Isolation of Hydrolyzable Tannins from <i>Castanea sativa</i> Using Centrifugal Partition Chromatography

Castanea sativa wood is a rich source of hydrolyzable tannins, known for their diverse bioactivities. To investigate these bioactive properties further, it is crucial to isolate and characterize hydrophilic compounds effectively. To address this issue, we developed a centrifugal partition chromatography (CPC) method and applied it to an aqueous C. sativa wood extract. We determined the partition coefficients (KD) of the six major compounds using four butanol-/water-based biphasic solvent systems. Initially, we utilized the n-butanol/propanol/water (3:1:4, v/v/v) systems for the first fractionation step. Subsequently, we employed the water/methyl tert-butyl ether/butanol/acetone (8:5:3:4, v/v/v/v) system to fractionate moderately and highly hydrophilic fractions. We calculated the KD values for major compounds of the most hydrophilic fractions using the butanol/ethanol/water (4:1:5, v/v/v) and butanol/isopropanol/water (2:1:3, v/v/v) systems. In total, we isolated 23 compounds through a combination of CPC, size exclusion chromatography, and preparative HPLC. Among these compounds, six have never been previously described. We characterized them by 1D and 2D NMR experiments and high-resolution mass spectroscopy acquisitions

Comparison of the Impact of Two Molecules on Plant Defense and on Efficacy against <i>Botrytis cinerea</i> in the Vineyard: A Plant Defense Inducer (Benzothiadiazole) and a Fungicide (Pyrimethanil)

Grapevine is subject to diseases that affect yield and wine quality caused by various pathogens including <i>Botrytis cinerea</i>. To limit the use of fungicides, an alternative is to use plant elicitors such as benzothiadiazole (BTH). We investigated the effect of a fungicide (Pyrimethanil) and an elicitor (benzothiadiazole) on plant defenses. Applications for two consecutive years in the vineyard significantly reduced gray mold. Two and seven days after treatments, the expressions of 48 genes involved in defenses showed differential modulation (up- or down-regulation) depending on treatment. Some genes were identified as potential markers of protection and were linked to an increase in total polyphenols (TP) in leaves. Surprisingly, the fungicide also induced the expression of defense genes and increased the polyphenol content. This suggests that BTH acts as an efficient elicitor in the vineyard and that Pyrimethanil may act, in part, as a defense-inducing agent on the vine

Hyphenating Centrifugal Partition Chromatography with Nuclear Magnetic Resonance through Automated Solid Phase Extraction

Centrifugal partition chromatography (CPC) and all countercurrent separation apparatus provide chemists with efficient ways to work with complex matrixes, especially in the domain of natural products. However, despite the great advances provided by these techniques, more efficient ways of analyzing the output flow would bring further enhancement. This study describe a hyphenated approach made by coupling NMR with CPC through a hybrid-indirect coupling made possible by using a solid phase extraction (SPE) apparatus intended for high-pressure liquid chromatography (HPLC)-NMR hyphenation. Some hardware changes were needed to adapt the incompatible flow-rates and a reverse-engineering approach that led to the specific software required to control the apparatus. 1D ¹HNMR and ¹H–¹H correlation spectroscopy (COSY) spectra were acquired in reasonable time without the need for any solvent-suppression method thanks to the SPE nitrogen drying step. The reduced usage of expensive deuterated solvents from several hundreds of milliliters to the milliliter order is the major improvement of this approach compared to the previously published ones

Viniphenol A, a Complex Resveratrol Hexamer from <i>Vitis vinifera</i> Stalks: Structural Elucidation and Protective Effects against Amyloid-β-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 <i>Vitis vinifera</i> 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 (<b>1</b>), a new resveratrol hexamer, was isolated along with five oligostilbenoids identified in <i>V. vinifera</i> for the first time, ampelopsin C, davidiol A, leachianol F, leachianol G, and <i>E</i>-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-β-induced toxicity in PC12 cell cultures

Stilbenes from <i>Vitis vinifera</i> L. Waste: A Sustainable Tool for Controlling <i>Plasmopara Viticola</i>

Stilbene-enriched extracts from <i>Vitis vinifera</i> waste (cane, wood, and root) were characterized by UHPLC-MS. Eleven stilbenes were identified and quantified as follows: ampelopsin A, (<i>E</i>)-piceatannol, pallidol, (<i>E</i>)-resveratrol, hopeaphenol, isohopeaphenol, (<i>E</i>)-ε-viniferin, (<i>E</i>)-miyabenol C, (<i>E</i>)-ω-viniferin, <i>r</i>2-viniferin, and <i>r</i>-viniferin. The fungicide concentration inhibiting 50% of growth of <i>Plasmopara viticola</i> sporulation (IC₅₀) was determined for the extracts and also for the main compounds isolated. <i>r</i>-Viniferin followed by hopeaphenol and <i>r</i>2-viniferin showed low IC₅₀ and thus high efficacy against <i>Plasmopara viticola.</i> Regarding stilbene extracts, wood extract followed by root extract showed the highest antifungal activities. These data suggest that stilbene complex mixtures from <i>Vitis vinifera</i> waste could be used as a cheap source of bioactive stilbenes for the development of natural fungicides

Stilbenoid Profiles of Canes from <i>Vitis</i> and <i>Muscadinia</i> Species

We present stilbenoid profiles of canes from 16 grapevines. Fifteen stilbenoids were obtained through isolation and structure identification using MS, NMR, and [α]_D or as commercial standards. An HPLC–UV method for the simultaneous quantification of nine of these stilbenoids was developed and applied to canes of <i>Vitis amurensis</i>, <i>Vitis arizonica</i>, <i>Vitis berlandieri</i>, <i>Vitis betulifolia</i>, <i>Vitis cinerea</i>, <i>Vitis</i> × <i>champini</i>, <i>Vitis</i> × <i>doaniana</i>, <i>Vitis labrusca</i>, <i>Vitis candicans</i> (syn. <i>Vitis mustangensis</i>), <i>Vitis riparia</i>, <i>Vitis rupestris</i>, <i>Vitis vinifera</i>, <i>Muscadinia rotundifolia</i>, and a <i>V. vinifera</i> × <i>M</i>. <i>rotundifolia</i> hybrid. In these species, <i>E</i>-ampelopsin E, <i>E</i>-amurensin B, <i>E</i>-piceid, <i>E</i>-piceatannol, <i>E</i>-resveratrol, <i>E</i>-resveratroloside, <i>E</i>-ε-viniferin, <i>E</i>-ω-viniferin, and <i>E</i>-vitisin B were quantified, when found in sufficient amounts. Total concentrations ranged from ∼2.2 to 19.5 g/kg of dry weight. Additional stilbenoids, <i>E</i>-3,5,4′-trihydroxystilbene 2-<i>C</i>-glucoside, <i>Z</i>-ampelopsin E, <i>Z</i>-<i>trans</i>-miyabenol C, <i>E</i>-<i>trans</i>-miyabenol C, scirpusin A, and <i>Z</i>-vitisin B, were identified but not quantified. Our results indicate that canes, particularly those of non-<i>vinifera</i> species, have substantial quantities of valuable, health-promoting stilbenoids

Unambiguous Determination of the Absolute Configuration of Dimeric Stilbene Glucosides from the Rhizomes of <i>Gnetum africanum</i>

Dimeric stilbene glucosides <b>1</b>–<b>3</b> [two diastereomers of (−)-gnemonoside A (<b>1a</b> and <b>1b</b>), (−)-gnemonoside C (<b>2</b>), and (−)-gnemonoside D (<b>3</b>)] as well as a mixture of the two enantiomers of gnetin C (<b>4</b>) were isolated from the rhizomes of <i>Gnetum africanum</i>. The two enantiomers of gnetin C, (+)-<b>4</b> and (−)-<b>4</b>, were obtained from the aglycones of <b>1a</b> and <b>1b</b>, respectively. The configurations of these stilbenoids were investigated by NMR and vibrational circular dichroism (VCD) experiments. The absolute configurations of (−)-<b>1a</b>, (−)-<b>2</b>, (−)-<b>3</b>, and (−)-<b>4</b> were established as 7a<i>S</i>,8a<i>S</i> by VCD spectroscopy in combination with density functional theory calculations. The antiamyloidogenic activity of the isolated stilbenes was also evaluated versus beta-amyloid fibrils. The four glucosides of gnetin C (<b>1a</b>, <b>1b</b>, <b>2</b>, and <b>3</b>) were found to be the most active compounds, with inhibition percentages of 56, 56, 58, and 54 at 10 μM, respectively