Identification by mass spectrometry of new compounds arising from the reactions involving malvidin-3-glucoside-(O)-catechin, catechin and malvidin-3-glucoside.

The aim of this work was to study the putative reactions that could occur in red wines between malvidin-3-glucoside-(O)-catechin (mv3glc-(O)-cat) adduct and catechin (cat) or malvidin-3-glucoside (mv3glc) in presence of acetaldehyde. Mv3glc-(O)-cat adduct (1 mM) was incubated with catechin (or mv3glc) in the presence of acetaldehyde (molar ratio of 1:4:10) in 12% ethanol/water at pH 3.2, protected from light and placed in the oven at 30 °C. The formation of the new compounds was monitored by liquid chromatography-diode-array detection/electrospray ionization mass spectrometry (LC-DAD/ESI-MS) analysis in the positive and negative ion mode. The LC-DAD/ESI-MS characterization allowed the confirmation of the structures of the methylmethine-linked cat-mv3glc-(O)-cat ([M-H](-) m/z 1097) and mv3glc-mv3glc-(O)-cat ([M](+) m/z 1301) adducts. The studies performed in model solutions showed that the colorless mv3glc-(O)-cat adduct can undergo some of the characteristic reactions of anthocyanins and flavan-3-ols that occur in red wine in the presence of acetaldehyde forming new methylmethine-bridged compounds.