Resveratrol and Its Oligomers from Wine Grapes Are Selective ¹O₂ Quenchers: Mechanistic Implication by High-Performance Liquid Chromatography−Electrospray Ionization−Tandem Mass Spectrometry and Theoretical Calculation

Abstract

Resveratrol and its oligomers, abundantly present in wine grapes, are believed to be effective phytoalexins for the phenomenon "French paradox" partially by virtue of their powerful antiradical properties. EPR spin-trapping technique was utilized, demonstrating all polyphenols were selective (1)O2 quenchers but not effective (•)OH and O2(•¯) scavengers. On the basis of the HPLC-ESI-MS(2) analysis for the simulated reactions of polyphenols with (1)O2, the molecular weights of the resulting photochemical products were 14 or 28 Da higher than those of their substrates. No fragment C2H2O (42 Da), which was rather distinctive of the resorcinol rings in these cases, had been observed, whereas their MS/MS spectra displayed characteristic neutral fragments including carbon monoxide (CO, 28 Da) and 2-hydroxy[1,4]benzoquinone (C6H4O3, 124 Da). Finally, PM3 semiempirical calculations and HR-FTICR-MS experiments were performed, supporting the assertion that their quenching mechanism involved physical and chemical pathways. Chemical quenching underwent an endoperoxide intermediate form to generate quinones.

Wine and grape polyphenols—A chemical perspective

“…ε-viniferin, Fig. 7) were also identified in grapevine leaves and wine by-products (Jiang et al, 2010;Lima et al, 1999;Moreno-Labanda et al, 2004;Pezet et al, 2003;Püssa et al, 2006;Vitrac et al, 2005).…”

Wine and grape polyphenols—A chemical perspective

“…Fig. 7 comprises stilbenes that have recently been identified in both grapes and wine: piceid, piceatannol glucoside (usually named astringin), pterostilbene, pallidol, parthenocissin and ameurensin G (Jiang, He, Jiang, Sun, & Pan, 2010). Oligomeric forms of the oxidation products of resveratrol-viniferins (e.g.…”

Carbon-Carbon Double Bond and Resorcinol in Resveratrol and Its Analogues: What Is the Characteristic Structure in Quenching Singlet Oxygen?

“…According to their work, the characteristic structure in the process of resveratrol quenching 1 O 2 is the carbon-carbon double bond. However, Jiang et al (2010) reported that resveratrol quinone ( 1-2 ) was the main product responsible for quenching 1 O 2 and suggested that what really matters in the mechanism is the resorcinol moiety [20]. In addition, according to our previous result [22], the carbon-carbon double bond and resorcinol moiety both were verified to be participants in the quenching reaction.…”

“…In the further investigation of the activity of stilbenes quenching 1 O 2 , many works so far have focused on its mechanism. Some hold the view that resorcinol ring could be oxidized to quinone when resveratrol quenches 1 O 2 [20]. Others propose that the mechanism of resveratrol 1 O 2 quenching is mainly because of the carbon-carbon double bond based on nuclear magnetic resonance (NMR) data [21].…”