to gastrointestinal health, such as increases in antioxidant and antiproliferative capacities, reduction of intestinal tumorigenesis and modification of gene expression, as observed in different animal models. Further research into NEPP may provide a better understanding of the health effects of dietary antioxidants.
Abstract Objective The objective of the study was to evaluate the effects of a grape product rich in dietary fiber and natural antioxidants on cardiovascular disease risk factors. Methods A ...randomized, controlled parallel-group trial was carried out. Thirty-four non-smoking (21 normocholesterolemic and 13 hypercholesterolemic) adults were supplemented for 16 wk with 7.5 g/d of grape antioxidant dietary fiber, a natural product containing 5.25 g of dietary fiber and 1400 mg of polyphenols. Nine non-supplemented non-smokers were followed as a control group. Fasting blood samples, blood pressure, and anthropometric readings were obtained at baseline and at week 16. Subjects were allowed to consume their regular diet, which was monitored weekly. Results Grape antioxidant dietary fiber (7.5 g/d) reduced significantly ( P < 0.05) total cholesterol (9%), low-density lipoprotein cholesterol (9%), and systolic and diastolic blood pressures (6% and 5% respectively). Greater reductions in total cholesterol (14.2%) and low-density lipoprotein cholesterol (11.6%, P < 0.05) were observed in hypercholesterolemic subjects. No changes were observed in the control group. There was a reduction of 2.5 points in the Framingham Global Risk Score in the supplemented group. A significant reduction in triacylglycerol concentration took place in the supplemented hypercholesterolemic subjects (18.6%, P < 0.05). Conclusion Grape antioxidant dietary fiber showed significant reducing effects in lipid profile and blood pressure. The effects appear to be higher than the ones caused by other dietary fibers, such as oat fiber or psyllium, probably due to the combined effect of dietary fiber and antioxidants.
The comparison between antioxidant capacity values reported by different laboratories is quite difficult because of substantial differences in sample preparation, extraction of antioxidants and ...expression of results. An updated methodology to determine of antioxidant capacity in plant foods, oils and beverages – including extraction of antioxidants, measurement of antioxidant capacity and expression of results – is presented. During sample preparation, loss of antioxidants in drying and milling steps must be minimized. Antioxidant capacity is determined in aqueous-organic extracts (combining at least two extraction cycles) and in the corresponding residues (acidic hydrolyzates to release condensed proanthocyanidins and hydrolyzable phenolics). Different aspects, such as type of solvent and possible interferences form non-antioxidant compounds, that may affect the results of the most common methods of antioxidant capacity (FRAP, ABTS, DPPH and ORAC) are discussed. The different ways of expressing antioxidant capacity results, including kinetic parameters, are described.
Epidemiological and clinical studies show that diets with a high antioxidant capacity, such us those rich in plant food and beverages, are associated with significant decreases in the overall risk of ...cardiovascular disease or colorectal cancer. Current studies on dietary antioxidants and dietary antioxidant capacity focus exclusively on low molecular weight or soluble antioxidants (vitamins C and E, phenolic compounds and carotenoids), ignoring macromolecular antioxidants. These are polymeric phenolic compounds or polyphenols and carotenoids linked to plant food macromolecules that yield bioavailable metabolites by the action of the microbiota with significant effects either local and/or systemic after absorption. This study determined the antioxidant capacity of the Spanish Mediterranean diet including for the first time both soluble and macromolecular antioxidants. Antioxidant capacity and consumption data of the 54 most consumed plant foods and beverages were used. Results showed that macromolecular antioxidants are the major dietary antioxidants, contributing a 61 % to the diet antioxidant capacity (8000 μmol Trolox, determined by ABTS method). The antioxidant capacity data for foods and beverages provided here may be used to estimate the dietary antioxidant capacity in different populations, where similar contributions of macromolecular antioxidants may be expected, and also to design antioxidant-rich diets. Including macromolecular antioxidants in mechanistic, intervention and observational studies on dietary antioxidants may contribute to a better understanding of the role of antioxidants in nutrition and health.
The analytical dietary fiber (DF) methods most widely used today were developed to determine non-starch polysaccharides and lignin. Updated dietary fiber definition includes all indigestible plant ...food constituents. Recent methods have proposed the measurement of resistant starch and oligosaccharides, but other major indigestible constituents such as polyphenolic compounds and resistant protein are still omitted in dietary fiber analysis. There is scientific evidence that an appreciable amount of dietary polyphenols are associated with the dietary fiber matrix, being a fermentable substrate for bacterial microflora. The objective of this work was to show polyphenols compounds are major constituents of dietary fiber and to propose a procedure for their measurement. Results showed that polyphenols are major constituents of DF, accounting from 1.4% to 50.7% (dry weight) of insoluble dietary fiber in plant foods and from 2.9% to 62.8% of soluble dietary fiber in common beverages.
Patient-derived induced pluripotent stem cells (iPSCs) provide a powerful tool for identifying cellular and molecular mechanisms of disease. Macular telangiectasia type 2 (MacTel) is a rare, ...late-onset degenerative retinal disease with an extremely heterogeneous genetic architecture, lending itself to the use of iPSCs. Whole-exome sequencing screens and pedigree analyses have identified rare causative mutations that account for less than 5% of cases. Metabolomic surveys of patient populations and GWAS have linked MacTel to decreased circulating levels of serine and elevated levels of neurotoxic 1-deoxysphingolipids (1-dSLs). However, retina-specific, disease-contributing factors have yet to be identified. Here, we used iPSC-differentiated retinal pigmented epithelial (iRPE) cells derived from donors with or without MacTel to screen for novel cell-intrinsic pathological mechanisms. We show that MacTel iRPE cells mimicked the low serine levels observed in serum from patients with MacTel. Through RNA-Seq and gene set enrichment pathway analysis, we determined that MacTel iRPE cells are enriched in cellular stress pathways and dysregulation of central carbon metabolism. Using respirometry and mitochondrial stress testing, we functionally validated that MacTel iRPE cells had a reduction in mitochondrial function that was independent of defects in serine biosynthesis and 1-dSL accumulation. Thus, we identified phenotypes that may constitute alternative disease mechanisms beyond the known serine/sphingolipid pathway.
ABSTRACT Valacyclovir, enzymatically hydrolyzed in the body to acyclovir, is a guanine‐based nucleoside analog commonly prescribed as an antiviral therapy. Previous reports suggest that guanosine ...analogs bind to guanine deaminase; however, it is unclear whether they act as inhibitors or substrates. Data from our laboratory suggest that inhibition of guanine deaminase by small molecules attenuates spinal cord injury‐induced neuropathic pain. Here, we examine whether the guanosine analogs valacyclovir and acyclovir are deaminated by cypin ( cy tosolic P SD‐95 in teractor), the major guanine deaminase in the body, or if they act as cypin inhibitors. Using purified Rattus norvegicus cypin, we use NADH‐coupled assay to confirm deamination of valacyclovir and determined Michaelis–Menten constants. Subsequently, we use tryptophan fluorescence quenching assay to calculate dissociation constants for valacyclovir and acyclovir and find that inclusion of the valine motif in valacyclovir increases affinity for cypin compared to acyclovir. To our knowledge, neither K m nor K D values for cypin has been previously reported for either compound. We use Amplex Red assay and demonstrate that both valacyclovir and acyclovir are cypin substrates and that their metabolites are further processed by xanthine oxidase and uricase. Using molecular dynamics simulations, we demonstrate that an alpha helix near the active site is displaced when valacyclovir binds to cypin. Furthermore, we used LC–MS‐based assay to directly confirm deamination of valacyclovir by cypin. Taken together, our results demonstrate a novel role for cypin in deamination of valacyclovir and acyclovir and suggest that therapeutics based on purine structures may be inactivated by cypin, decreasing inhibitory efficacy.
An improvement in oxidative status is associated with a reduction in the incidence of several chronic diseases. However, daily intake of antioxidants in Western diets is decreasing. This study ...evaluates the effect of daily consumption of an antioxidant-rich juice (ARJ) on oxidative status, cardiovascular disease risk parameters, and untargeted plasma and urine metabolomes. Twenty-eight healthy young adults participated in an 8-week clinical trial by drinking 200 mL of ARJ (pomegranate and grape) daily. At the end of the study, the subjects showed a significant decrease (−29 %) in plasma lipid oxidation (malondialdehyde concentration), and a significant increase (+115 %) in plasma antioxidant capacity. Plasma and urine metabolomes were also significantly modified and some ions modified in urine were identified, including metabolites of polyphenols, ascorbic acid and biliary acids. No significant changes were observed in lipid profile, inflammation, blood pressure or glycaemia. These results show that incorporating antioxidant-rich beverages into common diets may improve oxidative status in healthy subjects.
Most studies on bioavailability of phenolic antioxidants are focused in foods and beverages in which they may be easily released from the food matrix, reaching a peak in plasma antioxidant capacity ...1-2 h after the intake. However, plant foods contain significant amounts of polyphenols associated with dietary fiber. The aim of the present work was to seek the bioavailability of total phenolic antioxidants associated with dietary fiber by measuring plasma antioxidant capacity in human volunteers. An acute intake of 15 g of a dietary fiber rich in associated phenolic antioxidants in healthy volunteers (n = 10) increased antioxidant capacity of plasma in relation to a control group (n = 4), becoming significant 8 h after the intake. This shows that phenolic antioxidants associated with dietary fiber are at least partially bioavailable in humans, although dietary fiber appears to delay their absorption. No significant changes were observed after long-term intake (16 weeks, 34 subjects).