New flavanol O-glycosides in grape and wine.

The presence of monomeric and dimeric flavan-3-ol monohexosides was investigated in grapes and wines. Polyphenol extracts were prepared from grape seeds and skins (Syrah, Merlot, and Cabernet-Sauvignon) sampled at three different developmental stages. Different wines (Tannat, Alicante, Syrah, Merlot, and Grenache) were also studied.

p-Hydroxyphenyl-pyranoanthocyanins: An Experimental and Theoretical Investigation of Their Acid-Base Properties and Molecular Interactions.

The physicochemical properties of the wine pigments catechyl-pyranomalvidin-3--glucoside (PA1) and guaiacyl-pyranomalvidin-3--glucoside (PA2) are extensively revisited using ultraviolet (UV)-visible spectroscopy, dynamic light scattering (DLS) and quantum chemistry density functional theory (DFT) calculations. In mildly acidic aqueous solution, each cationic pigment undergoes regioselective deprotonation to form a single neutral quinonoid base and water addition appears negligible. Above pH = 4, both PA1 and PA2 become prone to aggregation, which is manifested by the slow build-up of broad absorption bands at longer wavelengths (λ ≥ 600 nm), followed in the case of PA2 by precipitation.

Synthesis, Identification, and Structure Elucidation of Adducts Formed by Reactions of Hydroxycinnamic Acids with Glutathione or Cysteinylglycine.

Grape polyphenols, especially hydroxycinnamic acids such as caftaric and caffeic acid, are prone to enzymatic oxidation reactions during the winemaking process, forming o-quinones and leading to color darkening. Glutathione is capable of trapping these o-quinones and thus limiting juice browning. In this study, the addition of glutathione or cysteinylglycine onto caftaric or caffeic acid o-quinones formed by polyphenoloxidase-catalyzed reactions was investigated by UPLC-DAD-ESIMS and NMR data analyses.

How to gain insight into the polydispersity of tannins: a combined MS and LC study.

In the context of the potential health benefits of food polyphenols, the bioavailability of tannins (i.e. proanthocyanidins) is a major issue, which is strongly influenced by the polydispersity and the degree of polymerisation of tannins.

Qualitative and semi-quantitative analysis of phenolics in Eucalyptus globulus leaves by high-performance liquid chromatography coupled with diode array detection and electrospray ionisation mass spectrometry.

Introduction: Eucalyptus species are widely cultivated in Mediterranean regions. Moreover, plants of this family have been utilized for medicinal purposes. A number of studies have been devoted to the identification of eucalypt phenolics, all of them have focused on specific families of compounds, and no exhaustive profiling has been reported in leaves of this plant.

Comprehensive study of condensed tannins by ESI mass spectrometry: average degree of polymerisation and polymer distribution determination from mass spectra.

The determination of the molecular mass distribution of tannins is still a challenge. To elucidate it, mass spectrometry is potentially interesting, but many previous studies have highlighted that the mass spectra of a tannin fraction do not always reflect the actual abundance of different chain lengths. To clarify the potentialities offered by the MS approach, a comprehensive study involving different tannin fractions analysed under different conditions was conducted with an electrospray ionization (ESI) source.

Analysis by high-performance liquid chromatography diode array detection mass spectrometry of phenolic compounds in fruit of Eucalyptus globulus cultivated in Algeria.

A method based on high-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS) following fractionation by chromatography on a Sephadex LH-20 column has been developed to determine the phenolic composition of fruit of Eucalyptus globulus growing in Algeria. The presence of 18 gallotannins, 26 ellagitannins, and 2 flavonols was established. Tentative identification is provided for these compounds on the basis of UV-visible spectra and mass spectrometry data.

Grapevine MATE-type proteins act as vacuolar H+-dependent acylated anthocyanin transporters.

In grapevine (Vitis vinifera), anthocyanins are responsible for most of the red, blue, and purple pigmentation found in the skin of berries. In cells, anthocyanins are synthesized in the cytoplasm and accumulated into the vacuole. However, little is known about the transport of these compounds through the tonoplast.

Direct mass spectrometry approaches to characterize polyphenol composition of complex samples.

Lower molecular weight polyphenols including proanthocyanidin oligomers can be analyzed after HPLC separation on either reversed-phase or normal phase columns. However, these techniques are time consuming and can have poor resolution as polymer chain length and structural diversity increase. The detection of higher molecular weight compounds, as well as the determination of molecular weight distributions, remain major challenges in polyphenol analysis.

Interactions between yeast lees and wine polyphenols during simulation of wine aging. II. Analysis of desorbed polyphenol compounds from yeast lees.

In the first part of this work, the analysis of the polyphenolic compounds remaining in the wine after different contact times with yeast lees during simulation of red wine aging was undertaken. To achieve a more precise view of the wine polyphenols adsorbed on lees during red wine aging and to establish a clear balance between adsorbed and remnant polyphenol compounds, the specific analysis of the chemical composition of the adsorbed polyphenolic compounds (condensed tannins and anthocyanins) after their partial desorbtion from yeast lees by denaturation treatments was realized in the second part of the study. The total recovery of polyphenol compounds from yeast lees was not complete, since a rather important part of the initial wine colored polyphenols, especially those with a dominant blue color component, remained strongly adsorbed on yeast lees, as monitored by color tristimulus and reflectance spectra measurements.

Interactions between yeast lees and wine polyphenols during simulation of wine aging: I. Analysis of remnant polyphenolic compounds in the resulting wines.

Wine aging on yeast lees is a traditional enological practice used during the manufacture of wines. This technique has increased in popularity in recent years for the aging of red wines. Although wine polyphenols interact with yeast lees to a limited extent, such interactions have a large effect on the reactivity toward oxygen of wine polyphenolic compounds and yeast lees.