Natural and Synthetic Flavylium-Based Dyes: The Chemistry Behind the Color

Abstract

Flavylium compounds are a well-known family of pigments because they are prevalent in the plant kingdom, contributing to colors over a wide range from shades of yellow-red to blue in fruits, flowers, leaves, and other plant parts. Flavylium compounds include a large variety of natural compound classes, namely, anthocyanins, 3deoxyanthocyanidins, auronidins, and their respective aglycones as well as anthocyaninderived pigments (e.g., pyranoanthocyanins, anthocyanin-flavan-3-ol dimers). During the past few decades, there has been increasing interest among chemists in synthesizing different flavylium compounds that mimic natural structures but with different substitution patterns that present a variety of spectroscopic characteristics in view of their applications in different industrial fields. This Review provides an overview of the chemistry of flavylium-based compounds, in particular, the synthetic and enzymatic approaches and mechanisms reported in the literature for obtaining different classes of pigments, their physical-chemical properties in relation to their pH-dependent equilibria network, and their chemical and enzymatic degradation. The development of flavylium-based systems is also described throughout this Review for emergent applications to explore some of the physical-chemical properties of the multistate of species generated by these compounds.

Halochromic Behavior and Anticancer Effect of New Synthetic Anthocyanidins Complexed with β-Cyclodextrin Derivatives

“…A parallel hemiketal (B) formation also occurs via nucleophilic addition of water and proton loss in a concerted process [ 37 , 38 ]. The latter form tautomerizes to cis -chalcone (Cc), which isomerizes to trans -chalcone (Ct) [ 39 , 40 ]. All these species are produced in reversible reactions.…”

“…All these species are produced in reversible reactions. Figure 5 presents the proposed pH-dependent equilibria of the synthesized anthocyanidins according to literature data [ 39 ].…”

Evaluating new blends of HFE-7100 iodine α-naphthoflavone sprays for fingermark development

“…Flavylium cations are found in natural anthocyanin pigments, wherein they generate colours ranging from red to blue/black, [16] analogous to the colouration produced by the iodinenaphthoflavone reaction. Upon subjecting a freshly mixed solution of iodine and α-naphthoflavone to electrospray mass spectrometry, six new cationic species were observed (Table 4), several consistent with iodinated adducts of α-naphthoflavone.…”

Intermolecular Copigmentation of Malvidin-3-O-glucoside with Caffeine in Water: The Effect of the Copigment on the pH-Dependent Reversible and Irreversible Processes

“… 13 − 16 Intermolecular copigmentation is used by plants to extend the pH domain of the red flavylium cation and increase the purple color of the quinoidal base. 14 The question is as follows: did intermolecular copigmentation also have some protecting effect on the anthocyanin’s degradation? From this perspective, the tools of the physical chemistry, in particular the studies concerning the pH-dependent thermodynamics and kinetics of anthocyanins, are indispensable to characterize both reversible and irreversible processes occurring in these compounds.…”

“…In eq 1 , the reaction channel occurring in the basic medium due to the OH – nucleophilic addition was added. 14 When the formation of the anionic species was not considered, the experimental data is accounted for by eq 2 . …”