Characterization of Kinetic and Thermodynamic Parameters of Cyanidin-3-glucoside Methyl and Glucuronyl Metabolite Conjugates

The determination of rate and equilibrium constants of anthocyanin metabolites with in vivo occurrence, cyanidin-4'-O-methyl-3-glucoside (Cy4'Me3glc) and cyanidin-7-O-glucuronyl-3-glucoside (Cy7Gluc3glc), was carried out for the first time by means of direct and reverse pH jumps. The thermodynamics and kinetics of these compounds are similar to the anthocyanin monoglucosides in particular for the analogous cyanidin-3-glucoside (Cy3glc) and peonidin-3-glucoside (Peo3glc). The rate and equilibrium constants of metabolites were also compared with malvin (malvidin 3,5-diglucoside) and with a bioinspired compound 3',4'-dihydroxy-7-O-glucopyranosyloxyflavylium (DGF). In Cy4'Me3glc and Cy7Gluc3glc the rate of hydration for a fixed pH value is slower than in DGF and the dominant species at moderately acidic solutions is the hemiketal. Oppositely, in DGF trans-chalcone is the dominant species at moderately acidic solutions.