First Characterization of the Formation of Anthocyanin–Ge and Anthocyanin–B Complexes through UV–Vis Spectroscopy and Density Functional Theory Quantum Chemical Calculations

Abstract

The occurrence of anthocyanin (ACN) and metal (Me) complexes has been widely supported by many research works while the possibility that ACNs bind to metalloids (Mds) is yet to be proven. Here, metalloids (H 3 BO 3 for B; GeO 2 for Ge) were added to cyanidin-based solutions at pH 5, 6, and 7 and ACN–Md stoichiometric ratios of 1:1, 1:10, 1:100, and 1:500, and UV–vis transmittance spectroscopy as well as density functional theory (DFT) calculations were performed to test this hypothesis. Ge and B addition caused bathochromic and hyperchromic shifts on ACN UV–vis spectra, particularly pronounced at pH 5 and a 1:500 (ACN:Md) ratio. ACN–Me complexation reactions have been evaluated where Ge showed a higher capability to bind to ACNs than B. Among the complexes envisioned, those labeled as b1 , b2 , and b3 feature UV–vis spectra compatible with experiments. The combination of experimental and computational data offers for the first time evidence of the formation of ACN–Md complexes.

Anthocyanins in photoprotection: knowing the actors in play to solve this complex ecophysiological issue

“…Finally, in vivo ‘anthocyanin spectra’ may undergo additional bathochromic shift, since anthocyanins, as well as anthocyanin–flavone copigments, form stable complexes (or supramolecular complexes in the case of copigments) with a range of metal ions (e.g. magnesium, manganese, aluminium, iron; Sigurdson & Giusti, 2014 ; Tang & Giusti, 2020 ; Estévez et al ., 2021 ), that may largely accumulate in the vacuoles of epidermal cells (Landi et al ., 2015 ). In other words, cyanic tissues have the capacity to appreciably absorb red photons too (Agati et al ., 2005 , 2007 ; Ferrandino et al ., 2017 ; Nichelmann & Bilger, 2017 ; Landi et al ., 2021 ).…”

Excited States of Six Anthocyanidin Variants with Different Solvents as Dye Sensitizers for Photocatalysis

“…Selected pigments are among the more commonly found anthocyanidins in nature, six different aglycones or anthocyanidins are included within this work and its common name with its distribution in fruits and vegetables is as follows: cyanidin 50%, pelargonidin 12%, delphinidin 12%, peonidin 12%, petunidin 7%, and malvidin 7% [15][16][17][18]. Hydroxyl and methoxy groups differentiate these molecules by the number and position of their B-ring [19][20][21].…”

Novel pH-sensitive catechol dyes synthesised by a three component one-pot reaction

“…In terms of commercial catechol dyes, either as single molecules or embedded in different materials, the most widely used in colourimetric applications are pyrocatechol violet, pyrogallol red, bromopyrogallol red and alizarin red. Some more prominent uses of these catechol dyes include their use as colourimetric sensors ( Gaidamauskas et al, 2011 ; Sasaki et al, 2019 ; Wang et al, 2020 ; Estévez et al, 2021 ; Lyu et al, 2021 ) and as pH-indicator dyes ( Ivanov, Kochelayeva, 2006 ; Lee, Lee, 2014 ; Szadkowski et al, 2022 ).…”