Struktura hlorogenske kiseline: spektroskopski i kvantno-mehanički pristup

The aim of this work is to examine the performance of the MN12-SX method to reproduce various spectra of chlorogenic acid (5CQA). The most stable conformers of 5CQA in the gaseous and solvated states were determined. In both conformers the carboxylic hydrogen is not oriented towards the carboxylic oxygen, but towards the adjacent hydroxyl group. This occurrence is a consequence of strong, directed hydrogen bonds in the quinic moiety. MN12-SX shows excellent performance in reproducing the vibrational and NMR specra of 5CQA, but fails in simulating the UV spectrum. This shortcoming of the method can be attributed to neglecting the Hartree-Fock exchange while modeling long-range interactions.Cilj ovog rada je da se ispitaju mogućnosti metode MN12-SX da reprodukuje različite vrste spektara hlorogenske kiseline (5CQA). Određeni su najstabilniji konformeri 5CQA u gasovitoj i solvatisanoj fazi. Karakteristično za oba konformera je to da karboksilni vodoniknije okrenut ka karboksilnom kiseoniku, već ka kiseoniku susedne hidroksilne grupe, što je posledica jakih, usmerenih vodoničnih veza u hininskom delu. MN12-SX odlično reprodukuje vibracione i NMR spektre 5CQA, ali podbacuje u simuliranju UV spektra. Ova mana metode može se pripisati zanemarivanju Hartri-Fokove izmene na velikim međuatomskim rastojanjima

Examination of Electron Transfer Mechanism of Cyanidin

Cyanidin, as one important plant pigment, was theoretically (at M05-2X/6-311+G(d,p) level of theory) investigated for its ability to scavenge potentially, highly damaging hydroxyl radical. Free radical scavenging of cyanidin was studied through electron transfer mechanism – ET (the second step in SPLET mechanism) in water and ethanol, as solvents. Examination was performed using density functional theory (DFT) and Marcus theory. Based on the thermochemical and kinetic data, it is clear that O‒H group of cyanidin in position 3` is the most suitable for reaction with hydroxyl radical through mentioned antioxidant mechanism

The spectroabsorptiometric and voltammetric behavior of malvin in buffered solutions and its antioxidant properties

In the present work the structural transformations of malvin in aqueous acetate buffer solutions were investigated over a wide pH range under in vitro conditions using electronic absorption spectroscopy. In addition to the spectroabsorptiometric investigation, the voltammetric behavior and the mechanism of the redox process of this molecule were studied, in order to define its antioxidant properties. The electronic absorption spectra reveal that the structural changes of malvin, caused by changes in the pH of the medium, lead to changes in the voltammetric behaviour of this molecule. The dependence of the oxidation potential of malvin on pH, which can be explained by the presence of different electroactive molecular structures of malvin at different pH values, indicates different mechanisms of the electrode process. The voltammetric activity of malvin is compared semiquantitatively with the voltammetric activity of a standard synthetic antioxidant, BHA, and a natural antioxidant, quercetin

A spectrophotometric study of the reaction of copigmentation of malvin and tannic acid

The reaction of copigmentation of malvidin 3,5-diglucoside and tannic acid of the ester type was studied. The interactions of these molecules were observed via UV-VIS absorption spectroscopy. It was established that the pH of the medium, the concentration of the copigmentating molecules, and the temperature affect the copigmentation process. The calculated equilibrium constant of the reaction of pH 3.00 is K = 226.9, and at pH 3.65 it is K = 277.0. The change of the Gibbs free energy in pH 3.00 buffer is DG = -13.4 kJ/mol, and in pH 3.65 buffer it is DG = -13.9 kJ/mol. The stoichiometric ratio of the components in the copigment is 1:1, at both pH values. It is evident from the calculated values of the thermodynamic functions that the process is thermodynamically favorable in the lower temperature range. Temperature appears as the basic parameter of the thermodynamic feasability of the process, since the copigmentation process is exothermic (DHpH=3.00 = - 41.6 kJ/mol and DHpH=3.65 = - 41.6 kJ/mol) and proceeds with a decrease in entropy (DSpH=3.00 = - 94.4 J/mol K and DSpH=3.65 = -92.7 J/mol K)

A study of the IR spectra of the copigments of malvin chloride with organic acids

The infrared spectra of the copigments of malvin with several organic acids: caffeic, ferulic, sinapic, chlorogenic, and tannic, were analyzed in order to elucidate the bonding of the molecules in the copigments. It was established that copigmentation is realized through hydrogen bonding between malvin molecules and the acids under study. The infrared spectra reveal that two groups of hydrogen bonds are formed, which include interactions of different molecular structures: hydroxy groups (bands around 3500 cm1) and oxonium ions of the molecules (bands below 3000 cm1). The formed hydrogen bonds were found to be of different strengths. The strengths of the hydrogen bonds were tentatively correlated with thermodynamic properties of the corresponding copigmentation reactions

Le Grand écho du Nord de la France

26 juin 19051905/06/26 (A87,N177).Appartient à l’ensemble documentaire : NordPdeC

An insight into anti-biofilm and anti-quorum sensing activities of the selected anthocyanidins: the case study of <i>Pseudomonas aeruginosa</i> PAO1

<p>Anti-biofilm activity of three anthocyanidins (pelargonidin, cyanidin and delphinidin) was evaluated for the first time at <i>in vitro</i> conditions. All the compounds reduced the formation of <i>Pseudomonas aeruginosa</i> PAO1 biofilm at low sub-MIC (0.125 MIC) with delphinidin (c 56.25 μg/mL) being the most active (43%). In comparison, ampicillin (c 93.75 μg/mL) and streptomycin (c 21.25 μg/mL) (used as positive controls) were considerably less effective at the same sub-MIC (8 and 12%, respectively). Furthermore, at 0.5 MIC (c 225 μg/mL) this anthocyanidin molecule partly reduced the bacterial protrusions. However, no any of the aforementioned compounds inhibited the production of pyocyanin by the bacterial strain <i>P. aeruginosa</i> PAO1. Taken all together, the delphinidin scaffold could be taken into consideration for the design of the novel and more effective anti-biofilm agents inspired by the anthocyanidins.</p