Antioxidant effect, DNA-binding, and transport of the flavonoid acacetin influenced by the presence of redox-active Cu(II) ion: Spectroscopic and in silico study.

Acacetin (AC) is a natural polyphenol from the group of flavonoids. It is well established that the behavior of flavonoids depends on the presence of redox-active substances; therefore, we aim to investigate their biological activity following the interaction with Cu(II) ion. Our study demonstrates that AC can effectively bind Cu(II) ions, as confirmed by UV-Vis and EPR spectroscopy as well as DFT calculations.

Revisiting Mg solubility in CuO nanorods: limit probed by neutron diffraction and effect on the particle toxicity towards bacteria in water.

Both nanometer-sized CuO and MgO particles exhibit bactericidal activities against and , two bacteria causing healthcare-associated infections. The solid solution CuMgO is potentially interesting for biomedical applications as one of the compositions could have a much higher bactericidal activity than the parent CuO and MgO oxides considered separately. But, to date, no Vegard's law proves the real existence of such a solid solution.

Understanding the bactericidal mechanism of Cu(OH) nanorods in water through Mg-substitution: high production of toxic hydroxyl radicals by non-soluble particles.

To date, there is still a lack of definite knowledge regarding the toxicity of Cu(OH) nanoparticles towards bacteria. This study was aimed at shedding light on the role played by released cupric ions in the toxicity of nanoparticles. To address this issue, the bactericidal activity of Cu(OH) was at first evaluated in sterile water, a medium in which particles are not soluble.

Azacalixphyrins as an innovative alternative for the free-radical photopolymerization under visible and NIR irradiation without the need of co-initiators.

Azacalixphyrins are unique aromatic macrocycles featuring strong absorption from the visible to the near-infrared (NIR) spectral ranges. This work demonstrates through EPR spin-trapping experiments that the -alkyl tetrasubstituted azacalixphyrin (ACP) can lead to the formation of carbon-centered radicals initiating for the free-radical photopolymerization (FRP) of bio-based acrylate monomer upon the irradiation of several light emitting diodes, which emissions range from 455 to 660 nm. Compared to other previously reported systems, the tremendous advantage of the ACP photoinitiating system is its ability to promote photopolymerization on its own, avoiding the introduction of co-initiators.

EPR Study of KO as a Source of Superoxide and BMPO-OH/OOH Radical That Cleaves Plasmid DNA and Detects Radical Interaction with HS and Se-Derivatives.

Superoxide radical anion (O) and its derivatives regulate numerous physiological and pathological processes, which are extensively studied. The aim of our work was to utilize KO as a source of O and the electron paramagnetic resonance (EPR) spin trapping 5--butoxycarbonyl-5-methyl-1-pyrroline -oxide (BMPO) technique for the preparation of BMPO-OOH and/or BMPO-OH radicals in water solution without DMSO. The method distinguishes the interactions of various compounds with BMPO-OOH and/or BMPO-OH radicals over time.

Lawsone Derivatives as Efficient Photopolymerizable Initiators for Free-Radical, Cationic Photopolymerizations, and Thiol-Ene Reactions.

Two new photopolymerizable vinyl (2-(allyloxy) 1,4-naphthoquinone, ) and epoxy (2-(oxiran-2yl methoxy) 1,4-naphthoquinone, ) photoinitiators derived from lawsone were designed in this paper. These new photoinitiators can be used as one-component photoinitiating systems for the free-radical photopolymerization of acrylate bio-based monomer without the addition of any co-initiators. As highlighted by the electron paramagnetic resonance (EPR) spin-trapping results, the formation of carbon-centered radicals from an intermolecular H abstraction reaction was evidenced and can act as initiating species.

Hydration and bactericidal activity of nanometer- and micrometer-sized particles of rock salt-type MgCuO oxides.

Copper substitution together with nano-structuring are applied with the aim to increase the bactericidal performances of the rocksalt-type MgO oxide. The partial substitution of magnesium ions with Cu has been successfully achieved in both micrometer- and nanometer-sized particles of MgO up to 20 mol% in increments of 5 mol%. Microstructural analyses using the Integral Breadth method revealed that the thermal decomposition of the single source precursor MgCu(OH)(CO).

Polyradical PROXYL/TEMPO Conjugates Connected by Ester/Amide Bridges: Synthesis, Physicochemical Studies, and DFT Calculations.

A series of di-/trinitroxide esters and amides featuring PROXYL and/or TEMPO radicals connected with alicyclic bridges were prepared in 61-92 % yields and their properties were analysed by using multiple experimental techniques. The examination of EPR spectra of radicals in organic solvents augmented with DFT calculations brought valuable information on the conformational dynamics and spin exchange mechanisms. Cyclic voltammetry investigations revealed (quasi)reversible electrochemical behaviour of studied nitroxides with their half-wave potentials ranging from -51 to -17 mV.

BMPO-OOH Spin-Adduct as a Model for Study of Decomposition of Organic Hydroperoxides and the Effects of Sulfide/Selenite Derivatives. An EPR Spin-Trapping Approach.

Lipid hydroperoxides play an important role in various pathophysiological processes. Therefore, a simple model for organic hydroperoxides could be helpful to monitor the biologic effects of endogenous and exogenous compounds. The electron paramagnetic resonance (EPR) spin-trapping technique is a useful method to study superoxide (O) and hydroxyl radicals.

Graphitic Carbon Nitride for Photocatalytic Air Treatment.

Graphitic carbon nitride (g-CN) is a conjugated polymer, which recently drew a lot of attention as a metal-free and UV and visible light responsive photocatalyst in the field of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability and earth-abundant nature. In the present work, bulk g-CN was synthesized by thermal decomposition of melamine.

Evaluation of phototoxic and cytotoxic potential of TiO2 nanosheets in a 3D reconstructed human skin model.

Despite a continuous increase of commercial products containing nanoparticles, only few materials are currently used in such large amounts, forms and sizes as titanium dioxide - TiO2. Besides its use in cosmetics, food industry and biomedicine, TiO2 nanoparticles (NPs) are also used as highly efficient photocatalysts due to their unique ability to convert complex organic materials to carbon dioxide, water and simple mineral acids via complex radical and electron transfer reactions. The main objective of the current project was to assess the potential dermal effect (phototoxicity and skin toxicity) of TiO2 nanosheets (TIG-800) synthesized from the lyophilized aqueous colloids of peroxo-titanic acid by high-temperature treatment.

Products of Sulfide/Selenite Interaction Possess Antioxidant Properties, Scavenge Superoxide-Derived Radicals, React with DNA, and Modulate Blood Pressure and Tension of Isolated Thoracic Aorta.

Selenium (Se), an essential trace element, and hydrogen sulfide (HS), an endogenously produced signalling molecule, affect many physiological and pathological processes. However, the biological effects of their mutual interaction have not yet been investigated. Herein, we have studied the biological and antioxidant effects of the products of the HS (NaS)/selenite (NaSeO) interaction.

Photoactive Polyoxometalate/DASA Covalent Hybrids for Photopolymerization in the Visible Range.

The synthesis of TBA-DASA-POM-DASA, the first photoactive covalent hybrid polyoxometalate (POM) incorporating a donor-acceptor Stenhouse adduct (DASA) reverse photochrome, is presented. It has been evidenced that in solution the equilibrium between the colorless cyclopentenone and the highly colored triene conformers is strongly dependent not only on the nature of the solvent but also the countercations, allowing to tune its optical properties. This complex has been further associated to photochromic spironaphtoxazine cations, resulting in a material which can be activated by two distinct optical stimuli.

Synthesis and Anticancer Activity of Novel 9--Substituted Berberine Derivatives.

Berberine is a bioactive isoquinoline alkaloid derived from many plants. Although berberine has been shown to inhibit growth and induce apoptosis of several tumor cell lines, its poor absorption and moderate activity hamper its full therapeutic potential. Here, we describe the synthesis of a series of 9--substituted berberine derivatives with improved antiproliferative and apoptosis-inducing activities.

Sulfide (Na₂S) and Polysulfide (Na₂S₂) Interacting with Doxycycline Produce/Scavenge Superoxide and Hydroxyl Radicals and Induce/Inhibit DNA Cleavage.

Doxycycline (DOXY) is an antibiotic routinely prescribed in human and veterinary medicine for antibacterial treatment, but it has also numerous side effects that include oxidative stress, inflammation, cancer or hypoxia-induced injury. Endogenously produced hydrogen sulfide (H₂S) and polysulfides affect similar biological processes, in which reactive oxygen species (ROS) play a role. Herein, we have studied the interaction of DOXY with H₂S (Na₂S) or polysulfides (Na₂S₂, Na₂S₃ and Na₂S₄) to gain insights into the biological effects of intermediates/products that they generate.

Copper(II) Thiosemicarbazone Complexes and Their Proligands upon UVA Irradiation: An EPR and Spectrophotometric Steady-State Study.

X- and Q-band electron paramagnetic resonance (EPR) spectroscopy was used to characterize polycrystalline Cu(II) complexes that contained sodium 5-sulfonate salicylaldehyde thiosemicarbazones possessing a hydrogen, methyl, ethyl, or phenyl substituent at the terminal nitrogen. The ability of thiosemicarbazone proligands to generate superoxide radical anions and hydroxyl radicals upon their exposure to UVA irradiation in aerated aqueous solutions was evidenced by the EPR spin trapping technique. The UVA irradiation of proligands in neutral or alkaline solutions and dimethylsulfoxide (DMSO) caused a significant decrease in the absorption bands of aldimine and phenolic chromophores.

Protective role of quercetin against copper(II)-induced oxidative stress: A spectroscopic, theoretical and DNA damage study.

The radical scavenging and metal chelating properties of flavonoids indicate that they may play a protective role in diseases with perturbed metal homeostasis such as Alzheimer's disease. In this work we investigated the effect of the coordination of quercetin to copper(II) in view of the formation of ROS in Cu-catalyzed Fenton reaction. ABTS and DPPH assays confirmed that the copper(II)-quercetin complex exhibits a stronger radical scavenging activity than does quercetin alone.

Polyradical PROXYL/TEMPO-Derived Amides: Synthesis, Physicochemical Studies, DFT Calculations, and Antimicrobial Activity.

A series of polynitroxide amides possessing 2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PROXYL) and/or 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) units connected through various bridges were synthesized and their properties were analyzed. EPR spectroscopy provided detailed insight into their paramagnetic character and related properties. A thorough examination of the EPR spectra of dinitroxides in organic solvents provided valuable information on the intramolecular motions, thermodynamics, and spin-exchange mechanisms.

Polysulfides and products of HS/S-nitrosoglutathione in comparison to HS, glutathione and antioxidant Trolox are potent scavengers of superoxide anion radical and produce hydroxyl radical by decomposition of HO.

Exogenous and endogenously produced sulfide derivatives, such as HS/HS/S, polysulfides and products of the HS/S-nitrosoglutathione interaction (S/GSNO), affect numerous biological processes in which superoxide anion (O) and hydroxyl (OH) radicals play an important role. Their cytoprotective-antioxidant and contrasting pro-oxidant-toxic effects have been reported. Therefore, the aim of our work was to contribute to resolving this apparent inconsistency by studying sulfide derivatives/free radical interactions and their consequent biological effects compared to the antioxidants glutathione (GSH) and Trolox.

Protonation and electronic structure of 2,6-dichlorophenolindophenolate during reduction. A theoretical study including explicit solvent.

Protonation in the two-electron/two-proton reduction processes of 2,6-dichlorophenolindophenolate (DCIP) is investigated combining density functional theory (DFT) and molecular dynamics (MD) methods. DCIP (anion), DCIP (radical anion), and DCIP (dianion) are considered, including the electronic structure analysis from the prospective of quantum theory of atoms and molecules (QTAIM). It is shown that oxygen on the indophenolate moiety and nitrogen are the first and/or the second proton acceptor sites and their energetic order depends on the total charge of the system.

Targeting copper(II)-induced oxidative stress and the acetylcholinesterase system in Alzheimer's disease using multifunctional tacrine-coumarin hybrid molecules.

Alzheimer's disease is a multifactorial disease that is characterized mainly by Amyloid-β (A-β) deposits, cholinergic deficit and extensive metal (copper, iron)-induced oxidative stress. In this work we present details of the synthesis, antioxidant and copper-chelating properties, DNA protection study, cholinergic activity and amyloid-antiaggregation properties of new multifunctional tacrine-7-hydroxycoumarin hybrids. The mode of interaction between copper(II) and hybrids and interestingly, the reduction of Cu(II) to Cu(I) species (for complexes Cu-5e-g) were confirmed by EPR measurements.

UVA-induced effects of 2,6-disubstituted 4-anilinoquinazolines on cancer cell lines.

Five 2,6-substituted 4-anilinoquinazolines were evaluated for their ability to generate superoxide radical anion and singlet oxygen upon UVA irradiation and to induce cytotoxic/phototoxic effects on cancer cell lines L1210, HeLa and HT-29. The formation of radical intermediates, especially reactive oxygen species, upon UVA photoexcitation of the studied derivatives was monitored by indirect techniques of EPR spectroscopy. For all 4-anilinoquinazolines the photoinduced generation of superoxide radical anion was evidenced using spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide, and the presence of (1)O2 was detected by the oxidation of 4-hydroxy-2,2,6,6-tetramethylpiperidine to the paramagnetic species 4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxyl.

The reaction products of sulfide and S-nitrosoglutathione are potent vasorelaxants.

The chemical interaction of sodium sulfide (Na2S) with the NO-donor S-nitrosoglutathione (GSNO) has been described to generate new reaction products, including polysulfides and nitrosopersulfide (SSNO(-)) via intermediacy of thionitrous acid (HSNO). The aim of the present work was to investigate the vascular effects of the longer-lived products of the Sulfide/GSNO interaction. Here we show that the products of this reaction relax precontracted isolated rings of rat thoracic aorta and mesenteric artery (but to a lesser degree rat uterus) with a >2-fold potency compared with the starting material, GSNO (50 nM), whereas Na2S and polysulfides have little effect at 1-5 µM.

Radical intermediates in photoinduced reactions on TiO2 (an EPR spin trapping study).

The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g.