Analogs of natural 3-deoxyanthocyanins: O-glucosides of the 4′,7-dihydroxyflavylium ion and the deep influence of glycosidation on color

Nuno Basílio, Sheiraz Al Bittar, Nathalie Mora, Olivier Dangles, Fernando Pina

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

3-Deoxyanthocyanidins and their O-β-D-glucosides are natural pigments abundant in black sorghum. O-glycosidation can perturb the acid-base properties of the chromophore and lower its electron density with a large impact on the distribution of colored and colorless forms in aqueous solution. In this work, the influence of O-glycosidation on color is systematically studied from a series of 3-deoxyanthocyanin analogs. The pH- and light-dependent reversible reactions of 7-β-D-glucopyranosyloxy-4 -hydroxyflavylium (P3) and 4 -β-D-glucopyranosyloxy-7-hydroxyflavylium (P5) were completely characterized in mildly acidic solution and compared with the parent aglycone 4,7-dihydroxyflavylium ion and the O-methylethers of P3 and P5. Except P5, the chalcone forms of the pigments exhibit a high cis-trans isomerization barrier that allows a pseudo-equilibrium involving all species except the trans-chalcone. At equilibrium, only the flavylium cation and trans-chalcone are observed. With all pigments, the colored flavylium ion can be generated by irradiation of the trans-chalcone (photochromism). Glycosidation of C7–OH accelerates hydration and strongly slows down cis-trans isomerization with the pH dependence of the apparent isomerization rate constant shifting from a bell-shaped curve to a sigmoid. The color of P5 is much more stable than that of its regioisomer P3 in near-neutral conditions.

Original languageEnglish
Article number1751
JournalInternational Journal of Molecular Sciences
Volume17
Issue number10
DOIs
Publication statusPublished - Oct 2016

Keywords

  • ANTHOCYANINS
  • COMPOUNDS
  • SORGHUM
  • WATER

Fingerprint

Dive into the research topics of 'Analogs of natural 3-deoxyanthocyanins: O-glucosides of the 4′,7-dihydroxyflavylium ion and the deep influence of glycosidation on color'. Together they form a unique fingerprint.

Cite this