New Precursors to 3-Sulfanylhexan-1-ol? Investigating the Keto–Enol Tautomerism of 3-<i>S</i>-Glutathionylhexanal

• Main Authors: Jennifer R. Muhl, Lisa I. Pilkington, Rebecca C. Deed
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Molecules
• Subjects: 3-sulfanylhexan-1-ol; aroma compound precursors; white wine; deuterium exchange; tautomerism
• Online Access: https://www.mdpi.com/1420-3049/26/14/4261

The volatile thiol compound 3-sulfanylhexan-1-ol (3SH) is a key impact odorant of white wines such as Sauvignon Blanc. 3SH is produced during fermentation by metabolism of non-volatile precursors such as 3-<i>S</i>-gluthathionylhexanal (glut-3SH-al). The biogenesis of 3SH is not fully understood, and the role of glut-3SH-al in this pathway is yet to be elucidated. The aldehyde functional group of glut-3SH-al is known to make this compound more reactive than other precursors to 3SH, and we are reporting for the first time that glut-3SH-al can exist in both keto and enol forms in aqueous solutions. At wine typical pH (~3.5), glut-3SH-al exists predominantly as the enol form. The dominance of the enol form over the keto form has implications in terms of potential consumption/conversion of glut-3SH-al by previously unidentified pathways. Therefore, this work will aid in the further elucidation of the role of glut-3SH-al towards 3SH formation in wine, with significant implications for the study and analysis of analogous compounds.