Spectral and colorimetric characteristics of metal chelates of acylated cyanidin derivatives

Unraveling the molecular mechanisms of color expression in anthocyanins

“…3,6 This variability and complexity of color expression makes the industrial utilization of anthocyanins a challenging endeavor, compared to synthetic dyes which are more stable and predictable. Thus a deep understanding of the mechanisms of color expression in these molecules is still needed, in spite of recent extensive experimental 2,3,5,7,8 and theoretical [9][10][11][12][13][14][15][16] efforts. Moreover, most of the available studies concern the cationic species-responsible for the red hues only-while only few studies have focused so far on the neutral and negative species, which are of striking interest for industrial applications.…”

“…Moreover, most of the available studies concern the cationic species-responsible for the red hues only-while only few studies have focused so far on the neutral and negative species, which are of striking interest for industrial applications. 2,7 The color expressed by an anthocyanin solution is determined by the optical properties of the solvated molecules, which can be measured experimentally through photoabsorption spectroscopy. Predicting the color using theory and computational methods, however, is not as straightforward.…”

“…We thus aim to elucidate the relative importance of the aforementioned effects through a combination of computer simulations, performed with a newly introduced multiscale protocol that accounts for each of them at the relevant time/ length scale, and photoabsorption experiments, which have been performed for the first time systematically for a glycosylated anthocyanin over an extended (1)(2)(3)(4)(5)(6)(7)(8)(9) pH range. Our efforts are focused on cyanidin-3-O-glucoside (C3G, hereafter), chosen as a prototype for singly glycosylated anthocyanins, and which is highly abundant in nature.…”

In Vitro Bioaccessibility of Tart Cherry Anthocyanins in a Health Supplement Mix Containing Mineral Clay

“…One explanation is that metal complexing properties of anthocyanins occur with methoxyl and hydroxyl groups and the extent of chelation is dependent on pH; with lower pH having a greater effect on the metal ion to anthocyanin molar ratio than neutral pH. Metal ions will result in deprotonation of the anthocyanin B-ring, which transforms the flavylium cation to the blue quinonoidal base at low pH (Sigurdson, Robbins, Collins, & Guisti, 2017). Former studies have reported absorption peaks of malvidin-3 glucoside at visible and UV wavelengths, respectively, which were contrastingly different depending on the concentration of the metal ion present (Somaatmadja, Powers, & Hamdy, 1963).…”

The Regulation of Floral Colour Change in Pleroma raddianum (DC.) Gardner

“…Although co-pigmentation and metal complexation in this species remain to be further experimentally proven, our data allowed us to propose the formation of flavonoid–Fe 3+ complexing from S3 to S4, stabilising the pigments. Furthermore, in P. raddianum , both anthocyanins are diacyl and diglycosidic compounds, which seem to favour chelates [ 47 ]. Sigurdson et al [ 47 ] investigated colour expression and the stability of Al 3+ and Fe 3+ chelates in pH 6–7 by spectrophotometry (380–700 nm) and colorimetry (CIELab).…”