Jean-Claude Delaunay

Preparative isolation of polyphenolic compounds from Vitis vinifera by centrifugal partition chromatography

This study deals with a centrifugal partition chromatography developed for the separation of phenolic compounds from Vitis vinifera. EtOAc grape seed extracts were separated using the solvent system hexane-ethyl acetate-ethanol-water (1:8:2:7; v/v) in two fractions: one containing about 75% of flavanol monomers (catechin and epicatechin) corresponding to 18% of crude extract and another fraction B-type dimers (22% of crude extract). From the stalk extracts, we could separate stilbenoid compounds (resveratrol and its oligomers; 12% of crude extract) which were eluted in less than 30 min from flavanols (which required a few hours of additional elution). Using the same solvent system but in different ratios (4:5:3:3; v/v), we isolated the trans-resveratrol (7@1000; 90% purity).

Anthocyanin identification and composition of wild Vitis spp. accessions by using LC–MS and LC–NMR

The composition and concentration of anthocyanins of grape berry skins were analyzed in order to assess phenotypic variation between four grape wine varieties belonging to 4 different species: Vitis vinifera, Vitis amurensis, Vitis cinerea and Vitis X champinii. High-performance liquid chromatography coupled to mass spectrometry (LC-MS) and NMR spectroscopy (LC-NMR) were used to separate and identify the structure of anthocyanins present in these species. Combination of LC-MS and LC-NMR data resulted in the identification of 33 anthocyanins. In particular, newly reported cis isomers of p-coumaric-derivatives were identified (petunidin-, peonidin- and malvidin-3-(6-p-coumaroyl)-5-diglucoside). In V. cinerea and V. vinifera, anthocyanins were monoglucoside derivatives whereas in V. amurensis and V. X champinii, both mono- and diglucoside derivatives were identified. Malvidin-, delphinidin- and petunidin-derivatives were, respectively, the most abundant components in V. cinerea and V. vinifera, V. amurensis and V. X champinii.

New stilbene dimers against amyloid fibril formation.

Twenty stilbene derivatives and moracin M extracted from natural products were tested against amyloid-beta peptide (Abeta) aggregation. Results of stilbene monomer derivatives indicated that interaction with resveratrol and piceid was specific. Concerning oligomers, scirpusin A and epsilon-viniferin glucoside demonstrated a strong inhibition of the aggregation process.

The polyphenol piceid destabilizes preformed amyloid fibrils and oligomers in vitro: hypothesis on possible molecular mechanisms.

Alzheimer’s disease (AD) is characterized by deposits of amyloid in various tissues. The neuronal cytotoxicity of Aβ peptides is attributed not only to various mechanisms but also to amyloid fibrils and soluble oligomeric intermediates. Consequently, finding molecules to prevent or reverse the oligomerization and fibrillization of Aβ could be of therapeutic value in the treatment of AD. We show that piceid, a polyphenol of the stilbene family, destabilized fibrils and oligomers to give back monomers that are not neurotoxic molecules. The mechanism of this destabilization could be a dynamic interaction between the polyphenol and the Aβ that could open the hydrophobic zipper and shift the reversible equilibrium “random coil⇔β-sheet” to the disordered structure.

Preparative purification of antiamyloidogenic stilbenoids from Vitis vinifera (Chardonnay) stems by centrifugal partition chromatography

Five stilbenoids, E-resveratrol, E-piceatannol, (+) E-(epsilon)-viniferin, (+)-ampelopsin A and vitisin C were isolated from methyl tert-butyl ether (MtBE) stem extract of Vitis vinifera (Chardonnay cv). Their purification on a preparative scale was obtained by centrifugal partition chromatography (CPC) using quaternary Arizona solvent systems composed of n-heptane/ethyl acetate/methanol/water. We tested 23 Arizona solvent systems to partition the extract and found that systems K and M (Hept/EtOAc/MeOH/water, 1:2:1:2 and 5:6:5:6, respectively; v/v) were the best to separate the stilbenes mentioned above. This support-free liquid-liquid chromatographic procedure made it possible to isolate ampelopsin A from V. vinifera for the first time. The antiamyloidogenic activity of the isolated stilbenes was evaluated versus beta-amyloid fibrils. E-resveratrol and (+)-ampelopsin A were found to be the most active compounds with 63 and 46% inhibition at 10microM, respectively. These findings suggest that E-resveratrol and (+)-ampelopsin A may function as attractive new candidates for protecting against brain cell dysfunction in vivo in AD by inhibiting the aggregation of Abeta.

Flavonol profiles in berries of wild Vitis accessions using liquid chromatography coupled to mass spectrometry and nuclear magnetic resonance spectrometry

The flavonol profiles of grape berry skins were analysed in order to assess phenotypic variation between six grapevines belonging to six different species: Vitis vinifera, Vitiscandicans, Vitischampinii, Vitisamurensis, Vitiscinerea and Vitisdoaniana. High-performance liquid chromatography coupled to mass spectrometry (LC-MS) and NMR spectrometry (LC-NMR) were used to separate and identify the flavonols present in these species. The combination of LC-MS and LC-NMR data resulted in the identification of eighteen flavonols. In particular, the new flavonol diglycoside and pentoside derivatives were determined. In addition, the antioxidant capacities of flavonol grape skin extracts were evaluated by using an oxygen radical absorbance capacity method (ORAC).

Anthocyanin Phytochemical Profiles and Anti‐oxidant Activities of Vitis candicans and Vitis doaniana

INTRODUCTION Grapes are one of the most important fruit crops in the world. The quality of red grape berries greatly depends on skin colour, mainly due to the anthocyanin profile. Today, the American Vitis species have the greatest potential for breeding work. They have multiple resistance properties in comparison with Vitis vinifera but little is known about their anthocyanin content. OBJECTIVE To determine the anti-oxidant properties and anthocyanin profile of two American species, Vitis candicans and Vitis doaniana, by using LC-MS(n) and LC-NMR. METHODS Grape extracts were prepared by extraction of berry skins with acidified methanol. The complete structure elucidation of the individual anthocyanins was performed with LC-MS(n) , LC-NMR and NMR experiments. Individual anthocyanins in the extracts were quantified by using malvidin glucoside as external standard. The anti-oxidant activities of grape skin extracts were evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH•) radical scavenging and oxygen radical absorbance capacity (ORAC) assays. RESULTS By using LC-MS(n) and LC-NMR experiments, 30 anthocyanins were identified and quantified in the two Vitis species, including two new cis-p-coumaroyl derivatives. Vitis candicans and V. doaniana showed significant differences in their anthocyanin profile. These two Vitis species possess low-to-medium anti-oxidant activities in comparison with V. vinifera. CONCLUSION The profiles of 30 anthocyanins were established unambiguously in two American Vitis species.

Polyphenols from the stems of Morus alba and their inhibitory activity against nitric oxide production by lipopolysaccharide-activated microglia

Neuroinflammatory processes are involved in the pathogenesis of many neurodegenerative disorders. Microglial cells, the main immune cells of the central nervous system, represent a target of interest to search for naturally occurring anti-inflammatory products. In this study, we evaluated the anti-inflammatory properties of polyphenols obtained from the stems of Morus alba. This edible species, known as white mulberry, is frequently studied because of its traditional use in Asian medicine and its richness in different types of polyphenols, some of which are known to be phytoalexins. One new coumarin glycoside, isoscopoletin 6-(6-O-β-apiofuranosyl-β-glucopyranoside) (1) was mainly isolated by CPC (centrifugal partition chromatography) from this plant, together with seven known polyphenols (2-8). Their structures were established on the basis of spectroscopic analyses including extensive 2D NMR studies. The eight isolated compounds were evaluated for their inhibitory activities on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 microglial cells. The absence of cell toxicity is checked by a MTT assay.

Bioactive stilbenes from Vitis vinifera grapevine shoots extracts

BACKGROUND Viticultural residues from commercial viticultural activities represent a potentially important source of bioactive stilbenes such as resveratrol. The main aim of the present study was therefore to isolate, identify and perform biological assays against amyloid-β peptide aggregation of original stilbenes from Vitis vinifera shoots. RESULTS A new resveratrol oligomer, (Z)-cis-miyabenol C (3), was isolated from Vitis vinifera grapevine shoots together with two newly reported oligostilbenes from Vitis vinifera shoots, vitisinol C (1) and (E)-cis-miyabenol C (2), and six known compounds: piceatannol, resveratrol, (E)-ε-viniferin (trans-ε-viniferin), ω-viniferin, vitisinol C and (E)-miyabenol C. The structures of these resveratrol derivatives were established on the basis of detailed spectroscopic analysis including nuclear magnetic resonance experiments. All the newly reported compounds were tested for their anti-aggregative activity against amyloid-β fibril formation. Vitisinol C was found to exert a significant activity against amyloid-β aggregation. CONCLUSION Vitis vinifera grapevine shoots are potentially interesting as a source of new bioactive stilbenes, such as vitisinol C.

Unusual compounds from Galium mollugo and their inhibitory activities against ROS generation in human fibroblasts.

Three unusual dioxatricyclodecenone compounds, mollugoside A, E-mollugoside B and Z-mollugoside B and, together with known flavonoids, were isolated from the aerial parts of Galium mollugo collected in north-eastern Algeria. Their structures were elucidated by analysis of spectroscopic data, including 1D and 2D NMR. Flavonoids and mollugoside A significantly reduced reactive oxygen species (ROS) generation in human fibroblasts.