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Lignosulfonates are the most common commercial lignin-based product due to their unique properties. Various methods are known for modifying lignosulfonates and lignosulfonic acids. This article presents the results of the development of a new approach to the production of nitrosated lignosulfonic acids. The method is based on a reaction catalyzed by cation exchange resins in the H-form: KU-2-8 cation exchanger and wofatite. The influence of reagent consumption and reaction duration on the course of nitrosation has been studied. The dynamics of the proposed nitrosation practically coincides with the dynamics of a similar reaction using sulfuric acid by the known method. The optimal consumption of sodium nitrite equals 15 %, and the optimal consumption of cation exchanger equals 100 % by weight of lignosulfonates. During the nitrosation of lignosulfonates, significant changes in the electronic spectra occur in the region of 280...500 nm. Two overlapping absorption bands appear with maxima at 300 and 330 nm, as well as an intense absorption band at 430 nm, due to nitroso groups conjugated with the aromatic nuclei of phenylpropane units. To analyze the ionization spectra, they have been deconvoluted. The resulting spectra are well approximated by 5 Gaussians with an error of no more than 5 %. Two options for carrying out the nitrosation reaction of lignosulfonates have been proposed: under static and dynamic conditions. It has been established that under dynamic conditions, nitroso derivatives of lignosulfonic acids are formed that do not contain metal cations, and the pH of the resulting solutions does not exceed 1.4. The elemental compositions of the isolated initial and nitrosated lignosulfonic acids have been determined. The nitrogen content of lignosulfonic acids has increased from 0.32 (initial) to 2.17 % (nitrosated). In addition, under dynamic conditions, an additional stage of separating the cation exchanger from the reaction medium by filtration is not required. New bands have appeared in the IR spectrum of nitrosated lignosulfonic acids: at 1540 cm–1, which is due to the presence of nitroso groups, and a wide absorption band at 1700...1715 cm–1, which can be caused by vibrations of the carboxyl group or the quinone monooxime tautomeric form of the guaiacyl structures of lignosulfonic acids.

The nitrosation of 1H-1-alkyl-6-methyl-3-phenylpyrazolo[5,1-c][1,2,4]triazoles leads to new 1H-1-alkyl-6-methyl-7-nitroso-3-phenylpyrazolo[5,1-c][1,2,4] triazoles that react in acidic media, giving rise to 1H-1-alkyl-7-hydroxyimino-6-methyl-3-phenylpyrazolo[5,1-c][1,2,4]triazolium salts. These compounds were characterized by FT-IR, UV-Vis, 1H-NMR, 13C-NMR, and 15N-NMR spectroscopic techniques.

The human epidermal growth factor receptor (HER) family consists of four members, activated by two families of ligands. They are known for mediating cell–cell interactions in organogenesis, and their deregulation has been associated with various cancers, including breast and esophageal cancers. In particular, aberrant epidermal growth factor receptor (EGFR) and HER2 signaling drive disease progression and result in poorer patient outcomes. Nitric oxide (NO) has been proposed as an alternative activator of the HER family and may play a role in this aberrant activation due to its ability to induce s-nitrosation and phosphorylation of the EGFR. This review discusses the potential impact of NO on HER family activation and downstream signaling, along with its role in the efficacy of therapeutics targeting the family.

Cardiovascular diseases (CVDs) are often associated with impaired nitric oxide (NO) bioavailability, a critical pathophysiological alteration in CVDs and an important target for therapeutic interventions. Recent studies have revealed the potential of inorganic nitrite and nitrate as sources of NO, offering promising alternatives for managing various cardiovascular conditions. It is now becoming clear that taking advantage of enzymatic pathways involved in nitrite reduction to NO is very relevant in new therapeutics. However, recent studies have shown that nitrite may be bioactivated in the acidic gastric environment, where nitrite generates NO and a variety of S-nitrosating compounds that result in increased circulating S-nitrosothiol concentrations and S-nitrosation of tissue pharmacological targets. Moreover, transnitrosation reactions may further nitrosate other targets, resulting in improved cardiovascular function in patients with CVDs. In this review, we comprehensively address the mechanisms and relevant effects of nitrate and nitrite-stimulated gastric S-nitrosothiol formation that may promote S-nitrosation of pharmacological targets in various CVDs. Recently identified interfering factors that may inhibit these mechanisms and prevent the beneficial responses to nitrate and nitrite therapy were also taken into consideration.

Over the last two years, global regulatory authorities have raised safety concerns on nitrosamine contamination in several drug classes, including angiotensin II receptor antagonists, histamine-2 receptor antagonists, antimicrobial agents, and antidiabetic drugs. To avoid carcinogenic and mutagenic effects in patients relying on these medications, authorities have established specific guidelines in risk assessment scenarios and proposed control limits for nitrosamine impurities in pharmaceuticals. In this review, nitrosation pathways and possible root causes of nitrosamine formation in pharmaceuticals are discussed. The control limits of nitrosamine impurities in pharmaceuticals proposed by national regulatory authorities are presented. Additionally, a practical and science-based strategy for implementing the well-established control limits is notably reviewed in terms of an alternative approach for drug product N-nitrosamines without published AI information from animal carcinogenicity testing. Finally, a novel risk evaluation strategy for predicting and investigating the possible nitrosation of amine precursors and amine pharmaceuticals as powerful prevention of nitrosamine contamination is addressed.

Heme proteins are a diverse group that includes several unrelated families. Their biological function is mainly associated with the reactivity of the heme group, which—among several other reactions—can bind to and react with nitric oxide (NO) and other nitrogen compounds for their production, scavenging, and transport. The S-nitrosylation of cysteine residues, which also results from the reaction with NO and other nitrogen compounds, is a post-translational modification regulating protein activity, with direct effects on a variety of signaling pathways. Heme proteins are unique in exhibiting this dual reactivity toward NO, with reported examples of cross-reactivity between the heme and cysteine residues within the same protein. In this work, we review the literature on this interplay, with particular emphasis on heme proteins in which heme-dependent nitrosylation has been reported and those for which both heme nitrosylation and S-nitrosylation have been associated with biological functions.

Aim. To synthesize new derivatives based on hexamethylene(ethylene)-N,N’-bis(spiroindole-3,3’-pyrrolo-[3,4-c]pyrrole-2a,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trions) and 1’-(m-phenylene-N-maleimidido)-2a’,5a’-dihydro-1’H- spiroindole-3,3’-pyrrolo[3,4-c]pyrrole-2,2’,6’(1H,1’H,5’H)-trions by modifying the NH-group of the pyrrole moiety in position 4’ (alkylation, acylation, nitrosation) and study their microbiological activity. Results and discussion. The possibility of further chemical modification of the derivatives of hexamethylene(ethylene)-N,N’-bis(spiroindole-3,3’-pyrrolo[3,4-c]pyrrole-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trion) has been developed on the example of ethylene-N,N’-bis(spiroindole-3,3’-pyrrolo[3,4-c]pyrrol-5’-methyl-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trion), ethylene-N,N’-bis(spiroindole-3,3’-pyrrolo[3,4-c]pyrrole-5’-isopropyl-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trione), hexamethylene-N,N’-bis(spiroindole-3,3’-pyrrolo[3,4-c]pyrrole-5’-benzyl-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trion) and 1’-(m-phenylene-N-maleimidido)-2a’,5a’-dihydro-1’H-spiroindole-3,3’-pyrrolo[3,4-c]pyrrole-5’-methyl-2,2’,6’(1H,1’H,5’H)-trione by modification of the NH-group of the pyrrole fragment in position 4’ (nitrosation) or the NH-group of the indole fragment in position 1 (alkylation), or acylation at once in two positions. The structure of the compounds obtained has been reliably confirmed by instrumental methods. Data from the microbiological screening show a high biological effect of the compounds synthesized in relation to gram-positive (Staphylococcus aureus, Bacillus subtilis), gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris) and fungi (Candida albicans). Experimental part. The synthesis of the initial and target compounds in classical preparative conditions was performed; instrumental methods for determining the structure of organic compounds, the agar diffusion method in the modification of wells were used. Conclusions. The chemical modification of mono- and bis-derivatives of spiro-2-oxindole[3,3’]pyrrole has been performed: new functionalized nitroso derivatives have been synthesized, the alkylation reaction has been performed, and the reaction of acylation has been studied. It has been shown that the acylation occurs immediately in two positions – by the secondary amino group of the pyrrole and indole fragments, while the alkylation proceeds by the indole fragment. The structure of the compounds obtained has been proven. The antimicrobial effect of the compounds synthesized has been studied.

Increased sirtuin deacylase activity is correlated with increased lifespan and healthspan in eukaryotes. Conversely, decreased sirtuin deacylase activity is correlated with increased susceptibility to aging-related diseases. However, the mechanisms leading to decreased sirtuin activity during aging are poorly understood. Recent work has shown that oxidative post-translational modification by reactive oxygen (ROS) or nitrogen (RNS) species results in inhibition of sirtuin deacylase activity through cysteine nitrosation, glutathionylation, sulfenylation, and sulfhydration as well as tyrosine nitration. The prevalence of ROS/RNS (e.g., nitric oxide, S-nitrosoglutathione, hydrogen peroxide, oxidized glutathione, and peroxynitrite) is increased during inflammation and as a result of electron transport chain dysfunction. With age, cellular production of ROS/RNS increases; thus, cellular oxidants may serve as a causal link between loss of sirtuin activity and aging-related disease development. Therefore, the prevention of inhibitory oxidative modification may represent a novel means to increase sirtuin activity during aging. In this review, we explore the role of cellular oxidants in inhibiting individual sirtuin human isoform deacylase activity and clarify the relevance of ROS/RNS as regulatory molecules of sirtuin deacylase activity in the context of health and disease.

Proteins dynamically contribute towards maintaining cellular homeostasis. Posttranslational modification regulates the function of target proteins through their immediate activation, sudden inhibition, or permanent degradation. Among numerous protein modifications, protein nitrosation and its functional relevance have emerged. Nitrosation generally initiates nitric oxide (NO) production in association with NO synthase. NO is conjugated to free thiol in the cysteine side chain (S-nitrosylation) and is propagated via the transnitrosylation mechanism. S-nitrosylation is a signaling pathway frequently involved in physiologic regulation. NO forms peroxynitrite in excessive oxidation conditions and induces tyrosine nitration, which is quite stable and is considered irreversible. Two main reducing systems are attributed to denitrosylation: glutathione and thioredoxin (TRX). Glutathione captures NO from S-nitrosylated protein and forms S-nitrosoglutathione (GSNO). The intracellular reducing system catalyzes GSNO into GSH again. TRX can remove NO-like glutathione and break down the disulfide bridge. Although NO is usually beneficial in the basal context, cumulative stress from chronic inflammation or oxidative insult produces a large amount of NO, which induces atypical protein nitrosation. Herein, we (1) provide a brief introduction to the nitrosation and denitrosylation processes, (2) discuss nitrosation-associated human diseases, and (3) discuss a possible denitrosylation strategy and its therapeutic applications.

Non-glutinous rice boiled with adzuki bean (adzuki-meshi) is often prepared in Japan, and the colour of rice in adzuki-meshi is purplish red, suggesting the transfer of adzuki bean components to rice. In fact, red-coloured rice of adzuki-meshi contained adzuki bean flavonoids such as (+)-catechin, (−)-epicatechin, taxifolin, quercetin 7-O-glucoside, rutin, quercetin, and cyanidin-catechin conjugates (vignacyanidins). A salivary component nitrite reacted with the above flavonoids in adzuki-meshi under the conditions simulating the stomach. The reaction resulted in the decrease in the antioxidative components of adzuki-meshi, and the decrease was accompanied by the production of functional compounds like nitric oxide (•NO), 6,8-dinitrosocatechin, 6,8-dinitrosoepicatechin, and 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone from nitrous acid, (+)-catechin, (−)-epicatechin, and quercetin, respectively. In this manuscript, functions of adzuki-meshi are discussed considering the reactions of the flavonoids with nitrite in the stomach.

Protein S-nitrosation is an important consequence of NO●·metabolism with implications in physiology and pathology. The mechanisms responsible for S-nitrosation in vivo remain debatable and kinetic data on protein S-nitrosation by different agents are limited. 2-Cys peroxiredoxins, in particular Prx1 and Prx2, were detected as being S-nitrosated in multiple mammalian cells under a variety of conditions. Here, we investigated the kinetics of Prx1 S-nitrosation by nitrosoglutathione (GSNO), a recognized biological nitrosating agent, and by the dinitrosyl-iron complex of glutathione (DNIC-GS; [Fe(NO)2(GS)2]−), a hypothetical nitrosating agent. Kinetics studies following the intrinsic fluorescence of Prx1 and its mutants (C83SC173S and C52S) were complemented by product analysis; all experiments were performed at pH 7.4 and 25 ℃. The results show GSNO-mediated nitrosation of Prx1 peroxidatic residue ( k + N O C y s 52 = 15.4 ± 0.4 M−1. s−1) and of Prx1 Cys83 residue ( k + N O C y s 83 = 1.7 ± 0.4 M−1. s−1). The reaction of nitrosated Prx1 with GSH was also monitored and provided a second-order rate constant for Prx1Cys52NO denitrosation of k − N O C y s 52 = 14.4 ± 0.3 M−1. s−1. In contrast, the reaction of DNIC-GS with Prx1 did not nitrosate the enzyme but formed DNIC-Prx1 complexes. The peroxidatic Prx1 Cys was identified as the residue that more rapidly replaces the GS ligand from DNIC-GS ( k D N I C C y s 52 = 7.0 ± 0.4 M−1. s−1) to produce DNIC-Prx1 ([Fe(NO)2(GS)(Cys52-Prx1)]−). Altogether, the data showed that in addition to S-nitrosation, the Prx1 peroxidatic residue can replace the GS ligand from DNIC-GS, forming stable DNIC-Prx1, and both modifications disrupt important redox switches.

A N-nitroso moiety can be used for the activation of chloropyrimidines toward a nucleophilic substitution reaction with amines. The subsequent treatment of the obtained products with aq H2SO4 can lead to either N-denitrosation to obtain 4,6-pyrimidinediamines or to a Fischer–Hepp type rearrangement to obtain 5-nitroso-4,6-pyrimidinediamines. It was found that the outcome of the reaction strongly depends on the structure of the pyrimidines. Activation of the pyrimidine ring by three groups with a positive mesomeric effect is crucial for the intramolecular nitroso group migration.

The inhibition of nornicotine nitrosation was studied. The concentration of nornicotine was 100 μM and nitrite 1000 μM. As inhibitors were used following compounds: ascorbic acid (as reference) (800, 1000, and 5000 μM), dihydroxyfumaric acid (1000 μM), (+)catechin (1000 μM), resveratrol (1000 μM), tartaric acid (1000 μM), quercetin (1000 μM), and grape seed extract (50, 100, 150 μg/ml). The best inhibitory effect was obtained for AAs at 5000 μM (90.7%), (+)Ct (95.5 %) and GSE at 150 μg/ml (96.1%). The small inhibitory effect was observed for TA – 22,5%.

The voltage-dependent anion channel (VDAC) is the main conduit for permeation of solutes (including nucleotides and metabolites) of up to 5 kDa across the mitochondrial outer membrane (MOM). Recent studies suggest that VDAC activity is regulated via post-translational modifications (PTMs). Yet the nature and effect of these modifications is not understood. Herein, single channel currents of wild-type, nitrosated and phosphorylated VDAC are analyzed using a generalized continuous-time Markov chain Monte Carlo (MCMC) method. This developed method describes three distinct conducting states (open, half-open, and closed) of VDAC1 activity. Lipid bilayer experiments are also performed to record single VDAC activity under un-phosphorylated and phosphorylated conditions, and are analyzed using the developed stochastic search method. Experimental data show significant alteration in VDAC gating kinetics and conductance as a result of PTMs. The effect of PTMs on VDAC kinetics is captured in the parameters associated with the identified Markov model. Stationary distributions of the Markov model suggests that nitrosation of VDAC not only decreased its conductance but also significantly locked VDAC in a closed state. On the other hand, stationary distributions of the model associated with un-phosphorylated and phosphorylated VDAC suggest a reversal in channel conformation from relatively closed state to an open state. Model analyses of the nitrosated data suggest that faster reaction of nitric oxide with Cys-127 thiol group might be responsible for the biphasic effect of nitric oxide on basal VDAC conductance.

Foods are mixed with saliva in the oral cavity and swallowed. While staying in the stomach, saliva is contentiously provided to mix with the ingested foods. Because a salivary component of nitrite is protonated to produce active nitrous acid at acidic pH, the redox reactions of nitrous acid with phenolic compounds in foods become possible in the stomach. In the reactions, nitrous acid is reduced to nitric oxide (•NO), producing various products from phenolic compounds. In the products, stable hydroxybezoyl benzofuranone derivatives, which are produced from quercetin and its 7-O-glucoside, are included. Caffeic acid, chlorogenic acid, and rutin are oxidized to quinones and the quinones can react with thiocyanic acid derived from saliva, producing stable oxathiolone derivatives. 6,8-Dinitrosocatechis are produced from catechins by the redox reaction, and the dinitrocatechins are oxidized further by nitrous acid producing the quinones, which can make charge transfer complexes with the dinitrosocatechin and can react with thiocyanic acid producing the stable thiocyanate conjugates. In this way, various products can be produced by the reactions of salivary nitrite with dietary phenolic compounds, and reactive and toxic quinones formed by the reactions are postulated to be removed in the stomach by thiocyanic acid derived from saliva.

A combination of oxalic acid dihydrate and sodium nitrite in the presence of wet SiO2 was used as an effective nitrosating agent for the nitrosation of β-diketones to their corresponding α-oximinoketones in moderate to excellent yields under mild and heterogenous conditions.