Wine Procyanidins Research Articles

Rapid optical method for procyanidins estimation in red wines

The present work outlines a reliable and rapid optical method to estimate tannin content in red wines. The method originates from the known reactivity of wine tannins (procyanidins) with proteinaceous matter (i.e. gelatin) which reaction results in a cloudiness due to the formation of floating procyanidin-protein complexes in solution. An optical device operating with a wavelength-sensitive pulsed electromagnetic source enabled to measure the extent of turbidity, combining the different intensity and spectral emission of a light source (tungsten lamp) with the photodiode wavelength sensitivity. In this experiment, 27 red wines (tannins content range: 6–1904 mg/L) were optically measured at the room temperature immediately after mixing with a saturated solution of gelatin in model wine buffer (12% ethanol, pH 3.5). An output signal waveform (voltage, V) was produced and modified as a function of peak intensity, amplitude and curvature depending on the extent of turbidity. The relationship was fitted obtaining a significant not-linear correlation (R2 up to 0.9657) with tannins content as determined using a reference colorimetric method. The proposed new optical method is easy and cost-effective and provides a reliable alternative to the time-consuming analyses for fast in-line and off-line analysis of procyanidins in wine.

Interaction between red wine procyanidins and salivary proteins: effect of stomach digestion on the resulting complexes

Some tannin(T)/SP complexes were disrupted by gastric digestion, leading to T release. This was seen for complexes formed with tannin mono-, di- and trimers. In contrast, complexes made by tetra- and pentamers were more resistant to gastric digestion.

Regulation of vascular endothelial function by red wine procyanidins: implications for cardiovascular health

The effects of oligomeric procyanidins (OPC) on vascular endothelial function provide a plausible explanation for the reduced incidence of coronary heart disease in red wine drinkers. Grape variety is an important influence on the amounts of OPC in wines. Red wines made from Aglianico, Sagrantino or Tannat grapes typically have higher OPC levels. The endothelial response to OPC induces atheroprotective changes in vascular function, which are likely mediated via oxidant signalling mechanisms originating from the mitochondrial electron transport chain.

Red wine interferes with oestrogen signalling in rat hippocampus

Oestrogens have neuroprotective properties, resulting in memory and learning preservation. Red wine (RW) has been linked to neuroprotection, but mechanisms are largely unknown. The aim of this work was to test the effect of RW or 13% ethanol solution consumption on the expression of aromatase and estrogen receptors (ER) in the rat hippocampus. Beverages were supplied to male Wistar rats and after 8 weeks of treatment animals were euthanised, hippocampus was removed, aromatase expression assessed by western blotting and aromatase and ER transcription determined by RT-PCR. The effects of treatments on hippocampal aromatase activity were also determined, as well as the effect of several red wine polyphenols in hippocampal homogenates from untreated animals. Aromatase transcription was increased by ethanol (to 158 ± 7%) but only significantly by RW (to 180 ± 9%). No difference was found in ERα expression among groups, whereas RW significantly decreased ERβ expression (to 63 ± 10%). Resveratrol, quercetin, myricetin and kaempferol had no effect on aromatase activity and catechin (300 μM), epicatechin (200 μM), procyanidin extract (200 mg/L) and fractioned procyanidins (FI and FII; 200 mg/L) significantly decreased aromatase activity. The contribution of procyanidins in wine to the effect observed in aromatase was investigated in animals treated for the same period with these compounds (200 mg/L), although no effect was seen in aromatase activity, mRNA or protein levels, meaning that this group of compounds had little contribution, if any, to the effects observed. Nevertheless, the increase in aromatase expression induced by RW may corroborate the neuroprotective ability attributed to this beverage. Alterations in the relative abundance of ER expression may also play an important role in the protection.

LDL Isolated from Plasma-Loaded Red Wine Procyanidins Resist Lipid Oxidation and Tocopherol Depletion

Dietary phenolic compounds may act as antioxidants in vitro, but because of structural modifications during absorption, its role based on concentrations high enough to afford an antioxidant protection needs to be re-evaluated. We have explored the hypothesis that red wine procyanidins interact with low density lipoproteins (LDL) and that, at this location, the phenolic compounds efficiently protect LDL from oxidation and maintain LDL alpha-tocopherol at a high steady state concentration by recycling it back from the alpha-tocopheroxyl radical. To this end, human plasma was supplemented with wine procyanidins and isolated LDL were challenged with a constant flux of peroxyl radicals. As compared with LDL from plasma-free procyanidins, those LDL better resisted lipid oxidation and exhibited longer lag-phases of alpha-tocopherol consumption. The procyanidins, depending on their structure, were able to reduce the UV-induced alpha-tocopherol radical in a micellar system, as evidenced by electron paramagnetic ressonance. Mechanistically, the protection of LDL was interpreted in terms of quenching of peroxyl radicals and the recycling of alpha-tocopherol by the procyanidins bound to the lipoproteins. These results support the notion that, in human plasma, the procyanidins, via binding to LDL, may act as efficient local antioxidants.

Red wine procyanidins and vascular health

Regular, moderate consumption of red wine is linked to a reduced risk of coronary heart disease and to lower overall mortality, but the relative contribution of wine's alcohol and polyphenol components to these effects is unclear. Here we identify procyanidins as the principal vasoactive polyphenols in red wine and show that they are present at higher concentrations in wines from areas of southwestern France and Sardinia, where traditional production methods ensure that these compounds are efficiently extracted during vinification. These regions also happen to be associated with increased longevity in the population.

Tandem mass spectrometry of the B-type procyanidins in wine and B-type dehydrodicatechins in an autoxidation mixture of (+)-catechin and (-)-epicatechin.

We describe the characterization of the B-type procyanidins in wine and the B-type dehydrodicatechins (dimeric flavan-3-ols) obtained for the autoxidation of (+)-catechin and (-)-epicatechin by tandem mass spectrometry (MS/MS) coupled to reversed-phase high-performance liquid chromatography (HPLC). The MS/MS analysis demonstrates that the interesting major fragments derive from the dissociations of the C-ring on the catechin or epicatechin unit, such as retro-Diels-Alder reactions. The two kinds of dimers give completely different fragmentations because of the striking effect of the C-C interflavan linkage (IFL). For the natural dimers in wine, a catechin or epicatechin unit linking to the C-4 position stabilizes the product ions by forming a large pi-pi hyperconjugated system, whereas a similar pi-pi system is formed within dehydrodicatechin B through the C-C IFL. Thus dissociation in MS/MS experiments was inhibited. Apparently, the fragmentations of the dimers differ from that of the monomer, which is very important in the study of the gas-phase ion behaviour of the polymeric flavan-3-ols. In addition, two specific fragment ions at m/z 451 for native dimers and at m/z 393 for autoxidation species in HPLC/MS/MS were found to be very useful for analysing mixtures of B-type procyanidins and B-type dehydrodicatechins in food and beverages.

Wine Polyphenols and Optimal Nutrition

One of the key elements of Mediterranean diet is the use of wine, usually taken with foods. Besides the evidence from human experience and ancient medicine, modern experimental data support the notion that the most striking effect of wine in protecting against cardiovascular disease involves the reduction of oxidative damage to plasma lipoproteins. This oxidative damage is thought to be mediated by eating foods containing oxidized lipids. In fact, eating a meal containing oxidized lipids increases the plasma level of lipid hydroperoxides and increases the susceptibility to oxidation of LDL. The postprandial increase of LDL-, an oxidatively modified form of LDL, where apoB is unfolded and sinking in the core of the particle, is a valuable biomarker for this food-derived oxidative stress in plasma. Wine, taken with foods minimizes the postprandial rise of lipid hydroperoxides and LDL- and abolishes the increase of LDL oxidability. Among wine antioxidants, the best candidates for providing an antioxidant effect are procyanidins. These compounds are considered better antioxidants than the corresponding monomers containing catechol groups. This is due to the hydrogen transfer mechanism for the radical-scavenging reaction, which renders the reaction more specific for peroxyl radicals and pH independent. Moreover, the fast intramolecular disproportion among aroxyl radicals pulls the antioxidant reaction by both decreasing the oxidation potential and increasing the rate of the reaction. Apparently, wine procyanidins are active in preventing lipid oxidation of foods while in the digestive tract, thus preventing the postprandial plasma rise in oxidants. The likely limited bioavailability of these compounds, therefore, does not affect their relevance as key elements for optimizing nutrition and reducing risk of atherogenesis. Accordingly, studies with rabbits fed a high cholesterol diet show that grapeseed procyanidins are strongly protective not only in terms of reducing plasma lipid peroxides, but they also markedly inhibit lipid-laden foam-cell deposition. Drinking wine at meals provides this kind of protection, and the final benefits are realized by the prevention of the development of atheromatous lesions even under conditions of hypercholesterolemia.

Human apo A-I and rat transferrin are the principal plasma proteins that bind wine catechins.

The processes of absorption, blood transport, tissular distribution, metabolism, and excretion are at present understood very little. The aim of this study was to investigate blood transport and identify which principal plasma proteins in humans and rats bind to monomeric catechin and procyanidins in red wine ex vivo. Human and rat plasma and serum were incubated with (+)-catechin and procyanidins from grape seed, the origin of red wine catechins. Proteins were separated by SDS-PAGE and native-PAGE to determine which proteins bound to these compounds. The principal protein that bound to (+)-catechin in each species was sequenced. SDS-PAGE showed that (+)-catechin and procyanidins mainly bound to a protein of about 80 kDa in rats and 35 kDa in humans. Their sequencing indicated that these proteins were apo A-I in humans and transferrin in rats. The fact that red wine procyanidins bind to both proteins suggests that they may have a role in reverse cholesterol transport and in the oxidizing action of iron.

Separation and quantitative determination of grape and wine procyanidins by high performance reversed phase liquid chromatography

AbstractA method is described for the separation and quantitative analysis of procyanidins in grape and wine. On a polyamide chromatographic column an initial elution with water at pH 7.0 enabled elimination of interfering phenolic acids. A second elution with acetonitrile/water (30:70 v) was performed to extract catechins. A third elution with acetone/water (75:25 v) was carried out to obtain procyanidins. The quantitative determination of procyanidins was done by high performance reversed phase liquid chromatography. The HPLC analysis was brought down to ∼55 min. The method is accurate and reproducible and has an acceptable extraction efficiency.