Flavonols In Wines Research Articles

Grapevine red blotch virus alters grape skin cell-wall composition impacting phenolic extractability during winemaking.

Grapevine red blotch virus (GRBV) is the causal agent of grapevine red blotch disease and is known to delay grape ripening. However, grape cell-wall modifications during GRBV infection are largely unknown, even though the cell wall plays a large role in pathogenicity, viral interactions with host plants, and phenolic extractability during winemaking. Understanding the impact of GRBV infection on cell-wall metabolism is important for the development of potential mitigations strategies. In this study, high-throughput transcriptome sequencing was conducted on Vitis vinifera L. 'Merlot' grapes during ripening. The cell-wall composition, phenolic content, and phenolic extractability at two different commercial harvest points were also determined. Log fold changes indicated a strong induction in diseased grapes at harvest of several transcripts involved in cell-wall solubilization and degradation. However, these observations did not translate to changes in cell-wall composition at either harvest point in diseased grapes, potentially suggesting post-transcriptional regulation. Moderate induction of pectin methylesterase inhibitor transcripts and transcripts associated with pathogenesis-related proteins coincided with increases in pectin and soluble proteins in cell walls of diseased grapes at harvest. Both pectin and pathogenesis-related proteins are known to retain phenolic compounds during winemaking. Our study corroborates this finding when the percentage extractability of flavonols in wines was significantly lower when made from GRBV-infected fruit. These results suggest GRBV alters the grape cell walls, consequently decreasing phenolic extraction during winemaking. © 2023 Society of Chemical Industry.

Manipulating the severe shoot topping delays the harvest date and modifies the flavor composition of Cabernet Sauvignon wines in a semi-arid climate

This study aimed to mitigate the adverse effects of global warming by applying severe shoot topping (SST) to grapevines in a semi-arid climate. A three-year study (2018–2020) was performed to investigate the impact of SST on wine flavor composition. Results showed that SST effectively delayed the grape harvest date, which was more evident in the dry and warm vintage (7–11 d). SST significantly increased the concentration of myricetin-based flavonols in wines which were 18% higher than in untreated wines. Through orthogonal partial least squares discriminant analysis (OPLS-DA), SST wines were characterized by more abundant phenolic compounds and higher sensory scores. The carry-over effect of applying SST in consecutive years in the same vines could be reflected in wine color. The correlations among wine metabolites, color and aroma parameters, and sensory parameters were evaluated through multiple analyses. This study provided an idea for delaying grape ripening in a semi-arid climate.

Precipitation before Flowering Determined Effectiveness of Leaf Removal Timing and Irrigation on Wine Composition of Merlot Grapevine.

Grapevine productivity, and berry and wine flavonoid concentration, depend on the interactions of cultivar, environment, and applied cultural practices. We characterized the effects that mechanical leaf removal and irrigation treatments had on the flavonoid concentration of ‘Merlot’ (Vitis vinifera, L.) grape berries and wines in a hot climate over two growing seasons with contrasting precipitation patterns. Leaves were removed by machine, either at prebloom (PBLR), or at post-fruit-set (PFLR), or not removed (control) and irrigation was either applied as sustained deficit irrigation (SDI) at 0.8 of crop evapotranspiration (ETc) from budbreak to fruit set, or regulated deficit irrigation (RDI) at 0.8 ETc from bud break to fruit set, 0.5 ETc from fruit set to veraison, and 0.8 ETc from veraison to harvest, of ETc In 2014, PFLR reduced the leaf area index (LAI) compared to control. The RDI decreased season-long leaf water potential (ΨInt) compared to SDI. However, in 2015, none of the treatments affected LAI or ΨInt. In 2014, berry flavonoid concentrations were reduced by PBLR as well as SDI. SDI increased the flavonoid concentrations in wine, and PFLR increased some wine flavonols in one season. No factor affected the concentrations of wine proanthocyanidins or mean degree of polymerization. Thus, mechanical PFLR and RDI may increase berry flavonoid accumulation without yield reduction, in red wine grapes cultivars grown in hot climates when precipitation after bud break is lacking. However, spring precipitation may influence the effectiveness of these practices as evidenced by this work in a changing climate.

New acylated flavonols identified in Vitis vinifera grapes and wines

Flavonols are a class of polyphenol compounds whose importance for wine quality has increased as their structures and properties have become better understood. Here, the acetylated and p-coumaroylated derivatives of the flavonol 3-O-glucosides of isorhamnetin, laricitrin and syringetin have been identified for the first time in Vitis vinifera grape skins and wines. First, the MS2 fragmentation patterns of the new flavonol derivatives showed a main signal attributable to the expected flavonol aglycone. In the p-coumaroylated derivatives, the signal corresponding to the intermediate loss of the phenolic acid was also observed. The structures of the aglycones were confirmed by their respective MS3 experiments that matched with those obtained from authentic standards of the aglycones. In addition, the fragmentation signals corresponding to the aglycone radical ions generated through homolytic cleavage assisted identification, and could support future studies of flavonoid compounds by ESI-MS. Using an HPLC-ESI-Q-ToF system, the observed m/z values of the compounds being studied were successfully matched with the expected formula. Surprisingly, just the minority methoxylated flavonol glucosides presented acylation, suggesting a high substrate specificity of the acyltransferases implicated in their synthesis. These findings show higher diversity of grape and wine flavonols. Additional studies and isolation strategies need to be followed to further characterize these metabolites as to test their presence in other grape varieties and it wines.

Effect of the addition of mannoproteins on the interaction between wine flavonols and salivary proteins

It has been suggested that the addition of flavonols (i.e. white grape skins) improves and stabilizes the color of red wines. However, it has been shown that flavonol glycosides produce a mouth-drying and mouth-coating sensation at very low threshold concentrations. Moreover, the addition of polysaccharides to wines is a practice addressed to improve the smoothness and roundness and correct excessive astringency, so we have studied the effect of the addition of yeast mannoproteins (MP) on the interaction between quercetin 3-glucoside and human salivary peptides. Sensory analysis showed the first evidence of the mannoprotein smoothing effect when the flavonol is added to wine. Additionally, MP/SP/polyphenol interactions were studied using fluorescence spectroscopy, dynamic light scattering and isothermal titration calorimetry. Results obtained indicate not only the existence of interactions between mannoproteins and flavonols but also between mannoproteins and salivary proteins (SP), suggesting a possible formation of protein/polyphenol/polysaccharide ternary complex.

A sensitive microextraction by packed sorbent-based methodology combined with ultra-high pressure liquid chromatography as a powerful technique for analysis of biologically active flavonols in wines

A new approach based on microextraction by packed sorbent (MEPS) and reversed-phase high-throughput ultra high pressure liquid chromatography (UHPLC) method that uses a gradient elution and diode array detection to quantitate three biologically active flavonols in wines, myricetin, quercetin, and kaempferol, is described. In addition to performing routine experiments to establish the validity of the assay to internationally accepted criteria (selectivity, linearity, sensitivity, precision, accuracy), experiments are included to assess the effect of the important experimental parameters such as the type of sorbent material (C2, C8, C18, SIL, and C8/SCX), number of extraction cycles (extract-discard), elution volume, sample volume, and ethanol content, on the MEPS performance. The optimal conditions of MEPS extraction were obtained using C8 sorbent and small sample volumes (250μL) in five extraction cycle and in a short time period (about 5min for the entire sample preparation step). Under optimized conditions, excellent linearity (Rvalues2>0.9963), limits of detection of 0.006μgmL−1 (quercetin) to 0.013μgmL−1 (myricetin) and precision within 0.5–3.1% were observed for the target flavonols. The average recoveries of myricetin, quercetin and kaempferol for real samples were 83.0–97.7% with relative standard deviation (RSD, %) lower than 1.6%. The results obtained showed that the most abundant flavonol in the analyzed samples was myricetin (5.8±3.7μgmL−1). Quercetin (0.97±0.41μgmL−1) and kaempferol (0.66±0.24μgmL−1) were found in a lower concentration.The optimized MEPSC8 method was compared with a reverse-phase solid-phase extraction (SPE) procedure using as sorbent a macroporous copolymer made from a balanced ratio of two monomers, the lipophilic divinylbenzene and the hydrophilic N-vinylpyrrolidone (Oasis HLB) were used as reference. MEPSC8 approach offers an attractive alternative for analysis of flavonols in wines, providing a number of advantages including highest extraction efficiency (from 85.9±0.9% to 92.1±0.5%) in the shortest extraction time with low solvent consumption, fast sample throughput, more environmentally friendly and easy to perform.

Inhibition of colon adenocarcinoma cell proliferation by flavonols is linked to a G2/M cell cycle block and reduction in cyclin D1 expression

The moderate consumption of red wine has been proposed to reduce the incidence of colorectal cancer. Its anti-cancer action my in part be mediated by the actions of polyphenols on colon cancer epithelial cells. We show that a red wine phenolic (50μg/ml) extract devoid of anthocyanins (removed to reflect polyphenol bioavailability to the large intestine) and the major red wine flavonols quercetin, myricetin, laricitrin and syringetin (50μM) are capable of inhibiting the proliferation of colorectal epithelial adenocarcinoma cells. This anti-proliferative activity was partly mediated by the direct cytotoxic actions of flavonols and also their ability to cause a significant cell cycle blockage in G2/M. The anti-proliferative effects induced by flavonols were preceded, in most cases, by a strong and significant reduction of cyclooxygenase-2 (COX-2) and cyclin D1 expression. These results indicate that the observed inverse correlation between colon cancer and a moderate red wine intake may be partly mediated by the actions of red wine flavonols on the growth of cancer cells.

Distinct signalling mechanisms are involved in the dissimilar myocardial and coronary effects elicited by quercetin and myricetin, two red wine flavonols

Background and Aims Moderate red wine consumption associates with lower incidence of cardiovascular diseases. Attention to the source of this cardioprotection was focused on flavonoids, the non-alcoholic component of the red wine, whose intake inversely correlates with adverse cardiovascular events. We analysed whether two red wine flavonoids, quercetin and myricetin, affect mammalian basal myocardial and coronary function. Methods and results Quercetin and myricetin effects were evaluated on isolated and Langendorff perfused rat hearts under both basal conditions and α- and β-adrenergic stimulation. The intracellular signalling involved in the effects of these flavonoids was analysed on perfused hearts and by western blotting on cardiac and HUVEC extracts. Quercetin induced biphasic inotropic and lusitropic effects, positive at lower concentrations and negative at higher concentrations. Contrarily, Myricetin elicits coronary dilation, without affecting contractility and relaxation. Simultaneous administration of the two flavonoids only induced vasodilation. Quercetin-elicited positive inotropism and lusitropism depend on β1/β2-adrenergic receptors and associate with increased intracellular cAMP, while the negative inotropism and lusitropism observed at higher concentrations were α-adrenergic-dependent. NOS inhibition abolished Myricetin-elicited vasodilation, also inducing Akt, ERK1/2 and eNOS phosphorylation in both ventricles and HUVEC. Myricetin-dependent vasodilation increases intracellular cGMP and is abolished by triton X-100. Conclusions The cardiomodulation elicited on basal mechanical performance by quercetin and the selective vasodilation induced by myricetin point to these flavonoids as potent cardioactive principles, able to protect the heart in the presence of cardiovascular diseases.

Protective Effects of Red Wine Flavonols on 4‐Hydroxynonenal‐Induced Apoptosis in PC12 Cells

There is accumulating evidence that a moderate consumption of red wine has health benefits, such as the inhibition of neurodegenerative diseases. Although this is generally attributed to resveratrol, the protective mechanisms and the active substance(s) remain unclear. We examined whether and how red wine extract (RWE) and red wine flavonols quercetin and myricetin inhibited 4-hydroxynonenal (HNE)-induced apoptosis of rat pheochromocytoma PC12 cells. RWE attenuated HNE-induced PC12 cell death in a dose-dependent manner. HNE induced cleavage of poly(ADP-ribose) polymerase, which is involved in DNA repair in the nucleus, and this was inhibited by RWE treatment. Treatment with RWE also inhibited HNE-induced nuclear condensation in PC12 cells. Data of 2',7'-dichlorofluorescin diacetate showed that RWE protected against apoptosis of PC12 cells by attenuating intracellular reactive oxygen species. The cytoprotective effects on HNE-induced cell death were stronger for quercetin and myricetin than for resveratrol. HNE-induced nuclear condensation was attenuated by quercetin and myricetin. These results suggest that the neuroprotective potential of red wine is attributable to flavonols rather than to resveratrol.

Fast screening of total flavonols in wines, tea-infusions and tomato juice by flow injection/adsorptive stripping voltammetry

A novel approach for a fast screening of total flavonols (quercetin, kaempferol, myricetin) in wines, tea-infusions and tomato juice using adsorptive stripping voltammetry in a flow injection system is described. The proposed method is based on the property of flavonols to be pre-concentrated on carbon paste electrodes where diphenylether is used as the pasting liquid. The samples are subjected to an acid hydrolysis step and 1 mL sample of the diluted hydrolysate is injected in the flow injection apparatus. After 2 min pre-concentration period (under reciprocated flow) the electrode is washed with Britton–Robinson buffer, pH 5 solution and an anodic voltammetric scan is applied to produce an anodic current peak (analytical signal). The lower determination limits for kaempferol, quercetin and myricetin in pure aqueous solutions were 20, 9 and 25 μg L −1. Mixtures of flavonols resulted into a single anodic peak, which can be used for the calculation of the total flavonols concentration expressed in terms of “quercetin equivalent”. The measurement throughput was about 13 h −1 and the overall reproducibility of measurements was 3–6%. The total concentration of quercetin equivalent in eight tested samples was found in the range 3–60 mg L −1 and the results compare favorably with those obtained by an LC procedure.