Isolation and purification of five phenolic compounds from the Xinjiang wine grape (Vitis Vinifera) and determination of their antioxidant mechanism at cellular level

Abstract

Xinjiang wine grapes (Vitis Vinifera) are extraordinarily rich sources of stilbenes. In this study, two pair of isomers of resveratrol dimers trans-e-viniferin (1) and (+)-cis-e-viniferin (2), astilbin (4) and isoastilbin (5), and resveratrol tetramer (−)-hopeaphenol (3) were isolated and purified. Their structures were determined by means of nuclear magnetic resonance and mass spectrometry analysis. Then, cellular antioxidant activity of the five phenolic compounds was evaluated in human hepatoma (Hep G2) cells. Results indicated that (4) has the strongest antioxidant activity (10 µg/mL), while (5) is the weakest one. Mechanism process of antioxidant at genes expression was elaborated by real-time quantitative PCR, which showed that the five stilbenes could down-regulation of oxidative stress genes and apoptosis genes. Therefore, this study provides the useful evidence for these compounds to develop the functional foods and nutritional supplements. Five phenolic compounds, trans-e-viniferin (1) and (+)-cis-e-viniferin (2), astilbin (4) and isoastilbin (5), resveratrol tetramer (−)-hopeaphenol (3) were isolated and purified. These five compounds have a significantly reduced effect on oxidative stress genes at cellular level by real-time quantitative PCR