Antioxidant and Cytoprotective Activities of Grapevine Stilbenes.

Grapevine stem extracts are viticulture byproducts rich in stilbenes that are increasingly studied for their potential biological activities. This study aimed to investigate some biological activities of a grape byproduct with high stilbenoid content and to point out the molecules responsible of these beneficial activities. As a consequence, the extract was subjected to a bioguided fractionation and separation by centrifugal partition chromatography. The obtained fractions were characterized by liquid chromatography coupled to mass spectrometry and nuclear magnetic resonance. Fractions were purified further by column chromatography and resulted in the purification of the main constituents. Thirteen stilbenes have been quantified. The most abundant compounds were ε-viniferin, resveratrol, and, in lesser amounts, isohopeaphenol and ampelopsin A. The extract, fractions, and major stilbenes were tested for their antioxidant activity by oxygen radical absorbance capacity and their cyprotective effects against β-amyloid on rat pheochromocytoma cells. Among them, fraction 5 showed significant antioxidant activity and fraction 2 had a significant cytoprotective effect against β-amyloid-induced toxicity. Two putative inhibitors of β-amyloid toxicity have been identified: ampelopsin A and piceatannol.