Structure of a new dimeric acetaldehyde malvidin 3-glucoside condensation product

A new pigment was detected in wine-like model solution containing malvidin 3-O-glucoside and acetaldehyde. This compound was isolated, and its structure was investigated by UV, MS and NMR spectroscopies. The analytical data allowed identification of it to 8,8 methyl methine-linked malvidin 3-O-glucoside dimer. The occurrence of this pigment was demonstrated in red wine. A polymeric fraction was also isolated from the model solution and analysed by LC/MS. Detection of methyl methine-linked malvidin 3-O-glucoside oligomers proved that acetaldehyde mediated self-condensation of anthocyanins is possible, and that the C6 position of anthocyanins seems reactive as the C8 although to a lesser extent.