178941-48-5Relevant academic research and scientific papers
Photochemistry of 3,4′-dimethoxy-7-hydroxyflavylium chloride: Photochromism and excited-state proton transfer
Pina, Fernando,Benedito, Lina,Melo, Maria Joao,Parola, A. Jorge,Bernardo, Alexandra
, p. 1693 - 1699 (1996)
The synthetic compound 3,4′-dimethoxy-7-hydroxyflavylium chloride gives rise, in aqueous solution at moderately acidic pH, to a pH-dependent equilibrium between the flavylium cation, hemiacetal, (Z)-chalcone and a small amount of quinonoidal base. The distribution, as a function of pH, of the molar fractions of the several species present in solution have been calculated on the basis of 1H NMR and pH jump experiments monitored by stopped-flow and conventional UV-VIS spectrophotometry, and high-performance liquid chromatography (HPLC). The compound shows interesting photochemical properties: (i) at pH 4.0 it presents a photochromic effect that converts (Z)-chalcone into hemiacetal, the reaction being reversible in the dark and (ii) excited-state proton transfer is observed between the flavylium cation and quinonoidal base. An appropriate formalism to quantify the experimental results has been developed. The formalism allows determination of the pH-dependent molar fraction distribution of the several anthocyanin forms present at equilibrium, as well as predicting the distribution of the molar fractions prior to equilibrium.
COMPLEXATION OF A FLUORESCENT ANTHOCYANIN WITH PURINES AND POLYPHENOLS
Wigand, Marie Claude,Dangles, Olivier,Brouillard, Raymond
, p. 4317 - 4324 (2007/10/02)
It is demonstrated that the synthetic anthocyanin 7-hydroxy-3,4'-dimethoxyflavylium chloride associates with copigments in a manner which mimics that of natural anthocyanins.When studying copigmentation, 7-hydroxy-3,4'-dimethoxyflavylium chloride offers several advantages over its natural homologues.Firstly, it is easy to prepare pure.Secondly, its unexpected strong fluorescence opens up a new field in copigmentation studies.Finally, being sufficiently water-soluble, its complexation can also be investigated by means of 1H NMR spectroscopy.Copigments investigated are : chlorogenic acid, gallic acid, caffeine, adenosine 5'-monophosphate and adenosine 5'-triphosphate. Key Word Index: Anthocyanin complexation; purines; polyphenols; UV-visible, fluorescence and 1H NMR spectroscopy.
