title: Measuring protection of aromatic wine thiols from oxidation by competitive reactions vs wine preservatives with ortho-quinones.
abstract: Quinones are central intermediates in wine oxidation that can degrade the quality of wine by reactions with varietal thiols, such as 3-sulfanylhexanol, decreasing desirable aroma. Protection by wine preservatives (sulphur dioxide, glutathione, ascorbic acid and model tannin, phloroglucinol) was assessed by competitive sacrificial reactions with 4-methyl-1,2-benzoquinone, quantifying products and ratios by HPLC-UV-MS. Regioselectivity was assessed by product isolation and identification by NMR spectroscopy. Nucleophilic addition reactions compete with two electron reduction of quinones by sulphur dioxide or ascorbic acid, and both routes serve as effective quenching pathways, but minor secondary products from coupled redox reactions between the products and reactants are also observed. The wine preservatives were all highly reactive and thus all very protective against 3-sulfanylhexanol loss to the quinone, but showed only additive antioxidant effects. Confirmation of these reaction rates and pathways in wine is needed to assess the actual protective action of each tested preservative.
authors.affiliation: Department of Viticulture and Enology, University of California, Davis, CA 95616, United States.
authors.forename: Maria
authors.initials: M
authors.lastname: Nikolantonaki
authors.affiliation: Department of Pharmacognosy and Natural Products Chemistry, Faculty of Pharmacy, University of Athens, Panepistimioupolis Zografou 15 771, Athens, Greece.
authors.forename: Prokopios
authors.initials: P
authors.lastname: Magiatis
authors.affiliation: Department of Viticulture and Enology, University of California, Davis, CA 95616, United States. Electronic address: alwaterhouse@ucdavis.edu.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Waterhouse
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D016227:Benzoquinones / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D005520:Food Preservatives / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D014920:Wine / Q000032:analysis*
chemical_list: D000975:Antioxidants; D016227:Benzoquinones; D005520:Food Preservatives; D013438:Sulfhydryl Compounds; C088487:4-methyl-1,2-benzoquinone
keywords: Antioxidants; Ascorbic acid; Glutathione; Nucleophiles; Oxidation; Quinones; Reactivity; Sulphur dioxide; Wine