Characterization of protein-polyphenol interactions

Dietary polyphenols have received attention for their biologically significant functions as antioxidants, anticarcinogens or antimutagens, which have led to their recognition as potential nutraceuticals. Polyphenols also characteristically possess a significant binding affinity for proteins, which can lead to the formation of soluble and insoluble protein-polyphenol complexes. Questions remain concerning whether and to what extent the protein-polyphenol interaction influences functionality. For example, is the formation of protein-polyphenol complexes an obstacle to the nutritional bioavailability of either species? This article discusses the development of suitable methodologies to investigate the physicochemical basis of protein-polyphenol interactions and the influence of structure-activity relationships on binding affinities. (C) 2003 Elsevier Ltd. All rights reserved.

A study of the antioxidant capacity of oak wood used in wine ageing and the correlation with polyphenol composition

The antioxidant capacity of oak wood used in the ageing of wine was studied by four different methods: measurement of scavenging capacity against a given radical (ABTS, DPPH), oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP). Although, the four methods tested gave comparable results for the antioxidant capacity measured in oak wood extracts, the ORAC method gave results with some differences from the other methods. Non-toasted oak wood samples displayed more antioxidant power than toasted ones due to differences in the polyphenol compositon. A correlation analysis revealed that ellagitannins were the compounds mainly responsible for the antioxidant capacity of oak wood. Some phenolic acids, mainly gallic acid, also showed a significant correlation with antioxidant capacity.

Effect of cultivar type and ripening on the polyphenol content of date palm fruit

Date palm (Pheonix dactylifera) fruit contains an array of polyphenols, although how these levels alter with cultivar type and fruit ripening is unclear. Utilizing HPLC and LC-ESI-MS/MS, this study define and quantify an array of hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids in three common cultivars of dates (Ajwa, Barni, and Khalas) at the main ripening stages (kimri, khalal, rutab, and tamr). Polyphenols were at highest concentration at earlier stages of ripening, with concentrations reducing with ripening. The khalal stage of the Ajwa cultivar contained significantly higher (P < 0.001) levels of polyphenols than measured in the Barni and Khalas dates at the same degree of ripening. Furthermore, the Ajwa cultivar was the only one to contain significant quantities of anthocyanidins, in particular at the khalal stage. These data suggest dates are a significant source of polyphenols, especially if the earlier edible ripening stages are consumed or utilized as food ingredients.

The effects of flavonoid and other polyphenol consumption on cognitive performance: A systematic research review of human experimental and epidemiological studies

Literature reviews suggest flavonoids, a sub-class of polyphenols, are beneficial for cognition. This is the first review examining the effect of consumption of all polyphenol groups on cognitive function. Inclusion criteria were polyphenol vs. control interventions and epidemiological studies with an objective measure of cognitive function. Participants were healthy or mildly cognitively impaired adults. Studies were excluded if clinical assessment or diagnosis of Alzheimer’s disease, dementia, or cognitive impairment was the sole measure of cognitive function, or if the polyphenol was present with potentially confounding compounds such as caffeine (e.g. tea studies) or Ginkgo Biloba. 28 studies were identified; 4 berry juice studies, 4 cocoa studies, 13 isoflavone supplement studies, 3 other supplement studies, and 4 epidemiological surveys. Overall, 16 studies reported cognitive benefits following polyphenol consumption. Evidence suggests that consuming additional polyphenols in the diet can lead to cognitive benefits, however, the observed effects were small. Declarative memory and particularly spatial memory appear most sensitive to polyphenol consumption and effects may differ depending on polyphenol source. Polyphenol berry fruit juice consumption was most beneficial for immediate verbal memory, whereas isoflavone based interventions were associated with significant improvements for delayed spatial memory and executive function. Comparison between studies was hampered by methodological inconsistencies. Hence, there was no clear evidence for an association between cognitive outcomes and polyphenol dose response, duration of intervention, or population studied. In conclusion, however, the findings do imply that polyphenol consumption has potential to benefit cognition both acutely and chronically.

Comparison of in vivo and in vitro digestion on polyphenol composition in lingonberries: potential impact on colonic health

The composition of polyphenols in ileal fluid samples obtained from an ileostomy subject after lingonberry intake was compared with lingonberry extracts obtained after simulated in vitro digestion (IVDL) and subsequent faecal fermentation (IVFL). HPLC-PDA-MS/MS analysis confirmed similar patterns of lingonberry (poly)phenolic metabolism after the in vivo and in vitro digestion, with reduced recovery of anthocyanins and a similar pattern of recovery for proanthocyanidins observed for both methods of digestion. On the other hand, the IVFL sample contained none of the original (poly)phenolic components but was enriched in simple aromatic components. Digested and fermented extracts exhibited significant (P < 0.05) anti-genotoxic (Comet assay), anti-mutagenic (Mutation Frequency assay), and anti-invasive (Matrigel Invasion assay) effects in human cell culture models of colorectal cancer at physiologically-relevant doses (0-50 μg/mL gallic acid equivalents). The ileal fluid induced significant anti-genotoxic activity (P < 0.05), but at a higher concentration (200 μg/mL gallic acid equivalents) than the IVDL. Despite extensive structural modification following digestion and fermentation, lingonberry extracts retained their bioactivity in vitro. This reinforces the need for studies to consider the impact of digestion when investigating bioactivity of dietary phytochemicals.

Decomposition and phosphorus release from organic residues as affected by residue quality and added inorganic phosphorus

The combined use of organic residue and inorganic fertiliser-phosphorus (P) is appropriate in meeting both the short and long-term P requirement of crops. To assess the influence of added inorganic fertiliser-P on the processes of decomposition and P release from the residue and the relationships with quality, prunings of Gliricidia sepium, Leucaena leucocephela, Senna siamea, Acacia mangium and Paraserienthus falcataria were incubated without and with added inorganic fertiliser-P for 56 days. Soil was added only as inoculum. Decomposition rate and amounts of acid extractable-P (P release) were in the same order: G. sepium > S. siamea > L. leucocepheta > P falcataria > A. mangium. Unlike the other residues, A. mangium released no P despite the loss of half its mass during the 8 weeks of incubation. The residue P content correlated with P release. However, decomposition rate did not correlate with residue P content but with the lignin, polyphenol and cellulose content, and ratios to P. These ratios were negatively correlated with P release suggesting that lignin and polyphenol contents influence P release more when the residue-P content is low. Results suggest that rate of decomposition influences the release of P. The critical residue P content for P release was estimated to be 0.12% < P < 0.19%. Added P had no effect on decomposition and P release from the residues.

The role of polyphenolic compounds in the diet as inhibitors of platelet function

Platelets play a substantial role in cardiovascular disease, and for many years there has been a search for dietary components that are able to inhibit platelet function and therefore decrease the risk of cardiovascular disease. Platelets can be inhibited by alcohol, dietary fats and some antioxidants, including a group of compounds, the polyphenols, found in fruits and vegetables. A number of these compounds have been shown to inhibit platelet function both in vitro and in vivo. In the present study the effects of the hydroxycinnamates and the flavonoid quercetin on platelet activation and cell signalling in vitro were investigated. The hydroxycinnamates inhibited platelet function, although not at levels that can be achieved in human plasma by dietary intervention. However, quercetin inhibited platelet aggregation at levels lower than those previously reported. Quercetin was also found to inhibit intracellular Ca mobilisation and whole-cell tyrosine protein phosphorylation in platelets, which are both processes essential for platelet activation. The effect of polyphenols on platelet aggregation in vivo was also investigated. Twenty subjects followed a low-polyphenol diet for 3 d before and also during supplementation. All subjects were supplemented with a polyphenol-rich meal every lunchtime for 5 d. Platelet aggregation and plasma flavonols were measured at baseline and after 5 d of dietary supplementation. Total plasma flavonoids increased significantly after the dietary intervention period (P = 0.001). However, no significant changes in ex vivo platelet aggregation were observed. Further investigation of the effects of individual polyphenolic compounds on platelet function, both in vitro and in vivo, is required in order to elucidate their role in the relationship between diet and the risk of cardiovascular disease.

Inhibition of the formation of the neurotoxin 5-S-cysteinyl-dopamine by polyphenols

The death of nigral neurons in Parkinson's disease is thought to involve the formation of the endogenous neurotoxin, 5-S-cysteinyl-dopamine. In the present study, we show that the polyphenols, (+)-catechin and caffeic acid, which contain a catechol moiety, inhibit tyrosinase-induced formation of 5-S-eysteinyl-dopamine via their capacity to undergo tyro sina se-induced oxidation to yield cysteinyl-polyphenol adducts. In contrast, the inhibition afforded by the flavanone, hesperetin, was not accompanied by the formation of cysteinyl-hesperetin adducts, indicating that it may inhibit via direct interaction with tyrosinase. Whilst the stilbene resveratrol also inhibited 5-S-eysteinyl-dopamine formation, this was accompanied by the formation of dihydrobenzothiazine, a strong neurotoxin. Our data indicate that the inhibitory effects of polyphenols against 5-S-cysteinyl-dopamine formation are structure-dependent and shed further light on the mechanisms by which polyphenols exert protection against neuronal injury relevant to neurodegenerative diseases. (C) 2007 Elsevier Inc. All rights reserved.

Champagne wine polyphenols protect primary cortical neurons against peroxynitrite-induced injury

White wines are generally low in polyphenol content as compared to red wines. However, Champagne wines have been shown to contain relatively high amounts of phenolic acids that may exert protective cellular actions in vivo. In this study, we have investigated the potential neuroprotective effects of Champagne wine extracts, and individual phenolics present in these extracts, against peroxynitrite-induced injury. Organic and aqueous Champagne wine extracts exhibited potent neuroprotective activity against peroxynitrite-induced injury at low concentrations (0.1 mu g/mL). This protection appeared to be in part due to the cellular actions of individual components found in the organic extracts, notably tyrosol, caffeic acid, and gallic acid. These phenolics were observed to exert potent neuroprotection at concentrations between 0.1 and 10 mu M. Together, these data suggest that polyphenols present in Champagne wine may induce a neuroprotective effect against oxidative neuronal injury.

Post-genomics approaches towards monitoring changes within the microbial ecology of the gut

The human gut microbiota, comprising many hundreds of different microbial species, has closely co-evolved with its human host over the millennia. Diet has been a major driver of this co-evolution, in particular dietary non-digestible carbohydrates. This dietary fraction reaches the colon and becomes available for microbial fermentation, and it is in the colon that the great diversity of gut microorganisms resides. For the vast majority of our evolutionary history humans followed hunter-gatherer life-styles and consumed diets with many times more non-digestible carbohydrates, fiber and whole plant polyphenol rich foods than typical Western style diets today.

Biomarkers of the intake of dietary polyphenols: strengths, limitations and application in nutrition research

In order to establish firm evidence for the health effects of dietary polyphenol consumption, it is essential to have quantitative information regarding their dietary intake. The usefulness of the current methods, which rely mainly on the assessment of polyphenol intake using food records and food composition tables, is limited as they fail to assess total intake accurately. This review highlights the problems associated with such methods with regard to polyphenol-intake predictions. We suggest that the development of biological biomarkers, measured in both blood and urine, are essential for making accurate estimates of polyphenol intake. However, the relationship between dietary intakes and nutritional biomarkers are often highly complex. This review identifies the criteria that must be considered in the development of such biomarkers. In addition, we provide an assessment of the limited number of potential biomarkers of polyphenol intake currently available.

Critical stages of the brewing process for changes in antioxidant activity and levels of phenolic compounds in ale

Samples were taken at each stage of brewing (malt, milling, mashing, wort separation, hop addition, boiling, whirlpool, dilution, fermentation, warm rest, chill-lagering, beer filtration, carbonation and bottling, pasteurization, and storage). The level of antioxidant activity of unfractionated, low-molecular-mass (LMM) and high-molecular-mass (HMM) fractions was measured by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfortic acid) radical cation (ABTS(.+)) and ferric-reducing antioxidant power (FRAP) procedures. Polyphenol levels were assessed by HPLC. The LMM fraction (<5 kDa) was responsible for similar to80% of the level of antioxidant activity of the unfractionated malt and beer samples. In the unfractionated samples, significant decreases (P < 0.001) in antioxidant activity levels were observed after milling and beer filtration, with the decrease after beer filtration being accompanied by a significant decrease (P > 0.001) in catechin and ferulic acid levels. Increases in antioxidant activity levels were observed after mashing, boiling, fermentation, chill-lagering, and pasteurization, in line with previous studies on lager. Additionally, increases in the level of antioxidant activity occurred after wort separation and carbonation and bottling and were accompanied by increases in levels of most monitored polyphenols. Data from the ABTS(.-) and FRAP assays indicated that the compounds contributing to the levels of antioxidant activity responded differently in the two procedures. Levels of ferulic, vanillic, and chlorogenic acids and catechin accounted for 45-61% of the variation in antioxidant activity levels.

Antioxidant and antimicrobial activities of tea infusions

Tea polyphenols, especially the catechins, are potent antimicrobial and antioxidant agents, with positive effects on human health. White tea is one of the less studied teas but the flavour is more accepted than that of green tea in Europe. The concentrations of various catechins in 13 different kinds of infusion were determined by capillary electrophoresis. The total polyphenol content (Folin-Ciocalteu method), the trolox equivalent antioxidant capacity (TEAC value determined with the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation) and the inhibitory effects of infusions on the growth of some microorganisms were determined. Five different infusions (black, white, green and red teas and rooibos infusion) were added to a model food system, comprising a sunflower oil-in-water emulsion containing 0% or 0.2% bovine serum albumin (BSA), and the oxidative stability was studied during storage at 37 degrees C. Oxidation of the oil was monitored by determination of the peroxide value. The highest radical-scavenging activity observed was for the green and white teas. Emulsions containing these extracts from these teas were much more stable during storage when BSA was present than when it was not present, even though BSA itself did not provide an antioxidant effect (at 0.2% concentration). Rooibos infusion did not show the same synergy with BSA. Green tea and white tea showed similar inhibitions of several microorganisms and the magnitude of this was comparable to that of the commercial infusion 2 (C.I.2), "te de la belleza". This tea also had an antioxidant activity comparable to green tea. (C) 2007 Published by Elsevier Ltd.