Role of Carbonyl Compounds for N-Nitrosamine Formation during Nitrosation: Kinetics and Mechanisms.

N-Nitrosamines are potential human carcinogens frequently detected in natural and engineered aquatic systems. This study sheds light on the role of carbonyl compounds in the formation of N-nitrosamines by nitrosation of five secondary amines via different pathways. The results showed that compared to a control system, the presence of formaldehyde enhances the formation of N-nitrosamines by a factor of 5-152 at pH 7, depending on the structure of the secondary amines. Acetaldehyde showed a slight enhancement effect on N-nitrosamine formation, while acetone and benzaldehyde did not promote nitrosation reactions. For neutral and basic conditions, the iminium ion was the dominant intermediate for N-nitrosamine formation, while carbinolamine became the major contributor under acidic conditions. Negative free energy changes (<-19 kcal mol-1) and relatively low activation energies (<18 kcal mol-1) of the reactions of secondary amines with N2O3, iminium ions with nitrite and carbinolamines with N2O3 from quantum chemical computations further support the proposed reaction pathways. This highlights the roles of the iminium ion and carbinolamine in the formation of N-nitrosamines during nitrosation in the presence of carbonyl compounds, especially in the context of industrial wastewater.

C-Nitrosation, C-Nitration, and Coupling of Flavonoids with N-Acetyltryptophan Limit This Amine N-Nitrosation in a Simulated Cured and Cooked Meat.

Nitrite is a common additive in cured meat formulation that provides microbiological safety, lipid oxidation management, and typical organoleptic properties. However, it is associated with the formation of carcinogenic N-nitrosamines. In this context, the antinitrosating capacity of selected flavonoids and ascorbate was evaluated in a simulated cooked and cured meat under formulation and digestion conditions. N-Acetyltryptophan was used as a secondary amine target. (-)-Epicatechin, rutin, and quercetin were all able to limit the formation of N-acetyl-N-nitrosotryptophan (NO-AcTrp) at pH 2.5 and pH 5 although (-)-epicatechin was 2 to 3-fold more efficient. Kinetics for the newly identified compounds allowed us to unravel common mechanistic pathways, which are flavonoid oxidation by nitrite followed by C-nitration and an original covalent coupling between NO-AcTrp and flavonoids or their nitro and nitroso counterparts. C-nitrosation of the A-ring was evidenced only for (-)-epicatechin. These major findings suggest that flavonoids could help to manage N-nitrosamine formation during cured meat processing, storage, and digestion.

Investigation of the Formaldehyde-Catalyzed NNitrosation of Dialkyl Amines: An Automated Experimental and Kinetic Modelling Study Using Dibutylamine.

The potential for drug substances and drug products to contain low levels of N-nitrosamines is of continued interest to the pharmaceutical industry and regulatory authorities. Acid-promoted nitrosation mechanisms in solution have been investigated widely in the literature and are supported by kinetic modelling studies. Carbonyl compounds, particularly formaldehyde, which may be present as impurities in excipients and drug product packaging components or introduced during drug substance manufacturing processes are also known to catalyze nitrosation, but their impact on the risk of N-nitrosamine formation has not been systematically investigated to date. In this study, we experimentally investigated the multivariate impact of formaldehyde, nitrite and pH on N-nitrosation in aqueous solution using dibutylamine as a model amine. We augmented a published kinetic model by adding formaldehyde-catalyzed nitrosation reactions. We validated the new kinetic model vs. the experimental data and then used the model to systematically investigate the impact of formaldehyde levels on N-nitrosamine formation. Simulations of aqueous solution systems show that at low formaldehyde levels the formaldehyde-catalyzed mechanisms are insignificant in comparison to other routes. However, formaldehyde-catalyzed mechanisms can become more significant at neutral and high pH under higher formaldehyde levels. Model-based sensitivity analysis demonstrated that under high nitrite levels and low formaldehyde levels (where the rate of formaldehyde-catalyzed nitrosation is low compared to the acid-promoted pathways) the model can be used with kinetic parameters for model amines in the literature without performing additional experiments to fit amine-specific parameters. For other combinations of reaction parameters containing formaldehyde, the formaldehyde-catalyzed kinetics are non-negligible, and thus it is advised that, under such conditions, additional experiments should be conducted to reliably use the model.

Morphological Effects of Au Nanoparticles on Electrochemical Sensing Platforms for Nitrite Detection.

Au nanoparticles were synthesized in a soft template of pseudo-polyanions composed of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS) by the in situ reduction of chloroauric acid (HAuCl4) with PVP. The particle sizes and morphologies of the Au nanoparticles were regulated with concentrations of PVP or SDS at room temperature. Distinguished from the Au nanoparticles with various shapes, Au nanoflowers (AuNFs) with rich protrusion on the surface were obtained at the low final concentration of SDS and PVP. The typical AuNF synthesized in the PVP (50 g·L-1)-SDS (5 mmol·L-1)-HAuCl4 (0.25 mmol·L-1) solution exhibited a face-centered cubic structure dominated by a {111} crystal plane with an average equivalent particle size of 197 nm and an average protrusion height of 19 nm. Au nanoparticles with four different shapes, nanodendritic, nanoflower, 2D nanoflower, and nanoplate, were synthesized and used to modify the bare glassy carbon electrode (GCE) to obtain Au/GCEs, which were assigned as AuND/GCE, AuNF/GCE, 2D-AuNF/GCE, and AuNP/GCE, respectively. Electrochemical sensing platforms for nitrite detection were constructed by these Au/GCEs, which presented different detection sensitivity for nitrites. The results of cyclic voltammetry (CV) demonstrated that the AuNF/GCE exhibited the best detection sensitivity for nitrites, and the surface area of the AuNF/GCE was 1.838 times of the bare GCE, providing a linear c(NO2-) detection range of 0.01-5.00 µmol·L-1 with a limit of detection of 0.01 µmol·L-1. In addition, the AuNF/GCE exhibited good reproducibility, stability, and high anti-interference, providing potential for application in electrochemical sensing platforms.

Self-supported polypyrrole flexible electrodes for electrochemical reduction of nitrite.

The efficiency of an electrochemical oxidation/reduction process strongly depends on the working electrode's surface area to volume ratio. By making electrodes flexible and employing different configurations such as roll-to-roll membrane, the surface area to volume ratio can be enhanced, therefore improving the overall efficiency of electrochemical processes. Conductive polymers emerge as a new framework to enable alternative electrochemical water treatment cell configurations. Self-standing polypyrrole flexible electrodes were synthesized by electropolymerization and evaluated on the treatment of an oxyanion pollutant: nitrite. Mechanical characterization through stress-strain curves and bending tests demonstrated high electrode resilience that sustained over 1000 bending cycles without impacting mechanical integrity or electrocatalytic responses. The electrocatalytic response towards nitrite reduction was assessed under linear scan voltammetry (LSV) and removal performance evaluated under potentiostatic conditions reaching 79% abatement of initial concentrations of nitrite of 15 mg/L [NO2--N]. Self-standing flexible electrodes appear as a novel framework to enable modular compact water treatment unit designs that maximize the electrode area/volume ratio and substitute expensive platinum group metal (PGMs) electrocatalysts.

GC-MS Studies on Nitric Oxide Autoxidation and S-Nitrosothiol Hydrolysis to Nitrite in pH-Neutral Aqueous Buffers: Definite Results Using 15N and 18O Isotopes.

Nitrite (O=N-O-, NO2-) and nitrate (O=N(O)-O-, NO3-) are ubiquitous in nature. In aerated aqueous solutions, nitrite is considered the major autoxidation product of nitric oxide (●NO). ●NO is an environmental gas but is also endogenously produced from the amino acid L-arginine by the catalytic action of ●NO synthases. It is considered that the autoxidation of ●NO in aqueous solutions and in O2-containing gas phase proceeds via different neutral (e.g., O=N-O-N=O) and radical (e.g., ONOO●) intermediates. In aqueous buffers, endogenous S-nitrosothiols (thionitrites, RSNO) from thiols (RSH) such as L-cysteine (i.e., S-nitroso-L-cysteine, CysSNO) and cysteine-containing peptides such as glutathione (GSH) (i.e., S-nitrosoglutathione, GSNO) may be formed during the autoxidation of ●NO in the presence of thiols and dioxygen (e.g., GSH + O=N-O-N=O → GSNO + O=N-O- + H+; pKaHONO, 3.24). The reaction products of thionitrites in aerated aqueous solutions may be different from those of ●NO. This work describes in vitro GC-MS studies on the reactions of unlabeled (14NO2-) and labeled nitrite (15NO2-) and RSNO (RS15NO, RS15N18O) performed in pH-neutral aqueous buffers of phosphate or tris(hydroxyethylamine) prepared in unlabeled (H216O) or labeled H2O (H218O). Unlabeled and stable-isotope-labeled nitrite and nitrate species were measured by gas chromatography-mass spectrometry (GC-MS) after derivatization with pentafluorobenzyl bromide and negative-ion chemical ionization. The study provides strong indication for the formation of O=N-O-N=O as an intermediate of ●NO autoxidation in pH-neutral aqueous buffers. In high molar excess, HgCl2 accelerates and increases RSNO hydrolysis to nitrite, thereby incorporating 18O from H218O into the SNO group. In aqueous buffers prepared in H218O, synthetic peroxynitrite (ONOO-) decomposes to nitrite without 18O incorporation, indicating water-independent decomposition of peroxynitrite to nitrite. Use of RS15NO and H218O in combination with GC-MS allows generation of definite results and elucidation of reaction mechanisms of oxidation of ●NO and hydrolysis of RSNO.

Catalytic degradation of "trinitrogen" by Fe-Ce-SiO2 /TiO2 aerogel.

The "trinitrogen" [ammonia nitrogen (NH4+ - N), nitrate nitrogen (NO3- - N), and nitrite nitrogen (NO2- - N)] from industrial or domestic wastewater can lead to eutrophication of water bodies. When ammonia nitrogen is converted into nitrate nitrogen, it will cause high nitrogen oxygen demand, which will also lead to hyperammonemia. High nitrite content in water bodies will increase the risk of human cancer. In this paper, Fe-Ce bimetallic-doped composites (Fe-Ce/SiO2 and Fe-Ce-SiO2/TiO2) were synthesized using SiO2 aerogel as a carrier for the adsorption and degradation of "three nitrogen."SiO2/TiO2 was prepared by dipping method, and Fe and Ce bimetals were loaded on the surface of SiO2/TiO2 material, and the effect of photo-Fenton oxidation on the degradation rate of three nitrogen under different materials was explored. The results showed that when the dosage of catalyst was 0.01 g, pH value was 11.0, and the concentration of H2O2 was 80 mmol/L, the photocatalytic efficiency was the best, and the degradation efficiency of three nitrogen remained above 70%.

A Model Assessment of the Occurrence and Reactivity of the Nitrating/Nitrosating Agent Nitrogen Dioxide (•NO2) in Sunlit Natural Waters.

Nitrogen dioxide (•NO2) is produced in sunlit natural surface waters by the direct photolysis of nitrate, together with •OH, and upon the oxidation of nitrite by •OH itself. •NO2 is mainly scavenged by dissolved organic matter, and here, it is shown that •NO2 levels in sunlit surface waters are enhanced by high concentrations of nitrate and nitrite, and depressed by high values of the dissolved organic carbon. The dimer of nitrogen dioxide (N2O4) is also formed in the pathway of •NO2 hydrolysis, but with a very low concentration, i.e., several orders of magnitude below •NO2, and even below •OH. Therefore, at most, N2O4 would only be involved in the transformation (nitration/nitrosation) of electron-poor compounds, which would not react with •NO2. Although it is known that nitrite oxidation by CO3•- in high-alkalinity surface waters gives a minor-to-negligible contribution to •NO2 formation, it is shown here that NO2- oxidation by Br2•- can be a significant source of •NO2 in saline waters (saltwater, brackish waters, seawater, and brines), which offsets the scavenging of •OH by bromide. As an example, the anti-oxidant tripeptide glutathione undergoes nitrosation by •NO2 preferentially in saltwater, thanks to the inhibition of the degradation of glutathione itself by •OH, which is scavenged by bromide in saltwater. The enhancement of •NO2 reactions in saltwater could explain the literature findings, that several phenolic nitroderivatives are formed in shallow (i.e., thoroughly sunlit) and brackish lagoons in the Rhône river delta (S. France), and that the laboratory irradiation of phenol-spiked seawater yields nitrophenols in a significant amount.

Electrochemical Sensor Based on Iron(II) Phthalocyanine and Gold Nanoparticles for Nitrite Detection in Meat Products.

Nitrites are widely used in the food industry, particularly for the preservation of meat products. Controlling the nitrate content in food is an important task to ensure people's health is not at risk; therefore, the search for, and research of, new materials that will modify the electrodes in the electrochemical sensors that detect and control the nitrate content in food products is an urgent task. In this paper, we describe the electrochemical behavior of a glass carbon electrode (GCE), modified with a Fe(II) tetra-tert-butyl phthalocyanine film (FePc(tBu)4/GCE), and decorated with gold nanoparticles (Au/FePc(tBu)4/GCE); this electrode was deposited using gas-phase methods. The composition and morphology of such electrodes were examined using spectroscopy and electron microscopy methods, whereas the main electrochemical characteristics were determined using cyclic voltammetry (CV) and amperometry (CA) methods in the linear ranges of CV 0.25-2.5 mM, CA 2-120 µM in 0.1 M phosphate buffer (pH = 6.8). The results showed that the modification of bare GCEs, with a Au/FePc(tBu)4 heterostructure, provided a high surface-to-volume ratio, thus ensuring its high sensitivity to nitrite ions of 0.46 µAµM-1. The sensor based on the Au/FePc(tBu)4/GCE has a low limit of nitrite detection at 0.35 µM, good repeatability, and stability. The interference study showed that the proposed Au/FePc(tBu)4/GCE exhibited a selective response in the presence of interfering anions, and the analytical capability of the sensor was demonstrated by determining nitrite ions in real samples of meat products.

Reaction mechanisms relevant to the formation and utilization of [Ru(edta)(NO)] complexes in aqueous media.

The advancement of Ru(edta) complexes (edta4- = ethylenediamineteraacetate) mediated reactions, including NO generation and its utilization, has not been systematically reviewed to date. This review aims to report the research progress that has been made in exploring the application of Ru(edta) complexes in trapping and generation of NO. Furthermore, utilization of the potential of Ru(edta) complexes to mimic NO synthase and nitrite reductase activity, including thermodynamics and kinetics of NO binding to Ru(edta) complexes, their NO scavenging (in vitro), and antitumor activity will be discussed. Also, the role of [Ru(edta)(NO)] in mediating electrochemical reduction of nitrite, S-nitrosylation of biological thiols, and cross-talk between NO and H2S, will be covered. Reports on the NO-related chemistry of Fe(edta) complexes showing similar behavior are contextualized in this review for comparison purposes. The research contributions compiled herein will provide in-depth mechanistic knowledge for understanding the diverse routes pertaining to the formation of the [Ru(edta)(NO)] species, and its role in effecting the aforementioned reactions of biochemical significance.

Nitrite as a causal factor for nitrate-dependent anaerobic corrosion of metallic iron induced by Prolixibacter strains.

Microbially influenced corrosion (MIC) may contribute significantly to overall corrosion risks, especially in the gas and petroleum industries. In this study, we isolated four Prolixibacter strains, which belong to the phylum Bacteroidetes, and examined their nitrate respiration- and Fe0 -corroding activities, together with two previously isolated Prolixibacter strains. Four of the six Prolixibacter strains reduced nitrate under anaerobic conditions, while the other two strains did not. The anaerobic growth of the four nitrate-reducing strains was enhanced by nitrate, which was not observed in the two strains unable to reduce nitrate. When the nitrate-reducing strains were grown anaerobically in the presence of Fe0 or carbon steel, the corrosion of the materials was enhanced by more than 20-fold compared to that in aseptic controls. This enhancement was not observed in cultures of the strains unable to reduce nitrate. The oxidation of Fe0 in the anaerobic cultures of nitrate-reducing strains occurred concomitantly with the formation of nitrite. Since nitrite chemically oxidized Fe0 under anaerobic and aseptic conditions, the corrosion of Fe0 - and carbon steel by the nitrate-reducing Prolixibacter strains was deduced to be mainly enhanced via the biological reduction of nitrate to nitrite, followed by the chemical oxidation of Fe0 to Fe2+ and Fe3+ coupled to the reduction of nitrite.

Design, Synthesis, and Biological Evaluation of Organic Nitrite (NO2-) Donors as Potential Anticerebral Ischemia Agents.

The treatment of ischemic stroke (IS) remains a big challenge in clinics, and it is urgently needed to develop novel, safe, and effective medicines against IS. Here, we report the design, synthesis, and biological evaluation of organic NO2- donors as potential agents for the treatment of IS. The representative compound 4a was able to slowly generate low concentrations of NO2- by reaction with a thiol-containing nucleophile, and the NO2- was selectively converted into NO under ischemic/hypoxia conditions to protect primary rat neurons from oxygen-glucose deprivation and recovery (OGD/R)-induced cytotoxicity by enhancing the Nrf2 signaling and activating the NO/cGMP/PKG pathway. Treatment with 4a at 2 h before or after ischemia mitigated the ischemia/reperfusion-induced brain injury in middle cerebral artery occlusion (MCAO) rats by producing NO and enhancing Nrf2 signaling. Furthermore, 4a significantly promoted endothelial cell proliferation and angiogenesis within the ischemic penumbra. Our findings suggest that this type of NO2- donors, like 4a, may be valuable to fight IS and other ischemic diseases.

The Quest to Quantify Selective and Synergistic Effects of Plasma for Cancer Treatment: Insights from Mathematical Modeling.

Cold atmospheric plasma (CAP) and plasma-treated liquids (PTLs) have recently become a promising option for cancer treatment, but the underlying mechanisms of the anti-cancer effect are still to a large extent unknown. Although hydrogen peroxide (H2O2) has been recognized as the major anti-cancer agent of PTL and may enable selectivity in a certain concentration regime, the co-existence of nitrite can create a synergistic effect. We develop a mathematical model to describe the key species and features of the cellular response toward PTL. From the numerical solutions, we define a number of dependent variables, which represent feasible measures to quantify cell susceptibility in terms of the H2O2 membrane diffusion rate constant and the intracellular catalase concentration. For each of these dependent variables, we investigate the regimes of selective versus non-selective, and of synergistic versus non-synergistic effect to evaluate their potential role as a measure of cell susceptibility. Our results suggest that the maximal intracellular H2O2 concentration, which in the selective regime is almost four times greater for the most susceptible cells compared to the most resistant cells, could be used to quantify the cell susceptibility toward exogenous H2O2. We believe our theoretical approach brings novelty to the field of plasma oncology, and more broadly, to the field of redox biology, by proposing new ways to quantify the selective and synergistic anti-cancer effect of PTL in terms of inherent cell features.

Reusable 3D silver superposed silica SERS substrate based on the Griess reaction for the ratiometric detection of nitrite.

When nitrite is ingested and absorbed by the body, it can be converted into highly toxic nitrosamines (carcinogens, teratogens, and mutagens), posing health risks to the general population. Therefore, it calls for establishing a method for determination of nitrite. In this paper, the glass-SiO2-Ag surface-enhanced Raman scattering (SERS) substrate with a large number of "hot spots" were prepared by two kinds of silane coupling agents. The SERS substrate had high sensitivity and repeatability. Silicon dioxide supported the silver nanoparticles (Ag NPs), which increased surface roughness of the substrate, generated a great quantity of hot spots and enhanced the SERS signal. In the SERS spectrum, the intensity ratio of the two characteristic peaks (1287 cm-1 and 1076 cm-1) had a good linear correlation with the logarithm of the concentration of nitrite, R2 = 0.9652. The recoveries of 50 µM and 100 µM nitrite in three kinds of foods, three kinds of cosmetics and tap water were 90.9-105.3%.

Investigating the root cause of N-nitrosodimethylamine formation in metformin pharmaceutical products.

BACKGROUND: FDA limited N-nitrosodimethylamine (NDMA) - a carcinogenic impurity formed during metformin (MET) tablets manufacturing - level to 96 ng/day; a step which led to recall of MET products. This work aims to investigate the root cause of NDMA formation during MET tablets manufacturing. RESEARCH DESIGN AND METHODS: We focused on three main contributing causes: use of water and heat during intra-granulation, and the nitrite/nitrate quantities in excipients. Thirteen MET tablet formulations (immediate or sustained-release) were manufactured, on batch level. Each batch was manufactured using one excipient and excluding one cause at a time and NDMA level was assayed. RESULTS: NDMA traces were undetectable in MET tablets manufactured using polyvinyl pyrrolidone or hydroxypropyl cellulose SSL, even when water and/or heat were employed during intra-granulation. Levels of NDMA in MET tablets with hydroxypropyl methyl cellulose (HPMC) E5 or carboxymethyl cellulose sodium 4000 were 67.08 ± 2.3 and 66.21 ± 2.5 ng/day, in the presence of water and/or heat. No impact of employing extra-granular PolyoxTM, HPMC E5 or HPMC K15 on NDMA formation, despite the high nitrite and nitrate content in these excipients. CONCLUSIONS: Water, heat, and excipients' nitrite and nitrate levels are the key players, which should collectively exist, to cause NDMA formation during MET tablets manufacturing.

Nitrite-Responsive Hydrogel: Smart Drug Release Depending on the Severity of the Nitric Oxide-Related Disease.

Nitric oxide (NO) is known as one of the most important biomarkers of many diseases. However, the development of NO-triggered drug releasing platforms is challenging due to the low concentration and short lifetime of NO in vivo. In this work, a novel nitrite (NO2-)-responsive hydrogel (DHPL-GEL), which can be used for smart drug release depending on the severity of the NO-related disease, is demonstrated. A dihydropyridine cross-linking agent is designed to construct DHPL-GEL to enable the responsive degradation of the hydrogel triggered by NO2-. On-demand release of the drug loaded in DHPL-GEL was observed under the stimulation of various concentrations of NO2- at the physiological level both in vitro and in vivo. In the inflammatory arthritis rat model, the DHPL-GEL drug delivery system showed a better therapeutic effect and less side effects than the traditional therapy and nonresponsive hydrogel drug delivery system, demonstrating the promising application of the NO2--responsive hydrogel for the treatment of NO-related diseases.

Temperature-Dependent Formation of N-Nitrosodimethylamine during the Storage of Ranitidine Reagent Powders and Tablets.

The purpose of this study was to elucidate the effect of high-temperature storage on the stability of ranitidine, specifically with respect to the potential formation of N-nitrosodimethylamine (NDMA), which is classified as a probable human carcinogen. Commercially available ranitidine reagent powders and formulations were stored under various conditions, and subjected to LC-MS/MS analysis. When ranitidine tablets from two different brands (designated as tablet A and tablet B) were stored under accelerated condition (40 °C with 75% relative humidity), following the drug stability guidelines issued by the International Conference on Harmonisation (ICH-Q1A), for up to 8 weeks, the amount of NDMA in them substantially increased from 0.19 to 116 ppm and from 2.89 to 18 ppm, respectively. The formation of NDMA that exceeded the acceptable daily intake limit (0.32 ppm) at the temperature used under accelerated storage conditions clearly highlights the risk of NDMA formation in ranitidine formulations when extrapolated to storage under ambient conditions. A forced-degradation study under the stress condition (60 °C for 1 week) strongly suggested that environmental factors such as moisture and oxygen are involved in the formation of NDMA in ranitidine formulations. Storage of ranitidine tablets and reagent powders at the high temperatures also increased the amount of nitrite, which is considered one of the factors influencing NDMA formation. These data indicate the necessity of controlling/monitoring stability-related factors, in addition to controlling impurities during the manufacturing process, in order to mitigate nitrosamine-related health risks of certain pharmaceuticals.

Dinitrosyliron Complex [(PMDTA)Fe(NO)2]: Intermediate for Nitric Oxide Monooxygenation Activity in Nonheme Iron Complex.

Despite a comprehensive study on the biosynthesis and function of nitric oxide, biological metabolism of nitric oxide, especially when its concentration exceeds the cytotoxic level, remains elusive. Oxidation of nitric oxide by O2 in aqueous solution has been known to yield NO2-. On the other hand, a biomimetic study on the metal-mediated conversion of NO to NO2-/NO3- via O2 reactivity disclosed a conceivable pathway for aerobic metabolism of NO. During the NO-to-NO3- conversion, transient formation of metal-bound peroxynitrite and subsequent release of •NO2 via O-O bond cleavage were evidenced by nitration of tyrosine residue or 2,4-di-tert-butylphenol (DTBP). However, the synthetic/catalytic/enzymatic cycle for conversion of nitric oxide into a nitrite pool is not reported. In this study, sequential reaction of the ferrous complex [(PMDTA)Fe(κ2-O,O'-NO2)(κ1-O-NO2)] (3; PMDTA = pentamethyldiethylenetriamine) with NO(g), KC8, and O2 established a synthetic cycle, complex 3 → {Fe(NO)2}9 DNIC [(PMDTA)Fe(NO)2][NO2] (4) → {Fe(NO)2}10 DNIC [(PMDTA)Fe(NO)2] (1) → [(PMDTA)(NO)Fe(κ2-O,N-ONOO)] (2) → complex 3, for the transformation of nitric oxide into nitrite. In contrast to the reported reactivity of metal-bound peroxynitrite toward nitration of DTBP, peroxynitrite-bound MNIC 2 lacks phenol nitration reactivity toward DTBP. Presumably, the [(PMDTA)Fe] core in {Fe(NO)}8 MNIC 2 provides a mononuclear template for intramolecular interaction between Fe-bound peroxynitrite and Fe-bound NO-, yielding Fe-bound nitrite stabilized in the form of complex 3. This [(PMDTA)Fe]-core-mediated concerted peroxynitrite homolytic O-O bond cleavage and combination of the O atom with Fe-bound NO- reveals a novel and effective pathway for NO-to-NO2- transformation. Regarding the reported assembly of the dinitrosyliron unit (DNIU) [Fe(NO)2] in the biological system, this synthetic cycle highlights DNIU as a potential intermediate for nitric oxide monooxygenation activity in a nonheme iron system.

Systemic Administration of Calea pinnatifida Inhibits Inflammation Induced by Carrageenan in a Murine Model of Pulmonary Neutrophilia.

OBJECTIVE: The aim of this study was to investigate the anti-inflammatory effects of the crude extract (CE), derived fraction, and isolated compounds from Calea pinnatifida leaves in a mouse model of pulmonary neutrophilia. METHODS: The CE and derived fractions, hexane, ethyl acetate, and methanol, were obtained from C. pinnatifida leaves. The compounds 3,5- and 4,5-di-O-E-caffeoylquinic acids were isolated from the EtOAc fraction using chromatography and were identified using infrared spectroscopic data and nuclear magnetic resonance (1H and 13C NMR). Leukocytes count, protein concentration of the exudate, myeloperoxidase (MPO) and adenosine deaminase (ADA), and nitrate/nitrite (NO x ), tumor necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1ß), and interleukin-17A (IL-17A) levels were determined in the pleural fluid leakage after 4 h of pleurisy induction. We also analyzed the effects of isolated compounds on the phosphorylation of both p65 and p38 in the lung tissue. RESULTS: The CE, its fractions, and isolated compounds inhibited leukocyte activation, protein concentration of the exudate, and MPO, ADA, NO x , TNF-α, IL-1ß, and IL-17A levels. 3,5- and 4,5-di-O-E-caffeoylquinic acids also inhibited phosphorylation of both p65 and p38 (P < 0.05). CONCLUSION: This study demonstrated that C. pinnatifida presents important anti-inflammatory properties by inhibiting activated leukocytes and protein concentration of the exudate. These effects were related to the inhibition of proinflammatory mediators. The dicaffeoylquinic acids may be partially responsible for these anti-inflammatory properties through the inhibition of nuclear transcription factor kappa B and mitogen-activated protein kinase pathways.

A Design of Experiments Strategy to Enhance the Recovery of Polyphenolic Compounds from Vitis vinifera By-Products through Heat Reflux Extraction.

The aim of the present study was to establish the best experimental conditions that lead to the extracts richest in polyphenolic compounds obtained from pomace and canes of Vitis vinifera. In this regard, a D-Optimal design of experiments (DoE) method was applied to investigate the extraction process parameters from each of three materials: red pomace (RP), white pomace (WP) and canes (C). The input variables were the extraction temperature and the ethanol ratio and as response, the total polyphenols content (TPC) was determined. A design space was generated for each of the plant materials and the most concentrated polyphenol extracts were obtained using 50% ethanol at a temperature of 80 °C. Further, the phenolic profiles of the concentrated extracts were detected by LC/MS/MS and the results showed that WP extract was richer in polyphenolic compounds, both flavonoid and phenolic acids, followed by the RP and C extracts. The antioxidant assays revealed that WP and RP extracts exhibited a higher antioxidant activity which correlated to the high content of polyphenols. These findings revealed that RP, WP and C, currently considered agricultural wastes from winery, may be valorized as an important source of natural antioxidants.