Yves Glories

Characterisation of oligomeric and polymeric procyanidins from grape seeds by liquid secondary ion mass spectrometry

Abstract Several fractions of oligomeric and polymeric procyanidins have been obtained from grape seeds by gel chromatography on Fractogel TSK. Their molecular weights (Mw) were directly determined by Liquid Secondary Ion Mass Spectrometry (LSIMS). We observed that tannins were molecules with a wide range of Mw: from 290 to 3100 (decamers). Catechins (Mw 290), procyanidin dimers (Mw 578), (−)-epicatechin gallate (Mw 442), procyanidin dimer gallates (Mw 730), procyanidin dimer digallates (Mw 882), procyanidin trimers (Mw 866) and procyanidin trimer gallates (Mw 1018), were identified as (M−H) − quasimolecular ions by negative LSIMS. Some structures were elucidated by partial thiolysis and enzymatic hydrolysis.

Concentration and compositional changes of procyanidins in grape seeds and skin of white Vitis vinífera varieties

Grapes from Semillon and Ugni blanc varieties have been sampled over the periods just before coloration (stage I), veraison (stage II) and harvest (stage III), during the seasons 1991–92 and 1992–93. The content of total extractable proanthocyanidins, catechins ((+)-catechin, (−)-epicatechin and (−)-epicatechin gallate), procyanidin dimers B1 to B8 and trimer C1 in skin and grape seeds were further determined. The quantitative determination was performed through Fractogel TSK chromatography followed by HPLC analysis. The highest concentration of procyanidins is present in the grapes in the early stages of development. (+)-Catechin was the major constituent of flavan-3-ols in skin and grape seeds. Procyanidin dimers B1, B4 and B6 represent the majority of dimers in the early stage of grape seeds development, while in the last stage of maturation dimers B2 and B4 were predominant. Curiously, the decrease in the procyanidins concentration goes along with a corresponding increase of dimer B2 synthesis during grape ripening. Dimer B1 was always the major dimer in skin. The differences between the two seasons were more significant than those between the Ugniblanc and Semillon varieties. However, Semillon contains a higher concentration of total proanthocyanidins. © 1999 Society of Chemical Industry

Free radical scavenging effect of anthocyanins in red wines

Free radicals are extremely harmful to living organisms in that, they attack different constituents of the cell, leading to acceleration of the ageing process and sometimes even its destruction, or if the DNA is affected, irreversible malfunctions. It is now widely recognised that the phenolic compounds of wine have very high free radical scavenging potential. The aim of this paper is to determine which of these phenolic compounds are responsible for the strong free radical scavenging potential of red wines. In order to do so, a red wine was fractionated into phenolic fractions. After extraction and purification of these compounds from the wine, we have measured their free radical scavenging activities using an enzymatic method. The anthocyanic fraction showed a high free radical scavenging power in relation to the other tannic fractions. In order to explain this phenomenon, some pure anthocyanins were studied and a relationship between their free radical scavenging activity and their molecular structure was suggested.

(+)-Catechin—acetaldehyde condensation products in relation to wine-ageing

Abstract Dimers resulting from acetaldehyde-flavanol condensation were studied in an acidic hydroalcoholic medium (12% ethanol pH 3.2) in order to simulate the conditions of wine tannin-transformation during the wine-ageing process. One of the dimers was isolated after hemisynthesis and studied by mass spectrometry, NMR and molecular mechanics. Mass spectrometric analysis was in accordance with a dimeric structure with a CH-CH 3 linkage. NMR showed the presence of a 6–8 (ethane-1,1-diyl)di(+)-catechin. The carbon atoms, C-6 and C-8, involved in the linkage, have, an asymmetric conformation, with the two catechols in an equatorial position.

Determination of the Composition of Commercial Tannin Extracts by Liquid Secondary Ion Mass Spectrometry (LSIMS)

The composition of various commercial tannin extracts were determined by liquid secondary ion mass spectrometry (LSIMS). Spectra were obtained directly from tannin extracts without any pre-separation. Eight different tannin powders were analysed : three gallotannins (Chinese, Turkish, tara), three ellagitannins (sweet chestnut, pendunculata oak, sessile oak), one mixed hydrolysable tannin (myrabolans) and one proanthocyanidin (grape seeds). This method enabled the main molecules in these powders to be identified.

Structure simulation of two ellagitannins from Quercus robur L.

Abstract Two major ellagitannins from Quercus robur , vescalagin and castalagin, were studied by 1 HNMR and LSI-mass spectrometry, and molecular mechanics. A plausible 3D-structure is proposed for each of the two diastereoisomers. These structures were the most stable ones found after a conformational analysis study and their calculated NMR spectra are in good accordance with measured ones.

A complete structural and conformational investigation of procyanidin A2 dimer

Abstract Structural and conformational study of A2 procyanidin is presented. By using NMR and molecular mechanics. A demonstration of the C4–C8 bond and of an additional C2-O-C7 ether linkage, characteristics of the procyanidin of A-series, was achieved.

A biochemical approach to the evolution of procyanidins in grape seeds during the ripening of red

Seed extracts of one clone of Merlot Noir were studied during maturation using low‐pressure and high‐performance liquid chromatography to observe changes in composition and to follow the evolution of the main procyanidins. These observations have prompted our laboratory to investigate the polymerisation of procyanidins associated with their extraction with an alcoholic solvent. We report the observed correlations for procyanidin dimers, which are relatively high between procyanidins B2/C1/A2 themselves (linked by C4—C8 bond), but which are non‐existent between procyanidins linked by C4—C8 and by C4—C6 bonds. These observations have enabled us to propose a hypothesis regarding procyanidin oligomer biosynthesis.

High Performance Thin Layer Chromatography (HPTLC) Analysis of Red Wine Pigments

An HPTLC method has been developed to give qualitative and quantitative information on red wine pigments. The samples are prepared by solid-phase extraction (SPE) on C18 cartridges. Analytical determination is done by chromatography on C18 silica gel plates with isocratic elution with methanol—water—trifluoracetic acid, 55 + 45 + 1 (v/v). This method leads to the clear separation of the three classes of Vitis vinifera anthocyanins with good statistical repeatability and reproducibility for wines of different vintages. It also enables evaluation of the amount of polymeric pigments in red wines.

Isolation of berry skin protoplasts and improvement of their produce

It is known that the phenolic compounds and particularly procyanidins, which are found in relatively large quantities in the skin, have a high affinity against proteins and therefore are capable of inhibiting some enzyme activities. This work proposes a study of the isolation of the Cabernet franc skin protoplasts and a try to improve their performance by determining the influence of some factors.