Search Results (152)

N,N-Ditosyl-2-aminodiphenylamine was prepared by the tosylation of 2-aminodiphenylamine with tosylchloride in dichloromethane. Unwanted isomers owing to the tosylation of the diarylamine were not formed. This compound was fully characterized by IR, UV/Vis, NMR, m/z, and mp, including an X-Ray single crystal structure determination. It was fragmented in an Atmospheric Solids Analysis Probe (ASAP) mass spectrometer showing a series of fragments down to phenazine. Full article

Pseudomonas aeruginosa is an opportunistic pathogen capable of forming antibiotic-resistant biofilms, contributing to persistent infections and treatment failure. Environmental factors such as osmolarity and nutrient availability are known to influence biofilm formation and virulence. In this study, we investigated the effects of NaCl depletion and glutamine supplementation on biofilm production in three P. aeruginosa strains: the laboratory strain ATCC 27853 and two clinical isolates with distinct antibiotic resistance profiles and phenazine production patterns (P. aeruginosa Pr, pyorubrin-producing, and P. aeruginosa Pc, pyocyanin-producing). Bacteria were cultured in standard Luria–Bertani (LB) medium, LB without NaCl, and LB in which yeast extract was replaced by glutamine. For each strain and condition, we assessed growth kinetics, phenazine production, and biofilm formation. Biofilm development was quantified via XTT assays and compared to secondary metabolite profiles. NaCl removal did not substantially affect growth, whereas glutamine supplementation reduced growth, especially in the laboratory strain. Both conditions modulated secondary metabolite production and biofilm formation in a strain-specific manner. In P. aeruginosa ATCC 27853, NaCl depletion significantly increased pyoverdine, pyocyanin, and QS gene expression, while biofilm formation showed significant differences only at 72 h; in contrast, glutamine supplementation affected only pyoverdine. A similar trend was observed in the clinical strain P. aeruginosa Pc, although NaCl depletion did not significantly impact pyoverdine production but already enhanced biofilm formation at 48 h. In P. aeruginosa Pr, only glutamine appeared to alter the considered parameters, increasing pyoverdine production while reducing pyocyanin and biofilm levels, although the absence of NaCl also negatively impacted biofilm formation. These findings highlight the impact of osmotic and nutritional signals on P. aeruginosa virulence traits. Full article

The [2Fe-2S] transcription activator SoxR, a member of the MerR family, functions as a bacterial stress response sensor. The response governed by SoxR is activated by the oxidation of the [2Fe-2S]. In this review, I describe functional differences between Escherichia coli SoxR (EcSoxR) and Pseudomonas aeruginosa SoxR (PaSoxR). Pulse radiolysis demonstrated that the reduced form of EcSoxR reacts directly with O₂⁻ with a second-order rate constant of 5.0 × 10⁸ M⁻¹s⁻¹. PaSoxR was found to undergo a similar reaction, although with a 10-fold smaller rate constant (4.0 × 10⁷ M⁻¹s⁻¹). This difference in rate constants may reflect distinct regulatory features of EcSoxR and PaSoxR. Specifically, mutagenesis studies have shown that Lysine residues―which are located close to [2Fe-2S] clusters, in EcSoxR, but are not conserved in PaSoxR―are essential for EcSoxR activation. In contrast, both EcSoxR and PaSoxR were found to react with various redox-active compounds (RACs), including viologens, phenazines, and quinones, with no apparent differences in the kinetic behavior or specificity of the two proteins. Importantly, both O₂⁻ and RACs oxidize SoxR with the same rate constants. soxR regulon may be induced through multiple pathways, and the activation may depend on the cellular concentration of O₂⁻ and RACs. Full article

The synthesis of heterocyclic compounds has gained significant attention in organic chemistry due to their diverse pharmacological properties. However, traditional synthetic approaches often involve hazardous chemicals, high energy consumption, and tedious workup procedures, leading to environmental concerns and low yields. In response, green chemistry strategies have emerged, emphasizing safer and more sustainable alternatives. Among these, magnetic nanoparticle (MNP)-based catalysts have shown remarkable promise in facilitating one-pot multicomponent reactions (MCRs), offering enhanced catalytic efficiency, ease of recovery, and reusability. This article provides a comprehensive overview of multicomponent reactions (MCRs) for the construction of a wide range of heterocyclic scaffolds—including chromenes, pyrazoles, phenazines, triazoles, tetrazoles, xanthenes, furans, indoles, imidazoles, pyridines, pyrimidines, oxazoles, and acridine derivatives—catalyzed by magnetic nanoparticles under sustainable and environmentally benign conditions. This review highlights recent advances (2018–2024) in the development and application of modified magnetic nanoparticles for green multicomponent synthesis. Emphasis is placed on their structural features, catalytic roles, and benefits in eco-friendly organic transformations. Full article

Covalent triazine frameworks (CTFs) have gained recognition as stable porous organic polymers, for example, for CO₂ separation. From the monomer 4,4′-(phenazine-5,10-diyl)dibenzonitrile (pBN), new pBN-CTFs were synthesized using the ionothermal method with a variation in temperature (400 and 550 °C) and the ZnCl₂-to-monomer ratio (10 and 20). N₂ adsorption yielded BET surface areas up to 1460 m²g ⁻¹. The pBN-CTFs are promising CO₂ adsorbents and are comparable to other benchmark CTFs such as CTF-1 with a CO₂ uptake of pBN-CTF-10-550 at 293 K of up to 54 cm³ g⁻¹ or 96 mg g⁻¹, with a CO₂/CH₄ IAST selectivity of 22 for a 50% mixture of CO₂/CH₄. pBN-CTF-10-400 has a very high heat of adsorption of 79 kJ mol⁻¹ for CO₂ near zero coverage in comparison to other CTFs, and it also stays well above the liquefaction heat of CO₂ due to its high microporosity of 50% of the total pore volume. Full article

Boronic acids are an important class of molecules diversely used in organic synthesis, catalysis, medicinal chemistry, and for the design of functional materials. Particularly, aryl boronic acids in the solid state are known to exhibit pharmaceutical and photoluminescent properties for antimicrobial, sensing, and drug delivery applications. Furthermore, the phenazine molecule is known for its diverse pharmacological properties, including antibiotic activity. In the case of molecular crystalline solids, it is well established that understanding noncovalent interactions remains key to designing or engineering their functional properties. While both aryl boronic acids and phenazine molecules individually represent an important class of compounds, their co-assembly in the crystalline state is of interest within the context of supramolecular chemistry and crystal engineering. Herein, we report the supramolecular features of two newly synthesized cocrystals, which are composed of para-F/CF₃-substituted phenylboronic acids, respectively, and phenazine, as demonstrated by structure analysis by single-crystal X-ray diffraction. Full article

A series of previously poorly studied heterocyclic compounds, 10R-pyrido[4,3-a]phenazines, including the previously unknown parent compound, has been synthesized. The proposed synthetic approach is remarkable for its simplicity, due to the ease of the synthesis of the starting materials from readily available precursors, and is characterized by high yields of the target products, achievable under both acidic and basic catalysis. The paper discusses the synthesis conditions, optimization procedures, and X-ray crystallographic data. Full article

Infections often occur in complex niches consisting of multiple bacteria. Despite the increasing awareness, there is a fundamental gap in understanding which interactions govern microbial community composition. Pseudomonas aeruginosa is frequently isolated from monomicrobial and polymicrobial human infections. This pathogen forms polymicrobial infections with other ESKAPEE pathogens and defies eradication by conventional therapies. By analyzing the competition within co-cultures of P. aeruginosa and representative secondary pathogens that commonly co-infect patients, we demonstrate the antagonism of P. aeruginosa against other ESKAPEE pathogens and the contribution of this pathogen’s multiple quorum-sensing (QS) systems in these interactions. QS is a highly conserved bacterial cell-to-cell communication mechanism that coordinates collective gene expressions at the population level, and it is also involved in P. aeruginosa virulence. Using a collection of P. aeruginosa QS mutants of the three major systems, LasR/LasI, MvfR/PqsABCDE, and RhlR/RhlI, and mutants of several QS-regulated functions, we reveal that MvfR and, to a lesser extent, LasR and RhlR, control competition between P. aeruginosa and other microbes, possibly through their positive impact on pyoverdine, pyochelin, and phenazine genes. We show that MvfR inhibition alters competitive interspecies interactions and preserves the coexistence of P. aeruginosa with the ESKAPEE pathogens tested while disarming the pathogens’ ability to form biofilm and adhere to lung epithelial cells. Our results highlight the role of MvfR inhibition in modulating microbial competitive interactions across multiple species, while simultaneously attenuating virulence traits. These findings reveal the complexity and importance of QS in interspecies interactions and underscore the impact of the anti-virulence approach in microbial ecology and its importance for treating polymicrobial infections. Full article

A biosensor for the determination of glucose, lactate, ethanol and starch in beverages has been developed using enzymes immobilized by a redox-active gel on a screen-printed electrode. A significant improvement proposed for multichannel biosensors, overcoming stability and sensitivity issues by covalently binding phenazine mediators to a biocompatible protein hydrogel, enhancing the packaging of the enzyme. Glucose oxidase (GOx), alcohol oxidase (AOx) and lactate oxidase (LOx) were used as biological materials, as well as a mixture of GOx with γ-amylase (Am). Redox gels were synthesized from bovine serum albumin (BSA) and phenazine derivatives. It was shown that a neutral red-based redox gel combined with single-walled carbon nanotubes is more promising than other substrates for enzyme immobilization. The lower limit of quantification for glucose, ethanol, lactate and starch using these systems is 0.035 mM, 2.3 mM, 15 mM and 2 mg/L, respectively. Biosensors were used to analyze the content of these substances in alcoholic, kvass and fermentation mass. Statistical analysis of the results showed that the values of glucose, ethanol, lactic acid and starch determined using biosensors and obtained by reference methods differ insignificantly. A set of biosensors developed on the basis of specifically selected enzymes is effective for controlling biotechnological processes and can be used as an alternative to classical analytical methods. Full article

With the long-term use of certain types of traditional chemical fungicides, phytopathogen resistance and environmental pollution have made the application of these fungicides face unprecedented challenges. Therefore, using the low toxicity and structural diversity of natural product analogs to develop alternatives has become an important tactic to improve control efficiency and reduce pathogen resistance, as well as environmental risks. In this study, thirty-eight rhein derivatives were synthesized after our continuous efforts aiming to discover new anthraquinone-based antifungal agents. Their structures were characterized by ¹H-NMR, ¹³C-NMR and high-resolution mass spectrometry. The antifungal activities of rhein derivatives were first evaluated against four phytopathogenic fungi. The bioassay results indicated that most derivatives exhibited good antifungal activity against Rhizoctonia solani at 0.5 mM in vitro. Compounds 3e, 3j, 4a, 9d and 10f showed potent activities against R. solani, with inhibition rates over 50% at a low concentration of 0.2 mM in vitro. In particular, compound 10a strongly inhibited the growth of Sclerotinia sclerotiorum, Fusarium graminearum and P. capsica, with EC₅₀ values of 0.079 mM, 0.082 mM and 0.134 mM, respectively, which are comparable to the commercial biofungicide phenazine-1-carboxylic acid (PCA). An in vivo study showed that 10a presented excellent curative and protective activities (92.1% and 91.1%, 0.2 mM) against wheat powdery mildew. The phytotoxicity results indicated that rhein amino acid derivatives could significantly eliminate phytotoxicity to rice and rape and could be safely used in these two crops. The resistance development assay indicated that these rhein derivatives could effectively avoid the risk of resistance development in these two strains of fungi, R. solani and S. sclerotiorum. In conclusion, rhein derivatives can be used for the development of potential agricultural fungicides. Full article

Ralstonia solanacearum is an important pathogen causing bacterial wilt in pepper (Capsicum annuum L.). The concurrent infection of R. solanacearum and root-knot nematodes (Meloidogyne spp.) exacerbates the severity of bacterial wilt in pepper. Utilizing plant endophytic bacteria to control these mixed diseases is a viable strategy. Waltheria indica L. (Sterculiaceae) is a traditional medicine plant. A total of 209 endophytic bacteria were isolated from W. indica, and Pseudomonas aeruginosa W-126 showed an efficient antagonistic effect against R. solanacearum. Based on active compound tracking principles, a compound was isolated through silica gel column chromatography and preparative HPLC combined with TLC analysis. It was identified as phenazine-1-carboxamide (PCN) by spectral techniques (ESI-MS, ¹H-NMR, ¹³C-NMR). PCN displayed excellent inhibitory activity against R. solanacearum, with an EC₅₀ of 64.16 μg/mL in vitro. In addition, it showed certain nematocide activity, with an LC₅₀ value of 118.63 μg/mL at 72 h. PCN also showed certain inhibitory activity against five other phytopathogenic bacteria. The structure−activity relationship indicated that the phenazine skeleton and acylamide groups were the key pharmacophores for the activity of phenazine-related compounds against R. solanacearum. PCN controlled the complex diseases of R. solanacearum and M. incognita in a pot experiment, with respective 51.41 and 39.80% inhibitory rates. The exploration of secondary metabolites of biocontrol bacteria can provide reference for the development of novel and efficient pesticides. Full article

To discover novel fungicides with good inhibitory effects on plant fungal diseases, twenty-five 3-indolyl-3-hydroxy oxindole derivatives (3a–3y) were synthesized. These newly derivatives were characterized by NMR and HRMS. Their antifungal activities against five plant pathogenic fungi were assessed in vitro. Most of the compounds exhibited moderate to excellent antifungal activities against the five pathogenic fungi. Notably, compounds 3t, 3u, 3v, and 3w displayed remarkable and broad-spectrum antifungal activities comparable to or superior to those of the fungicides carvacrol (CA) and phenazine-1-carboxylic acid (PCA). Among them, compound 3u displayed the most excellent antifungal activity against Rhizoctonia solani Kühn (R. solani), with an EC₅₀ of 3.44 mg/L, which was superior to CA (7.38 mg/L) and PCA (11.62 mg/L). Preliminary structure–activity relationship (SAR) results indicated that the introduction of I, Cl, or Br substituents at position 5 of the 3-hydroxy-2-oxindole and indole rings is crucial for compounds to exhibit good antifungal activity. The in vivo antifungal activity assay showed that compound 3u has good curative effects against R. solani. The current results suggest that these compounds are capable of serving as promising lead compounds. Full article

Photo-thermo-electric conversion devices represent a promising technology for converting solar energy into electrical energy. Photothermal materials, as a critical component, play a significant role in efficient conversion from solar energy into thermal energy and subsequently electrical energy, thereby directly influencing the overall system’s efficiency in solar energy utilization. However, the application of single-component photothermal materials in photo-thermo-electric conversion systems remains limited. The exploration of novel photothermal materials with broad-spectrum absorption, a high photothermal conversion efficiency (PCE), and a robust output power density is highly desired. In this study, we investigated a black cuprous halide compound, [Cu₂Cl₂PA]_n (1, PA = phenazine), which exhibits broad-spectrum absorption extending into the near-infrared (NIR) region. Compound 1 demonstrated a high NIR-I PCE of 50% under irradiation with an 808 nm laser, attributed to the metal-to-ligand charge transfer (MLCT) from the Cu(I) to the PA ligands and the strong intermolecular π–π interactions among the PA ligands. Furthermore, the photo-thermo-electric conversion device constructed using compound 1 achieved a notable output voltage of 261 mV and an output power density of 0.92 W/m² under the 1 Sun (1000 W/m²) xenon lamp. Full article

Pseudomonas aeruginosa is a metabolically versatile opportunistic pathogen capable of surviving in a range of environments. The major contribution to these abilities relies on virulence factor production, e.g., exotoxins, phenazines, and rhamnolipids, regulated through a hierarchical system of communication, named quorum sensing (QS). QS involves the production, release, and recognition of two classes of diffusible signal molecules: N-acyl-homoserine lactones and alkyl-quinolones. These present a central role during P. aeruginosa infection, regulating bacterial virulence and the modulation of the host immune system. The influence of this arsenal of virulence factors on bacterial–host interaction makes P. aeruginosa a highly potential platform for the development of biopharmaceuticals. Here, we comprehensively reviewed the therapeutical applications of P. aeruginosa virulence factors and quorum sensing signaling molecules on pathological conditions, ranging from infections and inflammation to cancer disease. Full article

Background. Acetyl phosphate (AcP) is a microbial intermediate involved in the central bacterial metabolism. In bacteria, it also functions as a donor of acetyl and phosphoryl groups in the nonenzymatic protein acetylation and signal transduction. In host, AcP was detected as an intermediate of the pyruvate dehydrogenase complex, and its appearance in the blood was considered as an indication of mitochondrial breakdown. In vitro experiments showed that AcP is a powerful agent of nonenzymatic acetylation of proteins. The influence of AcP on isolated mitochondria has not been previously studied. Methods. In this work, we tested the influence of AcP on the opening of the mitochondrial permeability transition pore (mPTP), respiration, and succinate dehydrogenase (SDH) activity under neutral and alkaline conditions stimulating the nonenzymatic acetylation using polarographic, cation-selective, and spectrophotometric methods. Results. It was found that AcP slowed down the opening of the mPTP by calcium ions and decreased the efficiency of oxidative phosphorylation and the activity of SDH. These effects were observed only at neutral pH, whereas alkaline pH by itself caused a decrease in these functions to a much greater extent than AcP. AcP at a concentration of 0.5–1 mM decreased the respiratory control and the swelling rate by 20–30%, while alkalization decreased them twofold, thereby masking the effect of AcP. Presumably, the acetylation of adenine nucleotide translocase involved in both the opening of mPTP and oxidative phosphorylation underlies these changes. The intermediate electron carrier phenazine methosulfate (PMS), removing SDH inhibition at the ubiquinone-binding site, strongly activated SDH under alkaline conditions and, partially, in the presence of AcP. It can be assumed that AcP weakly inhibits the oxidation of succinate, while alkalization slows down the electron transfer from the substrate to the acceptor. Conclusions. The results show that both AcP and alkalization, by promoting nonmetabolic and nonenzymatic acetylation from the outside, retard mitochondrial functions. Full article