Identification of adducts between an odoriferous volatile thiol and oxidized grape phenolic compounds: kinetic study of adduct formation under chemical and enzymatic oxidation conditions

J Agric Food Chem. 2012 Mar 14;60(10):2647-56. doi: 10.1021/jf204295s. Epub 2012 Mar 1.


HPLC-MS and (1)H, (13)C, and 2D NMR analyses were used to identify new addition products between 3-sulfanylhexan-1-ol (3SH) and o-quinones derived from (+)-catechin, (-)-epicatechin, and caftaric acid. The kinetics of formation of these adducts were monitored in a wine model solution and in a must-like medium by HPLC-UV-MS with the aim of understanding the chemical mechanism involved in reactions between volatile thiols and o-quinones. One o-quinone-caftaric acid/3SH adduct, three o-quinone-(+)-catechin/3SH adducts, and three o-quinone-(-)-epicatechin/3SH adducts were characterized. Caftaric acid was oxidized faster than (-)-epicatechin and (+)-catechin when these phenolic compounds were incubated in a one-component mixture with polyphenoloxidase (PPO) in the presence of 3SH. Consequently, o-quinone-caftaric acid formed adducts with 3SH more rapidly than o-quinone-(+)-catechin and o-quinone-(-)-epicatechin in the absence of other nucleophilic species. Furthermore, o-quinone-(-)-epicatechin reacted faster than o-quinone-(+)-catechin with 3SH. Sulfur dioxide decreased the yield of adduct formation to a significant extent. Under chemical oxidation conditions, the rates and yields of adduct formation were lower than those observed in the presence of PPO, and o-quinone-caftaric acid was slightly less reactive with 3SH, compared to oxidized flavan-3-ols. The identification of o-quinone-caftaric acid/3SH and o-quinone-(+)-catechin/3SH adducts in a must matrix suggests that the proposed reaction mechanism is responsible for 3SH loss in dry wines during their vinification and aging process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catechol Oxidase / chemistry
  • Catechol Oxidase / metabolism*
  • Kinetics
  • Molecular Structure
  • Oxidation-Reduction
  • Phenols / chemistry
  • Phenols / metabolism*
  • Plant Extracts / chemistry
  • Plant Extracts / metabolism*
  • Plant Proteins / chemistry
  • Plant Proteins / metabolism*
  • Sulfhydryl Compounds / chemistry
  • Sulfhydryl Compounds / metabolism*
  • Vitis / chemistry
  • Vitis / enzymology*
  • Vitis / metabolism
  • Volatile Organic Compounds / chemistry*


  • Phenols
  • Plant Extracts
  • Plant Proteins
  • Sulfhydryl Compounds
  • Volatile Organic Compounds
  • Catechol Oxidase
  • caftaric acid