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Impact of a Water-Soluble Gallic Acid-Based Dendrimer on the Color-Stabilizing Mechanisms of Anthocyanins
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Orientador(es)
Resumo(s)
The interaction of two anthocyanins with a water-soluble polyanionic dendrimer was studied through UV/Vis, stopped-flow, and NMR spectroscopy. Cyanidin-3-glucoside (cy3glc) revealed a stronger interaction than malvidin-3-glucoside (mv3glc) at pH 1 according to their apparent association constants. A higher color increased was also obtained for cy3glc at pH 3.5 as a result of this stronger interaction. A high-frequency chemical shift of the cy3glc aromatic protons suggest the formation of ionic pairs. The interaction parameters (K≈700 m−1, n≈295) indicated the binding of approximately two anthocyanin molecules by each sulfate group. The equilibrium and rate constants of cy3glc in the presence of dendrimer showed an increased stability of the flavylium cation and a higher protection of this species from hydration (pK′a and pKh increased almost one pH unit). The tuning and color stabilization of anthocyanins by using this dendrimer allow novel applications as colorimetric sensors for food packaging.
Descrição
project grant (PTDC/OCE-ETA/31250/2017) with financial support from FCT/MCTES through national funds and co-financed by FEDER, under the Partnership Agreement PT2020 (UID/QUI/50006/2019-POCI/01/0145/FEDER/007265). Financial support was also obtained from the Spanish Ministry of Science, Innovation and Universities (CTQ2015-69021-R and RTI2018-102212-B-I00), the Xunta de Galicia (GRC2014/040, ED431C 2018/30, and Centro Singular de Investigacion de Galicia Accreditation 2016-2019, ED431G/09) and the European Union (European Regional Development Fund-ERDF).
Palavras-chave
anthocyanins association constants gallic acid-based dendrimers NMR spectroscopy UV/Vis spectroscopy Catalysis Organic Chemistry