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