Isolation and Structural Characterization of New Acylated Anthocyanin−Vinyl−Flavanol Pigments Occurring in Aging Red Wines

Three newly formed pigments were detected and isolated from a 2-year-old Port wine through TSK Toyopearl HW-40(S) gel column chromatography and characterized by UV−visible spectrophotometry, NMR, and mass spectrometry (ESI/MS). 1H NMR and 13C NMR data for these pigments obtained using 1D and 2D NMR techniques (COSY, NOESY, gHSQC, and gHMBC) are reported for the first time. The structure of the pigments was found to correspond to the vinyl cycloadducts of malvidin 3-coumaroylglucoside bearing either a procyanidin dimer or a flavanol monomer ((+)-catechin or (−)-epicatechin). Additionally, conformational analysis was performed for one of these newly formed pigment using computer-assisted model building and molecular mechanics. A chemical nomenclature is proposed to unambiguously name this new family of anthocyanin-derived pigments. Keywords: Red wine; flavanol; aging; pigments; anthocyanins; isomers; NMR; mass spectrometry