Impact of Glutathione on the Formation of Methylmethine- and Carboxymethine-Bridged (+)-Catechin Dimers in a Model Wine System

Abstract

This study was performed to assess the impact of glutathione on the reaction between (+)-catechin and carbonyl compounds in wine-related conditions. (+)-Catechin (0.50 mM) and either glyoxylic acid (0.25 mM) or acetaldehyde (0.25 mM) were added to a model wine system with 0.0, 0.25, and 2.5 mM of glutathione added. UPLC-DAD and LC-MS analysis showed that the formation of carbonyl-bridged (+)-catechin dimers was inhibited in the samples with a glutathione to carbonyl ratio of 10:1 compared to the samples without glutathione. At a ratio of 1:1, glutathione inhibited the acetaldehyde-bridged dimers but only had a minor impact on the glyoxylic acid-bridged dimers. Further investigations showed that this trend of inhibition by glutathione on the glyoxylic acid-derived dimer was independent of temperatures, 20 °C vs 45 °C, or the presence of metal ions, 0.2 mg/L copper(II) and 5 mg/L iron(II). (1)H NMR analysis and LC-MS analysis provided evidence that glutathione inhibited dimer formation via different mechanisms depending on the carbonyl compound. For acetaldehyde-derived dimers, the main mode of inhibition was the ability of glutathione to form a (methyl-glutathionyl-methine)-(+)-catechin complex. Alternatively, the formation of a glutathione-glyoxylic acid addition product impeded the reaction between glyoxylic acid with (+)-catechin. These results demonstrate that glutathione, at sufficient concentration, can have a substantial impact on carbonyl-derived polymerization reactions in wine-like conditions.

Sulfur Dioxide and Glutathione Alter the Outcome of Microoxygenation

“…In the pH range 2-6, lower pH values increase the rate of reaction for SO 2 (Drexler et al 1991), while the oxidation rate of GSH by hydrogen peroxide increases with increasing pH (Finley et al 1981). However, taking into account the low amount of GSH used in this experiment and the high O 2 :GSH molar reaction ratio, it seems that the more relevant effect produced by GSH is due to other reactions than to its reaction with H 2 O 2 , likely due to its capability of reacting rapidly with quinones (Nikolantonaki and Waterhouse 2012) and other organic compounds such as catechin, hydroxycinnamic acids, and carbonyls involved in wine oxidation (Bouzanquet et al 2012, Sonni et al 2011b). …”

“…However, this is the first observation that GSH can inhibit acetaldehyde production in wine oxidation during MOx. It is known that GSH binds acetaldehyde (Sonni et al 2011b) and that oxidation of GSH yields several oxidation products when it reacts with hydrogen peroxide in aqueous solution at pH values close to that of wine (Finley et al 1981). Thus, it seems possible that this molecule exerts a protective function in wine by several possible mechanisms: (i) scavenging hydrogen peroxide, (ii) by direct reaction with wine phenolics (Bouzanquet et al 2012, Sonni et al 2011a by way of quinones (Nikolantonaki and Waterhouse 2012), and (iii) binding acetaldehyde to a less extent with respect to SO 2 (Sonni et al 2011b).…”

Influence of ascorbic acid, sulfur dioxide and glutathione on oxidation product formation in wine-like systems

“…Furthermore, the formation of larger amounts of glyoxylic acid showed that SO 2 was not able to completely prevent the first oxidation step of tartaric acid. However its ability to react with oxidation products inhibits the further reactions involved in xanthylium cation formation probably generating a bisulfite addition product with glyoxylic acid [4]. Regarding the effect of AA addition, there seems to be a competitive effect with the xanthylium cation formation.…”

“…The antioxidative effect of SO 2 is based on the direct reaction with H 2 O 2 as high amounts of SO 4 2-could be detected. Furthermore, the formation of larger amounts of glyoxylic acid showed that SO 2 was not able to completely prevent the first oxidation step of tartaric acid.…”

“…The main anti-oxidative activity of SO 2 is the reaction of the bisulfite ion with H 2 O 2 to form sulfuric acid, changing the oxidation state of sulfur from +IV to +VI, AA can directly react with molecular oxygen to generate dehydroascorbic acid and H 2 O 2 . The reaction of GSH seems to be either via the reaction with active oxygen species to form the glutathione disulfide (GSSG) or to form addition products with carbonyl or o-quinone compounds [3,4]. Negative oxidative evolution of white wines can result in the loss of pleasant aroma compounds, increase in acetaldehyde concentration or oxidative color evolution.…”