title: Hemisynthesis and structural characterization of flavanol-(4,8)-vitisins by mass spectrometry.
abstract: Vitisins constitute the major group of pyranoanthocyanins naturally occurring in red wines. Regarding their chemical structure, only carboxypyranoanthocyanins have been detected and quantified in red wines, but no vitisin with substitutions in the carbons of the A ring has been identified. However, considering the chemical reactions that take place in red wine, the existence of flavan-3-ol-(4,6/8)-vitisins is expected. This paper reports for the first time the structural identification of catechin-vitisin A and catechin-vitisin B based on their mass data and fragmentation patterns. This work also provides some chromatographic and visible spectroscopic features of these pigments and documents the existence of both in red table wines. Moreover, it is also proposed that Cat-Vit A pigments arise from the cycloaddition of pyruvic acid to an anthocyanin moiety of a flavanol-anthocyanin adduct rather than by direct nucleophilic attack of a vitisin A on the carbocation C(4) of catechin.
authors.affiliation: Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: Frederico
authors.initials: F
authors.lastname: Nave
authors.forename: Natércia
authors.initials: N
authors.lastname: Teixeira
authors.forename: Nuno
authors.initials: N
authors.lastname: Mateus
authors.forename: Victor
authors.initials: V
authors.lastname: de Freitas
mesh_terms: D001572:Benzofurans / Q000138:chemical synthesis / Q000737:chemistry*; D002392:Catechin / Q000138:chemical synthesis / Q000737:chemistry*; D013058:Mass Spectrometry; D015394:Molecular Structure; D010636:Phenols / Q000138:chemical synthesis / Q000737:chemistry*; D014920:Wine / Q000032:analysis
chemical_list: D001572:Benzofurans; D010636:Phenols; C480486:malvidin-3-O-glucoside-4 vinyl; C412469:vitisin A; D002392:Catechin