title: Production and Isomeric Distribution of Xanthylium Cation Pigments and Their Precursors in Wine-like Conditions: Impact of Cu(II), Fe(II), Fe(III), Mn(II), Zn(II), and Al(III).
abstract: This study establishes the influence of Cu(II), Fe(II), Fe(III), Zn(II), Al(III), and Mn(II) on the oxidative production of xanthylium cations from (+)-catechin and either tartaric acid or glyoxylic acid in model wine systems. The reaction was studied at 25 °C using UHPLC and LC-HRMS for the analysis of phenolic products and their isomeric distribution. In addition to the expected products, a colorless product, tentatively assigned as a lactone, was detected for the first time. The results show the importance of Fe ions and a synergistic influence of Mn(II) in degrading tartaric acid to glyoxylic acid, whereas the other metal ions had minimal activity in this mechanistic step. Fe(II) and Fe(III) were shown to mediate the (+)-catechin-glyoxylic acid addition reaction, a role previously attributed to only Cu(II). Importantly, the study demonstrates that C-8 addition products of (+)-catechin are promoted by Cu(II), whereas C-6 addition products are promoted by Fe ions.
authors.affiliation: College of Enology, Northwest A&F University , Yangling, Shaanxi 712100, China.|National Wine and Grape Industry Centre , Mambarra Drive, Wagga Wagga, New South Wales 2678, Australia.
authors.forename: Anque
authors.initials: A
authors.lastname: Guo
authors.affiliation: National Wine and Grape Industry Centre , Mambarra Drive, Wagga Wagga, New South Wales 2678, Australia.|School of Agricultural and Wine Sciences, Charles Sturt University , Locked Bag 588, Wagga Wagga, New South Wales 2678, Australia.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Kontoudakis
authors.affiliation: National Wine and Grape Industry Centre , Mambarra Drive, Wagga Wagga, New South Wales 2678, Australia.|School of Chemistry, The University of Melbourne , Melbourne, Victoria 3010, Australia.
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Scollary
authors.affiliation: National Wine and Grape Industry Centre , Mambarra Drive, Wagga Wagga, New South Wales 2678, Australia.|School of Agricultural and Wine Sciences, Charles Sturt University , Locked Bag 588, Wagga Wagga, New South Wales 2678, Australia.
authors.forename: Andrew C
authors.identifier: http://orcid.org/0000-0002-3719-9995
authors.initials: AC
authors.lastname: Clark
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D003116:Color; D003300:Copper / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D006575:Heterocyclic Compounds, 3-Ring / Q000737:chemistry*; D007536:Isomerism; D008345:Manganese / Q000737:chemistry*; D010084:Oxidation-Reduction; D014920:Wine / Q000032:analysis*; D015032:Zinc / Q000737:chemistry*
chemical_list: D002412:Cations; D005290:Ferric Compounds; D005296:Ferrous Compounds; D006575:Heterocyclic Compounds, 3-Ring; C430851:xanthylium; D008345:Manganese; D003300:Copper; D015032:Zinc; D000537:Aluminum Oxide
keywords: (+)-catechin; isomers; metal ions; tartaric acid oxidation; wine color; xanthylium cations