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Title: 3’-(beta-D-Glycopyranosyloxy)flavylium Ions: Synthesis and Investigation of Their Properties in Aqueous Solution. Hydrogen Bonding as a Mean of Colour Variation
Authors: El Hajji, Hakima
Dangles, Olivier
Figueiredo, Paulo
Brouillard, Raymond
Keywords: Flavylium ions
Hydrogen bonding
Colour variation
Issue Date: 1997
Citation: HELVETICA CHIMICA ACTA- Vol. 80 398-413
Abstract: This work describes a straightforward synthesis of two 3’-(,fl-~-glycopyranosyloxy)flavyliuimo ns thought to be good models of natural anthocyanins (pigments). For both pigments and for the non-glycosylated flavylium ion taken as a reference, H,O addition and proton-transfer reactions as well as formation of molecular complexes with chlorogenic acid and caffeine (copigmentation) are quantitatively investigated in mildly acidic aqueous solution. A remarkable affinity of caffeine for the trans-chalcone form of the pigments is demonstrated. Moreover, the differences in the flavylium pK, values are interpreted in terms of possible intramolecular H-bonding between the glycosyl residue and the chromophore. The discussion is then extended to a series of malonylated anthocyanins recently reported for their unusual pigmentation properties. A possible role for the malonyl group (frequently encountered in the structure of naturally occurring anthocyanins) in plant colour expression is outlined for the first time.
Appears in Collections:A CS/CN - Artigos

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