Interactions between catechin and malvidin-3-monoglucoside in model solutions

Abstract

The interaction between (+)-catechin and malvidin-3-monoglucoside was studied in model solutions at pH values of 3.2 and 4 over a 30-day period at 32 °C. With time, a progressive browning, accompanied by a hypso-chromic shift in their visible absorption maxima, was observed in the solutions. This was attributed to the formation of yellow pigments showing spectra with absorption maxima ranging between 425 nm and 455 nm, as detected by HPLC/DAS. A mechanism is proposed for the formation of these pigments, according to which the anthocyanin in flavylium form would bind through its C-4 to C-8 of catechin to give a colourless condensed flavene, which through an oxidative mechanism would later become rearranged to a xanthylium-like derivative. A degradation process of the anthocyanin was seen to overlap that of condensation. Syringic acid was detected as being released from the anthocyanin degradation. When the solutions were conserved at 15 °C, all the processes were reduced and minor modifications occurred during the assay period.