New Light on the Varietal Thiols Pathway during Alcoholic Fermentation: Role of 3--(-Acetyl-cysteinyl)-hexan-1-ol (NAC3SH).

For many years, knowledge on thiol precursors has been limited to -conjugates of glutathione (G3SH), cysteine (Cys3SH), and later on the dipeptides γ-GluCys and CysGly. In this work, we took the parallel between precursor degradation and the glutathione-mediated detoxification pathway a step further by considering a new type of derivative, 3--(-acetyl-l-cysteinyl)hexanol (NAC3SH). This compound was synthesized and then added to the existing liquid chromatography with tandem mass spectrometry (LC-MS/MS) method of thiol precursors.

First identification of a new molecule involved in the fresh mushroom off-flavor in wines: 1-hydroxyoctan-3-one.

The fresh mushrooms off-flavor (FMOff) has been appearing in wines since the 2000 s; the C8 compounds, 1-octen-3-one, 1-octen-3-ol and 3-octanol are involved in this specific taint, yet they alone do not fully explain its occurrence. The objective of this work was to identify by GC-MS new FMOff markers in contaminated matrices, to correlate compound levels with wine sensory characterization and to determine the sensory attributes of 1-hydroxyoctan-3-one, a new candidate involved in FMOff. In practice, grape musts were artificially contaminated with Crustomyces subabruptus, and fermented to obtain tainted wines.

Unambiguous NMR Structural Determination of (+)-Catechin-Laccase Dimeric Reaction Products as Potential Markers of Grape and Wine Oxidation.

(+)-Catechin-laccase oxidation dimeric standards were hemi-synthesized using laccase from in a water-ethanol solution at pH 3.6. Eight fractions corresponding to eight potential oxidation dimeric products were detected.

Multimethod Approach for Extensive Characterization of Gallnut Tannin Extracts.

Gallotannins extracted from gallnuts are commonly added to wine to improve its properties. They consist of mixtures of galloylester derivatives of glucose. However, their composition and properties are not well-established.

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.

and P-NMR Study of the Phosphate Transport and Polyphosphate Metabolism in in Response to Plant Roots Signals.

We used and phosphorus-31 nuclear magnetic resonance (P-NMR) spectroscopy to follow the change in transport, compartmentation and metabolism of phosphate in the ectomycorrhizal fungus in response to root signals originating from host () or non-host () plants. A device was developed for the studies allowing the circulation of a continuously oxygenated mineral solution in an NMR tube containing the mycelia. The studies were performed on fungal material after several consecutive treatment steps (freezing in liquid nitrogen; crushing with perchloric acid; elimination of perchloric acid; freeze-drying; dissolution in an appropriate liquid medium).

Quantification of hydroxycinnamic derivatives in wines by UHPLC-MRM-MS.

A UHPLC-MS/MS method was developed for the quantification of the main compounds involved in oxidation reactions occurring in white musts and wines such as hydroxycinnamic acids, their glutathione and cysteinylglycine adducts (GRP, GRP2, 5-(S-glutathionyl)-trans-caftaric acid, 2-(S-cysteinylglycyl)-trans-caftaric acid, and 2-(S-glutathionyl)-trans-caffeic acid), and reduced and oxidized glutathione (GSH, GSSG) in wine. Since oxidation is the main concern in white wine-making, directly affecting its quality, the developed method was then applied in a series of white wines made with different pre-fermentation treatments to limit oxidation at must stage. The glucose esters and/or glucosides of hydroxycinnamic acids were quantified as glucogallin equivalent.

Establishing a Symbiotic Interface between Cultured Ectomycorrhizal Fungi and Plants to Follow Fungal Phosphate Metabolism.

In ectomycorrhizal plants, the fungal cells colonize the roots of their host plant to create new organs called ectomycorrhizae. In these new organs, the fungal cells colonize the walls of the cortical cells, bathing in the same apoplasm as the plant cells in a space named the 'Hartig net', where exchanges between the two partners take place. Finally, the efficiency of ectomycorrhizal fungi to improve the phosphorus nutrition of their host plants will depend on the regulation of phosphate transfer from the fungal cells to plant cells in the Hartig net through as yet unknown mechanisms.

A Method for Radioactive Labelling of to Study Plant-fungus Interactions.

In order to quantify P accumulation and P efflux in the ectomycorrhizal basidiomycete fungus , we supplied P to mycelia previously grown in liquid medium. The culture had four main steps that are 1) growing the mycelium on complete medium with P, 2) transfer the mycelia into new culture solution with or without P, 3) adding a solution containing P and 4) rinsing the mycelia before incubation with or without plant. The main point is to rinse very carefully the mycelia after P supply in order to avoid overestimation of P efflux into the medium.

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.

The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and P NMR spectroscopy study.

Ectomycorrhizal (ECM) association can improve plant phosphorus (P) nutrition. Polyphosphates (polyP) synthesized in distant fungal cells after P uptake may contribute to P supply from the fungus to the host plant if they are hydrolyzed to phosphate in ECM roots then transferred to the host plant when required. In this study, we addressed this hypothesis for the ECM fungus Hebeloma cylindrosporum grown in vitro and incubated without plant or with host (Pinus pinaster) and non-host (Zea mays) plants, using an experimental system simulating the symbiotic interface.

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.

A comprehensive investigation of guaiacyl-pyranoanthocyanin synthesis by one-/two-dimensional NMR and UPLC-DAD-ESI-MS(n).

In red and rosé wines, the grape anthocyanins are progressively converted to more stable pigments, including phenylpyranoanthocyanins. One-/two-dimensional NMR and UPLC-DAD-ESI-MS(n) measurements were used to monitor the synthesis of guaiacylpyranomalvidin 3-O-glucoside from malvidin 3-O-glucoside and vinylguaiacol in model solutions and identify the products formed during the reaction. The highest conversion rates (30%, determined by (1)H qNMR) were obtained with a small excess of vinylguaiacol in methanol/water (70/30) at pH 3 and 35°C.

Straightforward synthesis of deuterated precursors to demonstrate the biogenesis of aromatic thiols in wine.

Straightforward synthesis of labeled S-3-(hexan-1-ol)-glutathione and S-4-(4-methylpentan-2-one)-glutathione has been developed through a conjugate addition optimization study. Sauvignon blanc fermentation experiments with the [(2)H(10)] S-4-(4-methylpentan-2-one)-glutathione used as a tracer released the corresponding deuterated thiol, thus proving the direct relationship with the 4-mercapto-4-methylpentan-2-one under enological conditions. The conversion yield of such transformation was estimated to be close to 0.

Synthesis of modified proanthocyanidins: easy and general introduction of a hydroxy group at C-6 of catechin; efficient synthesis of elephantorrhizol.

A general procedure for the oxidation of catechin derivatives is described, leading to the introduction of a new hydroxy group at C-6. This procedure has been applied for the synthesis of elephantorrhizol, a natural flavan-3-ol exhibiting a fully substituted cycle A.

Synthesis of modified proanthocyanidins: introduction of acyl substituents at C-8 of catechin. Selective synthesis of a C-4-->O-->C-3 ether-linked procyanidin-like dimer.

The regioselective introduction of substituents at C-8 of (+)-catechin is described, leading to the synthesis of several catechin derivatives with various substitution patterns to be used for the further synthesis of modified proanthocyanidins. Thereafter, a new 3-O-4 ether-linked procyanidin-like derivative was synthesized. Its formation was selectively achieved through TiCl(4)-catalyzed condensation of 4-(2-hydroxyethoxy)tetra-O-benzyl catechin with the 8-trifluoroacetyl adduct of tetra-O-benzyl catechin.

Characterization of a colorless anthocyanin-flavan-3-ol dimer containing both carbon-carbon and ether interflavanoid linkages by NMR and mass spectrometry.

Direct addition of anthocyanins and flavan-3-ols was investigated in a model system by incubating malvidin 3-glucoside and (-)-epicatechin in ethanol. Analysis of reaction products by high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC/ESI-MS) before and after thiolysis showed the formation of colorless dimers detected at m/z 781 in the negative ion mode, with retention times and spectroscopic characteristics identical to those of compounds detected in wine, which contain one malvidin 3-glucoside unit and one flavanol unit. On the basis of their resistance to thiolysis, these compounds were postulated to be bicyclic dimers linked with both carbon-carbon and ether bonds as observed in the case of A type proanthocyanidins.