18393-49-2Relevant academic research and scientific papers
Analogs of anthocyanins with a 3′,4′-dihydroxy substitution: Synthesis and investigation of their acid-base, hydration, metal binding and hydrogen-donating properties in aqueous solution
Mora-Soumille, Nathalie,Al Bittar, Sheiraz,Rosa, Maxence,Dangles, Olivier
, p. 7 - 15,9 (2020/07/31)
Glycosides of hydroxylated flavylium ions are proposed as pertinent analogs of anthocyanins, a major class of polyphenolic plant pigments. Anthocyanins with a 3′,4′-dihydroxy substitution on the B-ring (catechol nucleus) are especially important for their metal chelating and electron-donating (antioxidant) capacities. In this work, an efficient chemical synthesis of 3′,4′-dihydroxy-7-O-β-d-glucopyranosyloxyflavylium chloride and its aglycone is reported. Then, the ability of the two pigments to undergo proton transfer (formation of colored quinonoid bases) and add water (formation of a colorless chalcone) is investigated: at equilibrium the colored quinonoid bases (kinetic products) are present in very minor concentrations (3+, the Al3+-glucoside complex is more stable than the Al3+-aglycone complex due to the higher sensitivity of the latter to water addition and conversion into the corresponding chalcone. Finally, the glucopyranosyloxyflavylium ion and its aglycone are compared for their ability to reduce the 1,1-diphenyl-2-picrylhydrazyl radical in a mildly acidic water/MeOH (1:1) mixture as a first evaluation of their antioxidant activity. Glycosidation at C7-OH results in a lower rate constant of first electron transfer to DPPH and a lower stoichiometry (total number of 1,1-diphenyl-2-picrylhydrazyl radicals reduced per pigment molecule). Anthocyanins are difficult to extract from plants in substantial amount. However, the analogs investigated in this work are of easy access by chemical synthesis and express the physico-chemical properties typical of anthocyanins. They can thus be regarded as valuable models for investigating the coloring, metal-binding and antioxidant properties of these important natural pigments.
30. 3′-(β-D-GlycopyranosyIoxy)flavylium Ions: Synthesis and Investigation of Their Properties in Aqueous Solution. Hydrogen Bonding as a Mean of Colour Variation
El Hajji, Hakima,Dangles, Olivier,Figueiredo, Paulo,Brouillard, Raymond
, p. 398 - 413 (2007/10/03)
This 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
Anthocyanin-aluminium and -gallium complexes in aqueous solution
Elhabiri,Figueiredo,Toki,Saito,Brouillard
, p. 355 - 362 (2007/10/03)
Complexation 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 of the pigments is demonstrated. A theoretical treatment is developed for the calculation of the corresponding stability constants. The pigments studied throughout this work can be divided into two series, one sharing a cyanidin chromophore and the other a delphinidin one. Within both series, individual pigments are distinguished according to the degree and type of glycosylation and/or acylation. Intramolecular effects such as copigmentation of anthocyanin-aluminium complexes and the effect of the presence of a malonyl group on the formation of those complexes are discussed. These results are important to plant pigmentation and, for instance, a narrow pH domain in which colour amplification due to complexation is at a maximum has been found.
