Protonation/deprotonation process of Emodin in aqueous solution and pKa determination: UV/Visible spectrophotometric titration and quantum/molecular mechanics calculations

Cunha, Antônio R. da; Duarte, Evandro L.; Lamy, M. Teresa; Coutinho, Kaline

doi:10.1016/j.chemphys.2014.06.009

Cited by 45 publications

(47 citation statements)

References 78 publications

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“…On the other hand, the anionic/deprotonated form (EM − ) is red, soluble in water and in organic solvents, and exhibits solvatochromic effects in absorption spectra. Based on quantum mechanical calculations, we previously revealed (da Cunha et al 2014) that the first deprotonation takes place at the hydroxyl substitution of carbon 3 (see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…In previous studies, UV/Visible absorption and fluorescence spectroscopy have been applied as analytical tools to study the interaction of Emodin with solvents (Pal and Jana 1993;Nguyen et al 2008;Sevilla et al 2009;da Cunha et al 2014), with biological environments like human serum albumin (HSA) (Fabriciova et al 2004;Vargas et al 2004), DNA (Wang et al 2006;Saito et al 2012;Bi et al 2008), phospholipid bilayer (Alves et al 2004) and with other environments Fig. 1 Chemical structure and atomic numbering of Emodin in its neutral form (EMH) like porous silicon (Hernandez et al 2012), silver nanoparticles (Sevilla et al 2009(Sevilla et al , 2010 and some metal ions (Pal and Jana 1993).…”

Section: Introductionmentioning

confidence: 99%

“…1 Chemical structure and atomic numbering of Emodin in its neutral form (EMH) like porous silicon (Hernandez et al 2012), silver nanoparticles (Sevilla et al 2009(Sevilla et al , 2010 and some metal ions (Pal and Jana 1993). It is known that Emodin exhibits in solution remarkable halochromic effects in absorption (Pal and Jana 1993;Nguyen et al 2008;da Cunha et al 2014) and emission spectra (Sevilla et al 2009(Sevilla et al , 2010Ghomi 2012). Thus, the first absorption band and the emission band are shifted by several tens of wavenumbers when the pH of the solution changes from acidic to alkaline.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the first absorption band and the emission band are shifted by several tens of wavenumbers when the pH of the solution changes from acidic to alkaline. In a recent work (da Cunha et al 2014), we discussed the absorption spectra of this molecule in different solvents where we showed that, in acidic aqueous solution and in common organic solvents, the main band has its maximum located around 440 nm and shows low sensitivity due to the medium. In alkaline solutions, this broad band is red-shifted, with absorption maxima, λ max , varying between 520 nm (water) and 555 nm (DMSO) depending on the solvent.…”

Section: Introductionmentioning

confidence: 99%

“…From experimental and theoretical points of view, some authors have studied the Emodin in solution by spectroscopic techniques, quantum mechanical calculations and molecular simulations elucidating many structural and electronic properties of this molecule (Pal and Jana 1993;Nguyen et al 2008;da Cunha et al 2014;Marković and Manojlović 2009). However, only one study has investigated the properties of neutral Emodin in phospholipid membranes (Alves et al 2004).…”

Section: Introductionmentioning

confidence: 99%

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Experimental and theoretical studies of emodin interacting with a lipid bilayer of DMPC

et al. 2017

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Emodin is one of the most abundant anthraquinone derivatives found in nature. It is the active principle of some traditional herbal medicines with known biological activities. In this work, we combined experimental and theoretical studies to reveal information about location, orientation, interaction and perturbing effects of Emodin on lipid bilayers, where we have taken into account the neutral form of the Emodin (EMH) and its anionic/deprotonated form (EM − ). Using both UV/Visible spectrophotometric techniques and molecular dynamics (MD) simulations, we showed that both EMH and EM − are located in a lipid membrane. Additionally, using MD simulations, we revealed that both forms of Emodin are very close to glycerol groups of the lipid molecules, with the EMH inserted more deeply into the bilayer and more disoriented relative to the normal of the membrane when compared with the EM − , which is more exposed to interfacial water. Analysis of several structural properties of acyl chains of the lipids in a hydrated pure DMPC bilayer and in the presence of Emodin revealed that both EMH and EM − affect the lipid bilayer, resulting in a remarkable disorder of the bilayer in the vicinity of the Emodin. However, the disorder caused by EMH is weaker than that caused by EM − . Our results suggest that these disorders caused by Emodin might lead to distinct effects on lipid bilayers including its disruption which are reported in the literature.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Experimental and theoretical studies of emodin interacting with a lipid bilayer of DMPC

et al. 2017

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Partition coefficients of methylated DNA bases obtained from free energy calculations with molecular electron density derived atomic charges

2018

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Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have also been used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study, atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in a vacuum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account. To test the ability of these charges to describe electrostatic interactions in force fields for condensed phases, the original atomic charges of the AMBER99 force field were replaced with the new atomic charges and combined with different solvent models to obtain the hydration and chloroform solvation free energies by molecular dynamics simulations. Chloroform-water partition coefficients derived from the obtained free energies were compared to experimental and previously reported values obtained with the GAFF or the AMBER-99 force field. The results show that good agreement with experimental data is obtained when the polarization of the electron density by the solvent has been taken into account, and when the energy needed to polarize the electron density of the solute has been considered in the transfer free energy. These results were further confirmed by hydration free energies of polar and aromatic amino acid side chain analogs. Comparison of the two partitioning methods, Hirshfeld-I and Minimal Basis Iterative Stockholder (MBIS), revealed some deficiencies in the Hirshfeld-I method related to the unstable isolated anionic nitrogen pro-atom used in the method. Hydration free energies and partitioning coefficients obtained with atomic charges from the MBIS partitioning method accounting for polarization by the implicit solvation model are in good agreement with the experimental values. © 2018 Wiley Periodicals, Inc.

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On the antibacterial photodynamic inactivation mechanism of Emodin and Dermocybin natural photosensitizers: A theoretical investigation

Ritacca,

Prejanò,

Alberto

et al. 2024

J Comput Chem

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A DFT and TDDFT study has been carried out on monomeric anthraquinones Emodin and Dermocybin (Em, Derm) recently proposed as natural antibacterial photosensitizers able to act also against gram‐negative microbes. The computational study has been performed considering the relative amount of neutral and ionic forms of each compound in water, with the variation of pH. The occurrence of both Type I and Type II photoreactions has been explored computing the absorption properties of each species, the spin‐orbit coupling constants (SOC), the vertical ionization potentials and the vertical electron affinities. The most plausible deactivation channels leading to the population of excited triplet states have been proposed. Our data indicate Emodin as more active than Dermocybin in antimicrobial photodynamic therapy throughout the Type II mechanism. Our data support a dual TypeI/II activity of the monomeric anthraquinones Emodin and Dermccybin in water, in all the considered protonation states.

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Protonation/deprotonation process of Emodin in aqueous solution and pKa determination: UV/Visible spectrophotometric titration and quantum/molecular mechanics calculations

Cited by 45 publications

References 78 publications

Experimental and theoretical studies of emodin interacting with a lipid bilayer of DMPC

Experimental and theoretical studies of emodin interacting with a lipid bilayer of DMPC

Partition coefficients of methylated DNA bases obtained from free energy calculations with molecular electron density derived atomic charges

On the antibacterial photodynamic inactivation mechanism of Emodin and Dermocybin natural photosensitizers: A theoretical investigation

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