EXCITED STATES OF ANTHOCYANINS: THE CHALCONE ISOMERS OF MALVIDIN 3,5-DIGLUCOSIDE |
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| Authors: | J C Lima Parvin Danesh Paulo Figueiredo Fernando S Pina António Maçanita |
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| Institution: | Centro de Tecnologia Química e Biológica, R. da Quinta Grande No. 6, 2780 Oeiras, Portugal.;Departamento de Química, Universidade Nova de Lisboa, Quinta da Torre, 2825 Monte de Caparica, Portugal.;Institute Superior Técnico, Av. Rovisco Pais, 1096 Lisboa codex, Portugal |
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| Abstract: | Abstract The excited state properties of the chalcone isomers of malvidin 3,5-diglucoside (malvin) in acidic aqueous solution (0 < pH < 4) were investigated using steady-state and time-resolved fluorescence spectroscopy. The two chalcone isomers of malvin were first isolated by high-performance liquid chromatography and then characterized by UV/visible absorption and fluorescence spectroscopy. The results were supported by molecular orbital calculations. The rate constants for photodeprotonation ( k 1= 1 × 109 s−l) and protonation ( k −1= 1.3 × 1010 L mol−1 s−l) were determined, both from the multiexponential fluorescence decays and the fluorescence intensities measured at the emission wavelengths of the neutral and ionized chalcone forms. The results here obtained are relevant for the understanding of the photoreactivity of anthocyanins in acidic medium. |
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