Viniphenol A, a complex resveratrol hexamer from Vitis vinifera stalks: structural elucidation and protective effects against amyloid-ß-induced toxicity in PC12 cells.

Stilbenes have received much attention during the last two decades following the discovery of resveratrol in wine. Since then, there have been a growing number of papers reporting various biological activities of naturally occurring stilbenes. The aim of this study was to determine new minor stilbenes from Vitis vinifera stalks. Purification of these compounds was achieved by means of centrifugal partition chromatography, a versatile separation technique that does not require a solid stationary phase. Viniphenol A (1), a new resveratrol hexamer, was isolated along with five oligostilbenoids identified in V. vinifera for the first time, ampelopsin C, davidiol A, leachianol F, leachianol G, and E-maackin, a dimer with an unusual dioxane moiety, and 14 known hydroxystilbenes. The structure and stereochemistry of viniphenol A were determined on the basis of spectroscopic data analysis and molecular modeling under NMR constraints. Viniphenol A showed protective effects against amyloid-ß-induced toxicity in PC12 cell cultures.

Natural stilbenoids isolated from grapevine exhibiting inhibitory effects against HIV-1 integrase and eukaryote MOS1 transposase in vitro activities.

Polynucleotidyl transferases are enzymes involved in several DNA mobility mechanisms in prokaryotes and eukaryotes. Some of them such as retroviral integrases are crucial for pathogenous processes and are therefore good candidates for therapeutic approaches. To identify new therapeutic compounds and new tools for investigating the common functional features of these proteins, we addressed the inhibition properties of natural stilbenoids deriving from resveratrol on two models: the HIV-1 integrase and the eukaryote MOS-1 transposase. Two resveratrol dimers, leachianol F and G, were isolated for the first time in Vitis along with fourteen known stilbenoids: E-resveratrol, E-piceid, E-pterostilbene, E-piceatannol, (+)-E-ε-viniferin, E-ε-viniferinglucoside, E-scirpusin A, quadragularin A, ampelopsin A, pallidol, E-miyabenol C, E-vitisin B, hopeaphenol, and isohopeaphenol and were purified from stalks of Vitis vinifera (Vitaceae), and moracin M from stem bark of Milliciaexelsa (Moraceae). These compounds were tested in in vitro and in vivo assays reproducing the activity of both enzymes. Several molecules presented significant inhibition on both systems. Some of the molecules were found to be active against both proteins while others were specific for one of the two models. Comparison of the differential effects of the molecules suggested that the compounds could target specific intermediate nucleocomplexes of the reactions. Additionally E-pterostilbene was found active on the early lentiviral replication steps in lentiviruses transduced cells. Consequently, in addition to representing new original lead compounds for further modelling of new active agents against HIV-1 integrase, these molecules could be good tools for identifying such reaction intermediates in DNA mobility processes.

3D NMR structure of a complex between the amyloid beta peptide (1-40) and the polyphenol ε-viniferin glucoside: implications in Alzheimer's disease.

BACKGROUND: Alzheimer's disease (AD) is a progressive neurodegenerative disorder. There is a consensus that Aß is a pathologic agent and that its toxic effects, which are at present incompletely understood, may occur through several potential mechanisms. Polyphenols are known to have wide-ranging properties with regard to health and for helping to prevent various diseases like neurodegenerative disorders. Thus inhibiting the formation of toxic Aß assemblies is a reasonable hypothesis to prevent and perhaps treat AD METHODS: Solution NMR and molecular modeling were used to obtain more information about the interaction between the Aß1-40 and the polyphenol ε-viniferin glucoside (EVG) and particularly the Aß residues involved in the complex. RESULTS: The study demonstrates the formation of a complex between two EVG molecules and Aß1-40 in peptide characteristic regions that could be in agreement with the inhibition of aggregation. Indeed, in previous studies, we reported that EVG strongly inhibited in vitro the fibril formation of the full length peptides Aß1-40 and Aß1-42, and had a strong protective effect against PC12 cell death induced by these peptides. CONCLUSION: For the full length peptide Aß1-40, the binding sites observed could explain the EVG inhibitory effect on fibrillization and thus prevent amyloidogenic neurotoxicity. GENERAL SIGNIFICANCE: Even though this interaction might be important at the biological level to explain the protective effect of polyphenols in neurodegenerative diseases, caution is required when extrapolating this in vitro model to human physiology.

Inhibitory activity of plant stilbenoids against nitric oxide production by lipopolysaccharide-activated microglia.

Microglia-driven inflammatory processes are thought to play an important role in ageing and several neurological disorders. Since consumption of a diet rich in polyphenols has been associated with anti-inflammatory and neuroprotective effects, we studied the effects of twenty-five stilbenoids isolated from Milicia excelsa, Morus alba, Gnetum africanum, and Vitis vinifera. These compounds were tested at 5 and 10 µM on BV-2 microglial cells stimulated with bacterial lipopolysaccharide. Ten stilbenoids reduced lipopolysaccharide-induced nitric oxide production at 5 and/or 10 µM. Two tetramers, E-vitisin A and E-vitisin B, were the most effective molecules. Moreover, they attenuated the expression of the inducible NO synthase protein and gene.

Chemical dereplication of wine stilbenoids using high performance liquid chromatography-nuclear magnetic resonance spectroscopy.

Wine is a major dietary source of numerous potentially health promoting stilbenoids that have been the subject of many qualitative and quantitative studies. However, our initial HPLC-MS analyses of crude wine samples demonstrated the presence of compounds with molecular weights matching characteristic stilbenoid dimers, trimers, and tetramers that were unaccounted for in the literature. Due to the likelihood that these are known compounds, a chemical dereplication method is highly desirable. We developed such a method using LC-DAD-MS monitored fractionation steps, using adsorption and centrifugal partition chromatography (CPC), to obtain fractions rich in stilbenoids for analysis in stopped-flow LC-NMR. (1)H NMR spectra and MS data were cross-referenced with our laboratory database and the literature for identification. This method yielded highly useful structural information, allowing the characterization of previously unidentified stilbenoids in wine, ampelopsin C, isohopeaphenol, quadrangularin A, and E-ω-viniferin. These results demonstrate the usefulness of stop-flow LC-NMR in conjunction with LC-MS guided fractionation for the dereplication of compounds of interest in general, and specifically for expanding the current knowledge of wine chemistry.

Phenolics and their antifungal role in grapevine wood decay: focus on the Botryosphaeriaceae family.

The interaction between Vitis vinifera and trunk disease fungi requires better understanding. We studied the role of phenolics as possible plant defense compounds in this context. The impact of 24 grapevine phenolic compounds was determined on 6 major wood decay fungi by an in vitro agar plate assay. Hydroxystilbenoids, especially oligomers such as miyabenol C, isohopeaphenol, and vitisin A and B, greatly reduced the growth of the fungi, except that of Phaeoacremonium aleophilum . A detailed investigation in 10 Botryosphaeriaceae strains revealed that all of the studied members of this family display a common susceptibility to phenolics that is more or less significant. Then we undertook a quantitative analysis of stilbenoid content in grapevine plantlets inoculated with Botryosphaeriaceae to investigate whether in planta these fungi have to counteract the most active phenolics. On the basis of our results, the possible role of phenolics in grapevine defense against trunk disease agents is discussed.

Isolation of powerful antioxidants from the medicinal halophyte Limoniastrum guyonianum.

The antioxidant capacities of the crude extract, aqueous and ethyl acetate partitions of Limoniastrum guyonianum Boiss. (Zita) were investigated in this study. The ethyl acetate phase exhibited a significant antioxidant activity as judged by total antioxidant activity, DPPH test and reducing power. Fractionation of this extract by centrifugal partition chromatography (CPC) using quaternary Arizona solvent systems composed of n-heptane/ethyl acetate/methanol/water led to ten fractions. The antioxidant capacities of these fractions were assessed using the same previous tests. Fraction 8 showed the highest antioxidant capacity (1291.1mg GAE/g DR), the power ability to quench DPPH radical (IC(50)=2µg/ml) and to reduce Fe(3+) (EC(50)=65µg/ml). From this fraction, three powerful flavonoids were isolated (1-3): gallocatechin (1), epigallocatechin (2) and epigallocatechin-3-O-gallate (3). These findings suggest that the antioxidative property of L. guynianum is may be related to the presence of these flavonoids, which can be used in various industrial fields.

Determination of stilbene derivatives in Burgundy red wines by ultra-high-pressure liquid chromatography.

The polyphenols, for example stilbenes and flavonoids, are an important family of compounds present in grapes and wines. Several studies have shown that stilbenes are antioxidants and cancer-preventing agents. For the first time, eight natural stilbenes (trans-resveratrol, trans-piceid, cis-piceid, trans-astringin, trans-piceatannol, (+)-trans-ε-viniferin, pallidol, and hopeaphenol), isolated and purified from Vitis vinifera, were simultaneously analysed by ultra-high-pressure liquid chromatography coupled with photodiode-array detection. Separation of the stilbenes by UHPLC was optimized with the assistance of "Quality-by-Design" commercial software. Four different reversed-phase columns packed with 1.5-1.7-µm particles were tested and compared for their retention behaviour and separation efficiency. On the basis of the performance characteristics determined, the VisionHT C18 HL column was selected for the stilbenes studied, because resolution of the critical pair was 1.5 with a peak width of 2-4 s. The optimized method resulted in highly repeatable retention times (RSD 0.03-0.07%), peak areas (RSD 3-6%), and linear ranges were between 0.005 and 50 mg L(-1) for most of the compounds. All stilbenes, except trans-astringin, trans-piceatannol, and pallidol were identified and quantified in Burgundy red wines at different concentrations after direct injection of the wines.

Protective effect of ε-viniferin on ß-amyloid peptide aggregation investigated by electrospray ionization mass spectrometry.

Abnormal ß-amyloid peptide accumulation and aggregation is considered to be responsible for the formation and cerebral deposition of senile plaques in the brains of patients with Alzheimer's disease (AD). Inhibition of the formation of ß-amyloid (Aß) fibrils would be an attractive therapeutic target for the treatment of AD. Resveratrol and its derivatives exhibit a broad range of pharmacological properties such as protection against cardiovascular diseases and cancers, as well as promoting antiaging effects. We reported previously that ε-viniferin glucoside (VG), a resveratrol-derived dimer, strongly inhibits Aß (25-35) fibril formation in vitro. In this study, we investigated the effects of VG on the aggregation of the full-length peptides (Aß (1-40) and Aß (1-42)) and on the ß-amyloid-induced toxicity in PC12 cells. VG inhibited Aß cytotoxicity and the non-covalent complex between VG and Aß was observed by electrospray ionization mass spectrometry.

Water deficit increases stilbene metabolism in Cabernet Sauvignon berries.

The impact of water deficit on stilbene biosynthesis in wine grape (Vitis vinifera) berries was investigated. Water deficit increased the accumulation of trans-piceid (the glycosylated form of resveratrol) by 5-fold in Cabernet Sauvignon berries but not in Chardonnay. Similarly, water deficit significantly increased the transcript abundance of genes involved in the biosynthesis of stilbene precursors in Cabernet Sauvignon. Increased expression of stilbene synthase, but not that of resveratrol-O-glycosyltransferase, resulted in increased trans-piceid concentrations. In contrast, the transcript abundance of the same genes declined in Chardonnay in response to water deficit. Twelve single nucleotide polymorphisms (SNPs) were identified in the promoters of stilbene synthase genes of Cabernet Sauvignon, Chardonnay, and Pinot Noir. These polymorphisms resulted in eight changes within the predicted cis regulatory elements in Cabernet Sauvignon and Chardonnay. These results suggest that cultivar-specific molecular mechanisms might exist that control resveratrol biosynthesis in grapes.

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.