Synthesis and bioactivities of Phenazine-1-carboxylic acid derivatives based on the modification of PCA carboxyl group

Evaluation of Phenazine Derivatives from the Lichen-Associated Streptomyces flavidovirens as Potent Antineuroinflammatory Agents In Vitro and In Vivo

Eighteen nitrogen-containing compounds (1-18) were isolated from cultures of the lichen-associated Streptomyces flavidovirens collected from the Qinghai-Tibet Plateau, including seven phenazine derivatives with three new ones, named subphenazines A-C (2-4), two new furan pyrrolidones (8-9), and nine known alkaloids. The structures were elucidated by spectroscopic data analysis, and absolute configurations were determined by single-crystal X-ray diffraction and ECD calculations. The phenazine-type derivatives, in particular compound 3, exhibited significantly better antineuroinflammatory activity than other isolated compounds (8-18). Compound 3 inhibited the release of proinflammatory cytokines including IL-6, TNF-α, and PGE2, and the nuclear translocation of NF-κB; it also reduced the oxidative stress and activated the Nrf2 signaling pathway in LPS-induced BV2 microglia cells. In vivo anti-inflammatory activity in zebrafish indicated that 3 inhibited LPS-stimulated ROS generation. These findings suggested that compound 3 might be a potent antineuroinflammatory agent through the regulation of the NF-κB/Nrf2 signaling pathways.

Recent Advances in Design and Development of Diazole and Diazine Based Fungicides (2014-2023)

With fungal diseases posing a major threat to agricultural production, the application of fungicides to control related diseases is often considered necessary to ensure the world's food supply. The search for new bioactive agents has long been a priority in crop protection due to the continuous development of resistance against currently used types of active compounds. Heterocyclic compounds are an inseparable part of the core structures of numerous lead compounds, these rings constitute pharmacophores of a significant number of fungicides developed over the past decade by agrochemists. Among heterocycles, nitrogen-based compounds play an essential role. To date, diazole (imidazole and pyrazole) and diazine (pyrimidine, pyridazine, and pyrazine) derivatives make up an important series of synthetic fungicides. In recent years, many reports have been published on the design, synthesis, and study of the fungicidal activity of these scaffolds, but there was a lack of a comprehensive classified review on nitrogen-containing scaffolds. Regarding this issue, here we have reviewed the published articles on the fungicidal activity of the diazole and diazine families. In current review, we have classified the molecules synthesized so far based on the size of the ring.

Design, synthesis, structure elucidation, antimicrobial, molecular docking, and SAR studies of novel urea derivatives bearing tricyclic aromatic hydrocarbon rings

The targeted compounds were prepared using both (9H-fluoren-9-ylidene)hydrazine (1) and 10H-phenothiazine (2) as starting materials. The treatment of 1 or 2 with different isocyanates afforded the title compounds 7a-d, 8a, and 8b in excellent yield. All compounds were characterized and ascertained by infrared, nuclear magnetic resonance, and elemental analyses as well as single-crystal X-ray diffraction. The antimicrobial efficiency of all was tested in vitro, and a noticeable inhibition activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans was obtained by compounds 7a, 7b, 8a, and 8b. Moreover, the biofilm mechanism activity was strongly inhibited by compounds 7b and 8b for all bacterial pathogens, with a percentage ratio of more than 55%. The findings from the molecular docking simulation revealed that compounds 7a, 7b, 8a, and 8b exhibited favorable binding energies and interacted effectively with the active sites of sterol 14-demethylase, dihydropteroate synthase, gyrase B, LasR (major transcriptional activator of P. aeruginosa), and carbapenemase for C. albicans, S. aureus, B. subtills, K. pneumoniae, and P. aeruginosa, respectively. These results suggest that the compounds have the potential to inhibit the activity of these enzymes and demonstrate promising antimicrobial properties. Moreover, the in silico evaluation of drug likeness and absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles for compounds 7a, 7b, 8a, and 8b demonstrated their compatibility with Lipinski's, Ghose's, Veber's, Muegge's, and Egan's rules. These findings suggest that these compounds possess favorable physicochemical properties, making them promising candidates for continued drug development efforts.

Discovery of a Highly Potent Oxysterol Receptor GPR183 Antagonist Bearing the Benzo[d]thiazole Structural Motif for the Treatment of Inflammatory Bowel Disease (IBD)

Accumulating evidence has demonstrated a critical pathological role of oxysterol receptor GPR183 in various inflammatory and autoimmune diseases, including inflammatory bowel disease (IBD). However, the currently reported GPR183 antagonists are very limited and not qualified for in vivo studies due to their inferior druglike properties. Herein, we conducted a structural elaboration focusing on improving its PK and safety profile based on a reference antagonist NIBR189. Of note, compound 33, bearing an aminobenzothiazole motif, exhibited reduced hERG inhibition, improved PK properties, and robust antagonistic activity (IC50 = 0.82 nM) with high selectivity against GPR183. Moreover, compound 33 displayed strong in vitro antimigration and anti-inflammatory activity in monocytes. Oral administration of compound 33 effectively improved the pathological symptoms of DSS-induced experimental colitis. All of these findings demonstrate that compound 33 is a novel and promising GPR183 antagonist suitable for further investigation to treat IBD.

Recent Developments in the Biological Activities, Bioproduction, and Applications of Pseudomonas spp. Phenazines

Phenazines are a large group of heterocyclic nitrogen-containing compounds with demonstrated insecticidal, antimicrobial, antiparasitic, and anticancer activities. These natural compounds are synthesized by several microorganisms originating from diverse habitats, including marine and terrestrial sources. The most well-studied producers belong to the Pseudomonas genus, which has been extensively investigated over the years for its ability to synthesize phenazines. This review is focused on the research performed on pseudomonads' phenazines in recent years. Their biosynthetic pathways, mechanism of regulation, production processes, bioactivities, and applications are revised in this manuscript.

Activity of bacteria isolated from bats against Pseudogymnoascus destructans in China

White-nose syndrome, a disease that is caused by the psychrophilic fungus Pseudogymnoascus destructans, has threatened several North America bat species with extinction. Recent studies have shown that East Asian bats are infected with P. destructans but show greatly reduced infections. While several factors have been found to contribute to these reduced infections, the role of specific microbes in limiting P. destructans growth remains unexplored. We isolated three bacterial strains with the ability to inhibit P. destructans, namely, Pseudomonas yamanorum GZD14026, Pseudomonas brenneri XRD11711 and Pseudomonas fragi GZD14479, from bats in China. Pseudomonas yamanorum, with the highest inhibition score, was selected to extract antifungal active substance. Combining mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy analyses, we identified the active compound inhibiting P. destructans as phenazine-1-carboxylic acid (PCA), and the minimal inhibitory concentration (MIC) was 50.12 μg ml-1 . Whole genome sequencing also revealed the existence of PCA biosynthesis gene clusters. Gas chromatography-mass spectrometry (GC-MS) analysis identified volatile organic compounds. The results indicated that 10 ppm octanoic acid, 100 ppm 3-tert-butyl-4-hydroxyanisole (isoprenol) and 100 ppm 3-methyl-3-buten-1-ol (BHA) inhibited the growth of P. destructans. These results support that bacteria may play a role in limiting the growth of P. destructans on bats.

Phenazine 1-carboxylic acid Producing Seed Harbored Endophytic Bacteria from Cultivated Rice Variety of Kerala and Its Broad Range Antagonism to Diverse Plant Pathogens

Endophytic microorganisms residing within the diverse parts of plants play a significant role in the plant growth and defense response. In the case of the vertically transmitted seed-borne endophytes, they form the promising initiator of the juvenile plant microbiome by supporting the growth and establishment of the seedlings. Hence, the current study emphasizes the isolation and screening of plant beneficial traits of seed endophytes from the cultivated rice variety Jyothi of Kerala, India. Among the 14 bacterial endophytes obtained in the study, the isolate S3 was found to have promising activity against the phytopathogens such as Fusarium oxysporum, Pythium aphanidermatum, Pythium myriotylum, Phytophthora infestans, Rhizoctonia solani, Colletotrichum acutatum, and Sclerotium rolfsii. The isolate S3 was further identified as Paenibacillus polymyxa by the 16S rRNA-based sequence analysis. Furthermore, the isolate was confirmed for its capability for hydrogen cyanide (HCN) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, biofilm formation, and nitrogen fixation. The P. polymyxa S3 was also found to have the potential to provide post-harvest protection to the rice kernels from Sclerotium rolfsii. By the LC-MS/MS analysis, the organism was confirmed for the production of phenazine 1-carboxylic acid which could be the prime chemical basis of its antifungal activity. The in vivo plant growth evaluation has also demonstrated the root length enhancement effect of P. polymyxa S3 in Vigna unguiculata. Here, the root length of P. polymyxa S3-treated plant was enhanced to 12.44 ± 0.58223 cm when compared with distilled water control (10.261 ± 0.38151 cm) and the observed change was statistically significant as per the analysis of variance at P value less than 0.05. Based on all these properties, the isolated P. polymyxa S3 could be considered as a promising agent to be used for the development of competent plant probiotic formulations.

Antifungal and insecticidal activities of rhein derivatives: synthesis, characterization and preliminary structure-activity relationship studies

There is an urgent need to replace highly polluting pesticides with environmentally friendly green pesticides of high efficiency and low toxicity, because of the growing concern for quality and safety of agricultural products. To discover new pesticides with diverse chemical structures from natural products, a series of rhein derivatives 3a-9b were designed, synthesized, and evaluated for their antifungal activity and insecticidal activity. The bioassay showed that some compounds exhibited moderate antifungal activity against Rhizoctonia solani, but lower activity against the other five pathogens. Surprisingly, most compounds displayed potent insecticidal activity against Spodoptera litura and Tetranychus cinnabarinus at a concentration of 2 μmol/mL. In particular, compounds 3a, 5a and 3 b exhibited potent insecticidal activities against S. litura at 72 h, with mortality rates of 100%, 100% and 92.1%, respectively, which were equivalent to that of the insecticide fipronil (100%). Their structure-activity relationships were also discussed. The findings of this experiment provide helpful research ideas for the development of these rhein derivatives as novel natural product-based pesticides in crop protection.

Synthesis and fungicidal activity of phenazine-1-carboxylic triazole derivatives

A total of 15 novel-substituted 3-(benzylsulfanyl)-1H-1,2,4-triazol-5-ylamine and 10 novel-substituted 3-benzylmercapto-1,2,4-triazol derivatives were synthesized based on the natural product phenazine-1-carboxylic acid (PCA). Their structures were confirmed by ¹H-NMR, ¹³C-NMR, HRMS, and X-ray. Most substituted 3-benzylmercapto-1,2,4-triazol derivatives displayed very strong fungicidal activity against one or multiple plant pathogens in vitro and in vivo. Compounds 8b, 8h, and 8i showed a broad spectrum of fungicidal activity. Further field experiments indicated that compounds 8b, 8c, and 8h displayed better efficacy against rice blast (Pyricularia oryzae) than PCA. These data demonstrate that compounds 8b, 8c, and 8h are promising fungicidal candidates, deserving further studies.[Formula: see text].

Effect of introducing amino acids into phenazine-1-carboxylic acid on phloem mobility

To develop new phenazine carboxylic acid derivatives with better phloem mobility, five novel 7-amino acid substituted phenazine-1-carboxylic acids were synthesised by introducing amino acids into PCA at the 7-position. The phloem mobility experiments in Ricinus communis seedlings showed that retaining the carboxyl group of PCA and conjugating amino acids to its phenazine ring can also endow PCA with phloem mobility. Comparing our previous research, we found the amino acids substituted at 7-position on phenazine ring of PCA could clearly enhance the phloem mobility of PCA than that of amino acids conjugated with carboxyl group. Especially, the phloem transport concentration of the compound 7-L-isoleucine substituted PCA (7d) was 21 times higher than PCA-L-isoleucine conjugate (8d). These data suggest that the introduction of amino acids at different structural sites on the phenazine ring could effectively enhance the phloem mobility of PCA and it is worth a further study.

The influence of steric configuration of phenazine-1-carboxylic acid-amino acid conjugates on fungicidal activity and systemicity

BACKGROUND

Conjugating an amino acid onto existing fungicidal parent structures has been demonstrated to be an effective way to endow non-phloem mobile fungicides with phloem mobility. To alter the systemicity of the fungicide PCA (phenazine-1-carboxylic acid), 10 amino acids derivatives of this fungicide were designed and synthesized, and their synthesis, characterization, phloem and xylem mobility in Ricinus communis L, and their fungicidal activity in vitro are described.

RESULTS

The systemicity experiments in Ricinus communis system demonstrated that all conjugates exhibited obvious phloem mobility compared with non-phloem-mobile PCA, and the introduction of an L-amino acid to PCA more greatly enhanced the phloem mobility. The five D-amino acid conjugates exhibited higher xylem mobility than that of PCA and of each corresponding L-amino acid conjugate. Most conjugates were found to exhibit moderate in vitro fungicidal activities against six pathogenic fungi, which were lower than that of PCA. The results of the bioassay showed fungicidal activities of PCA-amino acid conjugates associated not only with different amino acids, but also with their conformation. Conjugation with D-amino acid contributed to the in vitro fungicidal activities of PCA-amino acid conjugates.

CONCLUSIONS

The current research offers a new strategy for enhancing the systemicity of non-phloem-mobile fungicides and presents some useful information on the effects of introducing amino acids of different steric configurations on the fungicidal activity, phloem and xylem mobility of the parent fungicide. © 2019 Society of Chemical Industry.

Synthesis and antifungal evaluation of PCA amide analogues

To improve the physical and chemical properties of phenazine-1-carboxylic acid (PCA) and find higher antifungal compounds, a series of PCA amide analogues were designed and synthesized and their structures were confirmed by ¹H NMR, HRMS, and X-ray. Most compounds showed some antifungal activities in vitro. Particularly, compound 3d exhibited inhibition effect against Pyriculariaoryzac Cavgra with EC₅₀ value of 28.7 μM and compound 3q exhibited effect against Rhizoctonia solani with EC₅₀ value of 24.5 μM, more potently active than that of the positive control PCA with its EC₅₀ values of 37.3 μM (Pyriculariaoryzac Cavgra) and 33.2 μM (Rhizoctonia solani), respectively.

Synthesis and fungicidal activity of 1,3,4-oxadiazol-2-yl thioether derivatives containing a phenazine-1-carboxylic acid scaffold

To find new higher fungicidal activities lead compounds and develop new eco-friendly agrochemicals, natural product phenazine-1-carboxylic acid (PCA) as scaffold, a series of 1,3,4-oxadiazol-2-yl thioether derivatives was synthesized and bio-assayed. The results reveal that most target compounds possessed moderate to good fungicidal activities against R. solani, S. sclerotioru and P. oryzac Cavgra. Compounds 6n and 6o exhibit more than 90% bioactivity against S. sclerotioru. The EC₅₀ value of compounds 6n and 6o are 11.16 and 30.47 μM respectively, in particular, compound 6n show equal activity against S. sclerotioru to PCA (10.49 μM). This result provides a valuable lead compound for further studies.

Design, Synthesis, Phloem Mobility, and Bioactivities of a Series of Phenazine-1-Carboxylic Acid-Amino Acid Conjugates

Developing fungicides with phloem mobility that can be applied to leaves to control root or vascular pathogens has long been desirable. To achieve this goal, an efficient and economical strategy involves introducing an amino acid into the existing highly active parent pesticide molecule. Hence, 12 L-phenazine-1-carboxylic acid (PCA)-amino acid conjugates 4a⁻l were designed and synthesized via a simple synthetic route. In vitro bioassays results showed that all synthesized compounds 4a⁻l exhibited certain fungicidal activities against six tested fungi. Compound 4c exhibited relatively good fungicidal activity against Rhizoctonia solani, and the EC₅₀ value was 0.084 ± 0.006 mmol/L. The phloem mobility experiments revealed that introducing an amino acid to PCA could effectively endow PCA with phloem mobility in R. communis L. Among them, nine conjugates were found in phloem sap, and L-PCA-Valine 4d exhibited the highest phloem mobility. Analysis results from the prediction of the Kleier model indicated that an active carrier-mediated mechanism may be involved in L-PCA-amino acid conjugates-a result that needs to be confirmed and complemented with further tests. The current research provides useful data for modifying non-phloem-mobile fungicidal molecules to phloem-mobile types.

Enhancement of iodinin solubility by encapsulation into cyclodextrin nanoparticles

Phenazine is known to regroup planar nitrogen-containing heterocyclic compounds. It was used here to enhance the bioavailability of the biologically important compound iodinin, which is near insoluble in aqueous solutions. Its water solubility has led to the development of new formulations using diverse amphiphilic α-cyclodextrins (CDs). With the per-[6-desoxy-6-(3-perfluorohexylpropanethio)-2,3-di-O-methyl]-α-CD, we succeeded to get iodinin-loaded nanoformulations with good parameters such as a size of 97.9 nm, 62% encapsulation efficiency and efficient control release. The study presents an interesting alternative to optimizing the water solubility of iodinin by chemical modifications of iodinin.

Drug design based on pentaerythritol tetranitrate reductase: synthesis and antibacterial activity of Pogostone derivatives

We performed molecular docking studies of Pogostone with PETNR and analyzed structure–activity relationships, which guided the structure design and the subsequent facile organocatalytic synthesis of Pogostone derivatives.