Understanding the Molecular Mechanism of Anthocyanin Binding to Pectin

Association between anthocyanins and carbohydrates has drawn attention over the past few years and this interaction is of particularly importance in food chemistry since these compounds are often found together in plants and foodstuffs. This work intended to bring insights on the interaction between ionic carbohydrates (pectin) and two anthocyanins (cyanidin-3-<i>O</i>-glucoside, cy3glc and delphinidin-3-<i>O</i>-glucoside, dp3glc). The interaction between the flavylium cation and hemiketal anthocyanin forms was characterized by saturation transfer difference (STD) NMR spectroscopy and the respective dissociation constant (<i>K</i>_d) was obtained. This binding was also studied by Molecular Dynamics simulation. In the presence of the anthocyanin hemiketal form a weak interaction between anthocyanins and pectin seems to occur. A variation in the extent of this interaction was also noticed for the two anthocyanins with dp3glc bearing three hydroxyl groups, revealing to be a stronger binder to pectin (<i>K</i>_d ≈ 180 μM for dp3glc and <i>K</i>_d ≈ 250 μM for cy3glc). Experiments performed at acidic pH (flavylium cation) revealed a much stronger interaction (<i>K</i>_d ≈ 2 μM). These experimental results were also supported by theoretical studies which also revealed a stronger interaction in the presence of the anthocyanin flavylium cation and also a stronger interaction between pectin and dp3glc than with cy3glc (for the hemiketal form)

Emptying the β‑Cyclodextrin Cavity by Light: Photochemical Removal of the <i>trans</i>-Chalcone of 4′,7-Dihydroxyflavylium

The interaction between the network of chemical reactions of the compound 4′,7-dihydroxyflavylium and β-cyclodextrin was studied by means of pH jumps, followed by UV–vis absorption, flash photolysis, stopped flow, and NMR. The <i>trans</i>-chalcone is the network species exhibiting the strongest interaction with the host. In moderately acidic medium, 95% of the <i>trans</i>-chalcone, 2.5 × 10^–5 M, in the presence of β-cyclodextrin, 9 × 10^–3 M, is expected to fill the host cavity (association constant 2.2 × 10³ M^–1). In contrast, flavylium cation does not interact (association constant ≈ 0). Irradiation of the <i>trans</i>-chalcone in the presence of β-cyclodextrin 9 mM leads to the flavylium cation appearance. Light is thus capable of removing the <i>trans</i>-chalcone from the β-cyclodextrin, leaving the cavity empty. The system is reversible and <i>trans</i>-chalcone goes back to the initial state upon switching off the light due to the thermodynamic favorable conversion of flavylium cation to <i>trans</i>-chalcone in the presence of β-cyclodextrin

Impact of Lignosulfonates on the Thermodynamic and Kinetic Parameters of Malvidin-3‑<i>O</i>‑glucoside in Aqueous Solutions

The interaction of malvidin-3-<i>O</i>-glucoside (<b>1</b>) and a lignosulfonate was studied by UV–visible spectroscopy, and the results obtained showed the formation of a complex between the negatively charged lignosulfonate and the flavylium cation form (AH⁺) of this anthocyanin at pH 1. The thermodynamic and kinetic parameters of <b>1</b> in the presence of a lignosulfonate were determined by UV–visible spectroscopy and stopped-flow techniques. The main differences were observed in the flavylium cation (AH⁺)/quinoidal base (<b>A</b>) equilibrium, the AH^<b>+</b> form being more stabilized than <b>A</b> (p<i>K</i>_a1 = 4.4 ± 0.1) compared with <b>1</b> in the absence of the lignosulfonate (p<i>K</i>_a1 = 3.9 ± 0.1). Furthermore, comparing the hydration (<i>k</i>_h = 0.028 s^–1) and dehydration (<i>k</i>_–h = 40 M^–1 s^–1) processes of <b>1</b> in the presence of the lignosulfonate with the processes of <b>1</b> (<i>k</i>_h = 0.12 s^–1 and <i>k</i>_–h = 35 M^–1 s^–1) show that the hydration process is slower while the dehydration process is practically unaffected in the presence of the lignosulfonate

El Distrito Universitario : Semanario de 1ª Enseñanza: Año XVI Número 834 - 1918 agosto 2

Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 200

Cationic Half-Sandwich Iron(II) and Iron(III) Complexes with N‑Heterocyclic Carbene Ligands

The cationic piano-stool iron complexes containing the N-heterocyclic carbene ligand tethered to a tetramethylcyclopentadienyl ring [(Cp*-NHC)­Fe­(CO)­(L)]­[X] (L = NCMe, DMSO; X = BF₄, OTf) have been prepared and analyzed by spectroscopic, electrochemical, and crystallographic methods. Oxidation reactions of the cationic complex [(Cp*-NHC)­Fe­(CO)­(NCMe)]­[BF₄] (<b>2</b>) with silver tetrafluoroborate and <i>tert</i>-butyl hydroperoxide in acetonitrile yield the dicationic iron­(III) complexes [(Cp*-NHC)­Fe­(NCMe)₂]­[BF₄]₂ and [(Cp*-NHC)­Fe­(H₂O)]­[BF₄]₂, respectively. When the reaction of <b>2</b> with AgBF₄ is performed in dichloromethane, the cationic complex [(Cp*-NHC)­FeCl]­[BF₄] is obtained. These new iron­(III) complexes have been characterized by Mössbauer spectroscopy and in one case by X-ray diffraction studies. DFT calculations were used to rationalize experimental results. The cationic complex [(Cp*-NHC)­Fe­(CO)­(NCMe)]­[OTf] is catalytically active toward the reduction of benzaldehyde and acetophenone using phenylsilane under neat conditions and in the absence of visible light irradiation

Reactivity of Cork Extracts with (+)-Catechin and Malvidin-3‑<i>O</i>‑glucoside in Wine Model Solutions: Identification of a New Family of Ellagitannin-Derived Compounds (Corklins)

The aim of this study was to evaluate the reactivity of phenolic compounds extracted from cork stoppers to wine model solutions with two major wine components, namely, (+)-catechin and malvidin-3-<i>O</i>-glucoside. Besides the formation of some compounds already described in the literature, these reactions also yielded a new family of ellagitannin-derived compounds, named herein as corklins. This new family of compounds that were found to result from the interaction between ellagitannins in alcoholic solutions and (+)-catechin were structurally characterized by mass spectroscopy, nuclear magnetic resonance, and computational methods

Additional file 1: Table S1. of Studies in the mouse model identify strain variability as a major determinant of disease outcome in Leishmania infantum infection

Primers used to amplify mouse genes. (PDF 8 kb

Additional file 1: of Increased red cell distribution width in Fanconi anemia: a novel marker of stress erythropoiesis

Required informations about the unpublished data referred in the main manuscript. (PDF 463 kb