23 documents found, page 1 of 3
Photochromism of the Synthetic 4',7-Dihydroxyflavylium Chloride
Figueiredo, Paulo; Lima, João C.; Santos, Helena; Wigand, Marie Claude; Brouillard, Raymond; Maçanita, António L.; Pina, FernandoThe synthetic compound 4',7-dihydroxyflavylium chloride shows an interesting photochromic effect at moderately acidic pH values. Pale yellow solutions of this compound, equilibrated in the dark at pH 3.4, become bright yellow upon irradiation with 313-nm light. Switching off the light, gives back the initial pale yellow solution. Photochemical methods, *H NMR, and molecular orbital calculations were used to elu...
A convenient method for conversion of flavonols into anthocyanins
Elhabiri, Mourad; Figueiredo, Paulo; Fougerousse, André; Brouillard, RaymondReduction of rutin by zinc amalgam in 3% absolute methanolic hydrochloric acid provides pure 3-O-β-D-(6″′-O-α-L-(6″-deoxy-mannosyl)) glucopyranosyl-cyanidin in good yield.
New aspects of anthocyanin complexation. Intramolecular copigmentation as a mea...
Figueiredo, Paulo; Elhabiri, Mourad; Toki, Kenjiro; Saito, Nairo; Dangles, Olivier; Brouillard, RaymondTwo series of structurally related anthocyanins, extracted from the blue flowers of Evolvulus pilosus cv. Blue Daze and from the blue-purple flowers of Eichhornia crassipes, exhibit remarkable colour stabilities in aqueous solution at mildly acidic pH values. All the pigments possess the same chromophore (delphinidin), but a different pattern of glycosylation and acylation. Moreover, one of the pigments has an ...
Anthocyanin Intramolecular Interactions. A New Mathematical Approach To Account...
Figueiredo, Paulo; Elhabiri, Mourad; Saito, Norio; Brouillard, RaymondIn the last few years, a series of investigations has brought to light a mechanism of stabilization of the colorant properties of certain anthocyanins. Intramolecular interactions take place between the chromophore moiety of the anthocyanin and one of its aromatic acid residues, which folds over the chromophore and thus confers protection against hydration and subsequent formation of colorless forms. In our con...
Ground- and excited-state properties of some naphthoflavyliums
Elhabiri, Mourad; Figueiredo, Paulo; George, Florian; Cornard, Jean-Paul; Fougerousse, André; Merlin, Jean-Claude; Brouillard, RaymondA series of five, structurally related, substituted 2-phenyl-benzopyrylium (flavylium) salts were synthesized and characterized by NMR, absorption, and fluorescence techniques. Their hydration and deprotonation constants were obtained through thermodynamic and relaxation kinetic methods. Metallic complexation with the two compounds possessing a catechol group and its effect on the fluorescence intensity was als...
Anthocyanin–aluminium and –gallium complexes in aqueous solution
Elhabiri, Mourad; Figueiredo, Paulo; Toki, Kenjiro; Saito, Norio; Brouillard, RaymondComplexation of aluminium and gallium ions with synthetic anthocyanin models and natural anthocyanins extracted from the blue flowers of Evolvulus pilosus cv ‘Blue Daze’ and the violet flowers of Matthiola incana has been thoroughly investigated in aqueous solution. From UV–VIS spectroscopic data collected at pH 2–5, the presence of complexes, involving not only the coloured forms but also the colourless forms ...
3′‐(β‐D‐Glycopyranosyloxy)flavylium Ions: Synthesis and investigation of their ...
El Hajji, Hakima; Dangles, Olivier; Figueiredo, Paulo; Brouillard, RaymondThis work describes a straightforward synthesis of two 3′‐(β‐D‐glycopyranosyloxy)flavylium ions thought to be good models of natural anthocyanins (pigments). For both pigments and for the non‐glycosylated flavylium ion taken as a reference, H2O addition and proton‐transfer reactions as well as formation of molecular complexes with chlorogenic acid and caffeine (copigmentation) are quantitatively investigated in...
Malvin Z-chalcone: An unexpected new open cavity for the ferric cation
George, Florian; Figueiredo, Paulo; Brouillard, RaymondIt is demonstrated that complexation between the ferric cation and the Z-chalcone of the naturally occurring anthocyanin malvin takes place in acidic aqueous solutions. The flexible open cavity of the Z-chalcone best fits the steric and electronic requirements of the ferric ion in water.
New features of intramolecular copigmentation by acylated anthocyanins
Figueiredo, Paulo; George, Florian; Tatsuzawa, Fumi; Toki, Kenjiro; Saito, Norio; Brouillard, RaymondThree series of structurally related anthocyanins, extracted from the red–purple flowers of Dendrobium Pramot, xLaeliocattleya cv. Mini Purple, Bletilla striata and Phalaenopsis all belonging to the Orchidaceae family and another series extracted from the pink flowers of Senecio cruentus (Compositae) allowed the confirmation of the existence of strong intramolecular copigmentation effects. These interactions co...
Influence of trans-cis isomerisation of coumaric acid substituents on colour va...
George, Florian; Figueiredo, Paulo; Toki, Kenjiro; Tatsuzawa, Fumi; Saito, Norio; Brouillard, RaymondThe recently isolated pigments from Petunia integrifolia and Triteleia bridgesii present a distinct feature that sheds new light on the understanding of intramolecular copigmentation of anthocyanins. These are among the infrequent anthocyanins that naturally present a coumaric acid substituent in both cis and trans forms. As a consequence, the two isomers demonstrate substantial variations of their thermodynami...