Christiane Vitry

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.

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.

Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine – Possible Contribution of These Products to Colour

This paper describes the formation and diversity of new compounds resulting from the polymerisation of furanic and phenolic flavanol-aldehydes with HPLC‑DAD and LC‑ES/MS analysis. Polymerisation, resulting from nucleophilic reactions, formed dimers, trimers, soluble and insoluble polymers. Reactions in hydroalcoholic solution with pure aldehydes (phenolic and furanic) and flavanols (catechin) were studied. The study was repeated with different aldehydes in white wine. This research focused particularly on the colour properties of the released products and their potential impact on the colour of white wine. Some products were purified and isolated; these were mainly catechinfurfuraldehyde, catechin-methyl-5-furfuraldehyde, catechin-hydroxymethyl-furfuraldehyde, catechin-vanillin, and catechin-syringaldehyde dimers. The most powerful coloured products resulted from furanic aldehydes. Over the course of the experiment, the reaction produced dimers, trimers and oligomers. After 50 to 60 days, the colour of the solution was mainly due to soluble polymeric forms. In addition, the role of SO2, generally used during vinification and ageing, was studied. The influence of SO2 on the kinetics of the reaction was limited.

Unexpected matrix interactions in liquid secondary ion mass spectrometry of two pyranosyl mercaptans

An unexpected interaction with a thioglycerol matrix appeared in the liquid secondary ion mass spectrometry (LSIMS) spectra of two pyranosyl mercaptans [2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranose (1a) and 2,3,4,6-tetra-O-acetyl-1,5-dithio-β-D-glucopyranose (1b)] often used to prepare glucosinolates, important thiosaccharidic metabolites found in all plants of the order Brassicales. The reactions, probably occurring in the solvent cage, seem to involve radical mechanisms.