16727-30-3Relevant academic research and scientific papers
Thermodynamics and kinetics of flavylium salts: Malvin revisited
Pina, Fernando
, p. 2109 - 2116 (1998)
The pH-dependent structural transformations in aqueous solutions of natural and synthetic flavylium salts are re-examined. The procedure uses Malvin as a reference compound and exploits the different timescales of the kinetic process that take place prior to the equilibration. For each process a kinetic expression was deduced allowing calculation of all the equilibrium constants and most of the rate constants of the system. The equilibrium constants were confirmed by comparison with the data obtained by 1H NMR. Clear evidence for the formation of significant amounts of trans-chalcone in Malvin was obtained.
ELUCIDATION OF THE MULTIPLE EQUILIBRIA OF MALVIN IN AQUEOUS SOLUTION BY ONE- AND TWO-DIMENSIONAL NMR
Santos, Helena,Turner, David L.,Lima, Joao C.,Figueiredo, Paulo,Pina, Fernando S.,Macanita, Antonio L.
, p. 1227 - 1232 (2007/10/02)
One- and two-dimensional NMR were used to characterize the several forms of malvin present in aqueous solution in the pH range 0.3-4.5 and to determine their molar fractions as a function of pH.In addition to the flavylium cation, two hemiacetal forms and both the cis and trans form of chalcone were firmly identified.The pathways for the interconversion of different forms were derived and and the molar absorbances of the species calculated by coupling NMR and UV/Vis data.Equilibrium constants were determined at different temperatures, and enthalpy and entropy changes were calculated for the interconversion processes.The conclusions are supported by molecular orbital calculations. Key words: Anthocyanins; malvin; multi-equilibria; two-dimensional NMR.
