title: Synthesis, isolation, structure elucidation, and color properties of 10-acetyl-pyranoanthocyanins.
abstract: Grape anthocyanins reacted with diacetyl, a secondary metabolite of microorganisms involved in winemaking, to form 10-acetyl-pyranoanthocyanins, a type of anthocyanin-derived pigment similar to other vitisin-type pyranoanthocyanins found in red wines. The structures of 10-acetyl-pyranomalvidin-3-β-O-glucoside and 10-acetyl-pyranopeonidin-3-β-O-glucoside were confirmed by spectroscopic methods (UV-vis, MS/MS, and NMR) after their synthesis and isolation. In contrast to other vitisin-type pyranoanthocyanins, the newly described 10-acetyl-pyranoanthocyanins exhibited differentiated color-related properties. They showed an important tendency to occur as colorless hemiacetals at C-10 under wine pH conditions, while co-occurrence of flavylium cation and quinoidal base yielded a broad visible absorbance band around 510-520 nm. Moreover, they easily reacted with bisulfite in acidic aqueous solution (pH 2.0), but the expected bleaching was not observed. Bisulfite bonded to the carbonyl of 10-acetyl substituent instead of the expected C-10 position of the pyranoanthocyanin core, thus giving rise to a red pigment hypsochromically shifted toward orangish nuances (maximum absorbances at 487-491 nm).
authors.affiliation: Instituto Regional de Investigación Científica Aplicada, Universidad de Castilla-La Mancha, Campus Universitario s/n, 13071 Ciudad Real, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Gómez-Alonso
authors.forename: Dora
authors.initials: D
authors.lastname: Blanco-Vega
authors.forename: M Victoria
authors.initials: MV
authors.lastname: Gómez
authors.forename: Isidro
authors.initials: I
authors.lastname: Hermosín-Gutiérrez
mesh_terms: D000872:Anthocyanins / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification*; D060326:Chemistry Techniques, Synthetic; D003116:Color; D005960:Glucosides / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013056:Spectrophotometry, Ultraviolet; D053719:Tandem Mass Spectrometry; D014920:Wine
chemical_list: C585868:10-acetyl-pyranomalvidin-3-beta-O-glucoside; C585867:10-acetyl-pyranopeonidin-3-beta-O-glucoside; D000872:Anthocyanins; D005960:Glucosides; C065861:malvidin; C473205:peonidin