Flavonoid condensation reactions with acetaldehyde are particularly important in plants and plant transformation products. In particular, these reactions are involved in color and taste changes occurring during wine ageing and in persimmon de-astringency and some of their products have been detected in cranberry extracts. These reactions have not been fully characterized because of difficulties in extracting and separating resulting products. Model solutions mimicking food products constitute a simplified medium for their exploration, allowing the detection of the newly formed compounds and their structure elucidation. In this work, the reactions of (-)-epicatechin and/or malvidin-3-O-glucoside in the presence of acetaldehyde were studied in model solution systems by ultra-high performance liquid chromatography coupled to linear trap quadrupole-Orbitrap-high resolution mass spectrometry (UPLC-LTQ-Orbitrap-HRMS). A combination of accurate mass database matching and petroleomics-derived data interpretation strategies, namely Kendricks mass defect plots and Van Krevelen 2D and 3D graphs, were used to detect series of compounds arising from these reactions. After applying restriction rules to the HRMS data, more than 65 products were found after reaction of (-)-epicatechin and acetaldehyde and more than 150 products when malvidin-3-O-glucoside was also present in the reaction medium. The products included the expected homogeneous and heterogeneous bridged oligomers, pyranomalvidin-3-O-glucoside, epicatechin–pyranomalvidin-3-O-glucoside, as well as new products (e.g. xanthylium salt derivatives, and all possible combinations of epicatechin, malvidin-3-O-glucoside, ethyl bridges, pyranomalvidin-3-O-glucoside, and xanthylium salt building blocks). With all these structures, it is possible to develop a structural model for acetaldehyde-mediated reactions than can be monitored in complex systems such as wine.

High-resolution mass spectrometry analysis of flavonoid-acetaldehyde reaction products in wine-like model solutions

253rd National Meeting (2017)

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