title: The formation of wine lactone from grape-derived secondary metabolites.
abstract: Wine lactone (i.e., 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one, 1a/1b) was formed hydrolytically at wine pH from both racemic (E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid (3) and the corresponding glucose ester 2a at 45 °C but at room temperature was only formed from the acid 3. The glucose ester does not appear to be a significant precursor for the formation of wine lactone in wine. The slow formation of wine lactone from the free acid 3 indicates that the acid is not likely to be an important precursor to wine lactone in young wines unless present in high concentration (≫ 1 mg/L), but could be a significant precursor to wine lactone in wine that is several years old. The wine lactone formed in hydrolysates of the (6R)-enantiomer of 3 was partially enriched in the (3S,3aS,7aR)-enantiomer 1a when the hydrolysis was conducted at pH 3.2 and 100 °C in a closed vessel or under simultaneous distillation-extraction (SDE) conditions, and the enantiomeric excess (ee) varied from 5 to 22%. Hydrolysis of (6R)-3 in sealed ampules at 45 °C and at pH 3.0, 3.2, or 3.4 gave near-racemic wine lactone, but when the hydrolyses were conducted at room temperature, the product was enriched in the (3S,3aS,7aR)-enantiomer 1a and the ee was greater at higher pH (up to 60% at pH 3.4).
authors.affiliation: School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA 5064, Australia.
authors.forename: Joanne
authors.initials: J
authors.lastname: Giaccio
authors.forename: Dimitra L
authors.initials: DL
authors.lastname: Capone
authors.forename: Anders E
authors.initials: AE
authors.lastname: Håkansson
authors.forename: Heather E
authors.initials: HE
authors.lastname: Smyth
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Elsey
authors.forename: Mark A
authors.initials: MA
authors.lastname: Sefton
authors.forename: Dennis K
authors.initials: DK
authors.lastname: Taylor
mesh_terms: D007783:Lactones / Q000737:chemistry* / Q000378:metabolism*; D013237:Stereoisomerism; D027843:Vitis / Q000737:chemistry* / Q000378:metabolism; D014920:Wine / Q000032:analysis*
chemical_list: D007783:Lactones