Synthesis, characterization, in silico molecular docking, and antibacterial activities of some new nitrogen-heterocyclic analogues based on a p-phenolic unit

Giardia duodenalis flavohemoglobin is a target of 5-nitroheterocycle and benzimidazole compounds acting as enzymatic inhibitors or subversive substrates

Giardia duodenalis causes giardiasis in humans, companion, livestock and wild animals. Control of infection involves drugs as benzimidazoles (e.g., albendazole, ABZ) and 5-nitroheterocyclics [5-NHs: metronidazole (MTZ), furazolidone (FZD), nitazoxanide (NTZ)] as first-line agents. During infection, Giardia is exposed to immune and pro-oxidant host responses involving nitric oxide (NO). In Giardia, NO is detoxified by a flavohemoglobin (gFlHb), a heme-containing enzyme which is absent in mammals. gFlHb has NO dioxygenase and NADH oxidase activities converting NO into nitrate and producing a superoxide anion (O2•-) that causes oxidative stress and parasite death. The modulation of gFlHb activities may provide novel approaches for treatment of giardiasis. We investigated the capacity of selected benzimidazole-2-carbamates (BZCs: ABZ, oxibendazole, nocodazole), non-BZCs (thiabendazole), an ehtylphenylcarbamate (LQM-996) and 5-NHs (MTZ, NTZ, FZD and some derivatives) to bind to recombinant gFlHb at the heme group, modifying NADH consumption activity and/or inducing ROS production. Of these, BZCs and NTZ bind to heme and increased O2•- production (i.e. caused enzyme subversion), whereas MTZ binds to heme but inhibited NADH consumption. LQM-996 decreased NADH consumption and two out of four NTZ derivatives altered NADH oxidase activity. In silico docking and molecular dynamics studies suggested the interaction of distinct drug moieties in ABZ and NTZ with gFlHb sites involved in NADH and NO catalysis. These findings provide new insights on gFlHb as a novel target of BZCs, MTZ and NTZ, and provides a useful platform to assess the compounds binding capacity to gFlHb prior to experimental and clinical trials in giardiasis.

New 1,3-diphenyl-1H-pyrazol-5-ols as anti-methicillin resistant Staphylococcus aureus agents: Synthesis, antimicrobial evaluation and in silico studies

In the present work, two hybrid series of pyrazole-clubbed pyrimidine and pyrazole-clubbed thiazole compounds 3-21 from 4-acetyl-1,3-diphenyl-1H-pyrazole-5(4H)-ole 1 were synthesized as novel antimicrobial agents. Their chemical structures were thoroughly elucidated in terms of spectral analyses such as IR, 1H NMR, 13C NMR and mass spectra. The compounds were in vitro evaluated for their antimicrobial efficiency against various standard pathogen strains, gram -ive bacteria (Pseudomonas aeruginosa, Klebsiella pneumonia), gram + ive bacteria (MRSA, Bacillus subtilis), and Unicellular fungi (Candida albicans) microorganisms. The ZOI results exhibited that most of the tested molecules exhibited inhibition potency from moderate to high. Where compounds 7, 8, 12, 13 and 19 represented the highest inhibition potency against most of the tested pathogenic microbes comparing with the standard drugs. In addition, the MIC results showed that the most potent molecules 7, 8, 12, 13 and 19 showed inhibition effect against most of the tested microbes at low concentration. Moreover, the docking approach of the newly synthesized compounds against DNA gyrase enzyme was performed to go deeper into their molecular mechanism of antimicrobial efficacy. Further, computational investigations to calculate the pharmacokinetics parameters of the compounds were performed. Among them 7, 8, 12, 13 and 19 are the most potent compounds revealed the highest inhibition efficacy against most of the tested pathogenic microbes comparing with the standard drugs.

Deciphering the Mechanism of MRSA Targeting Copper(II) Complexes of NN2 Pincer-Type Ligands

WHO lists AMR as one of the top ten global public health issues. Therefore, constant effort is needed to develop more efficient antimicrobial drugs. As a result, earth-abundant transition-metal complexes have emerged as an excellent solution. In this regard, new aminoquinoline-based copper(II) pincer complexes 1-3 were designed, synthesized, and characterized by modern spectroscopic techniques. It is worth mentioning that, at the highest concentration (1024 μg/mL) of complexes (1-3), the hemolysis was found to be <15%, implying their less toxicity. Further, the complexes effectively interfered with the growth of Gram positive MRSA and the fungus Candida albicans. Among them, complex 2 was promising (MIC = 16 μg/mL) against MRSA, which was better than the known antibacterial drug kanamycin (64 μg/mL) under identical conditions. The Alamar blue cell viability test and the MBC/MFC identified by spot assay were in accordance with MIC values. Moreover, the insilico studies explained the most probable mechanism of action as inhibition of cell wall biosynthesis and dysfunction of antibiotic sensing proteins. Similarly, the antifungal action might be due to the cell surface adhesion protein dysfunction by the complexes. Furthermore, we are expecting to draw these compounds for clinical applications.

Green synthesis, biological and molecular docking of some novel sulfonamide thiadiazole derivatives as potential insecticidal against Spodoptera littoralis

Although crop plants provide the majority of human food, pests and insects frequently cause huge economic losses. In order to develop innovative insecticidal compounds with low toxicity and a positive environmental impact, we developed new N-(4-sulfamoylphenyl)-1,3,4-thiadiazole-2-carboxamide derivatives (2-12). With the use of spectroscopic techniques and elemental data, the chemical structure of these new compounds was meticulously clarified. The toxicological and biological effects of the synthesized compound of the cotton leafworm Spodoptera littoralis (Boisduval, 1833) under laboratory conditions were also investigated. Regarding the determined LC50 values, compounds 3, 7, 8, and 10 showed the most potent toxic effect with LC50 values of 29.60, 30.06, 27.65 and 29.01 ppm, respectively. A molecular docking investigation of twelve synthetic compounds (from compound 2 to compound 12) was performed against AChE (Acetylcholinesterase). There was a wide range of binding affinities shown by these compounds. This work suggests that these substances may have insecticidal and AChE inhibitory properties, and it may be possible to further explore them in the process of creating pesticides that target AChE.

Design, synthetic approach, in silico molecular docking and antibacterial activity of quinazolin-2,4-dione hybrids bearing bioactive scaffolds

Antimicrobial resistance (AMR) is one of ten global public health threats facing humanity. This created the need to identify and develop effective inhibitors as antimicrobial agents. In this respect, quinazolin-2,4-dione hybrids bearing N-heterocyclic cores such as pyrrolidine-2,5-dione, pyrazole and oxadiazole and/or bioactive scaffolds such as hydrazone, amide, sulfonamide, azomethine, and thiourea linkage are described for design, synthesis, antibacterial investigation, and in silico studies. The characterization of the target compounds was accomplished by elemental analysis and various spectroscopic data like FT-IR, 1H-NMR, 13C-NMR and MS. The antibacterial evaluation was achieved for the newly synthesized compounds using two G -ve bacteria (Escherichia coli ATCC 25955 and Pseudomonas aeruginosa ATCC 10145), and two G +ve bacteria (Bacillus subtilis ATCC 6633 and Staphylococcus aureus NRRL B-767). Synthesized compounds exhibited various activities against the tested pathogens, the results revealed that compound 3c exhibited a characteristic antimicrobial efficacy against all the tested pathogenic strains at a concentration lower than the tested standard drug ranging from 2.5 to 10 μg ml-1. Moreover, the molecular docking study against the target S. aureus tyrosyl-tRNA synthetase (PDB ID: 1JIJ) was carried out to investigate the mechanism of action of the prepared compounds, which is in line with an in vitro study. Most new compounds exhibited zero violation of Lipinski's rule (Ro5). These candidate molecules have shown promising antibacterial activity. Among these molecules, compound 3c with di-hydroxyl groups on two phenyl rings at position-4 exhibited a promising potent antibacterial inhibitory effect. Further SAR analysis reveals that a greater number of hydroxyl groups in an organic compound might be crucial for antibacterial efficacy. These findings demonstrate the potential activity of compound 3c as an antibacterial agent.

In silico study to identify novel potential thiadiazole-based molecules as anti-Covid-19 candidates by hierarchical virtual screening and molecular dynamics simulations

In the present study, a new category of 1,3,4-thiadiazoles was developed by submitting methyl 2-(4-hydroxy-3-methoxybenzylidene) hydrazine-1-carbodithioate to react with the appropriate hydrazonoyl halides in presence of few drops of diisopropyl ethyl amine. The chemical structures of the newly synthesized derivatives were inferred by means of their micro-analytical and spectral data. Utilizing combined molecular docking and molecular dynamics techniques, the binding affinities and features of the synthesized compounds were evaluated against four SARS-CoV-2 target enzymes, namely, main protease (M^pro), papain-like protease (PL^pro), RNA-dependent RNA polymerase (RdRp), and receptor-binding domain (RBD) of the spike protein. Compound 7 demonstrated promising binding affinities with the target enzymes M^pro, PL^pro, RdRp, and RBD with docking scores of −11.4, −9.4, −8.2, and −6.8 kcal/mol, respectively. In addition, compound 7 exhibited MM-GBSA//100 ns MD docking score of −35.9 kcal/mol against M^pro. Structural and energetic analyses revealed the stability of the 7-M^pro complex over 100 ns MD simulations. In addition, compound 7 obeyed Lipinski’s rule of five, as it has acceptable absorption, distribution, and oral bioavailability inside the body. Therefore, compound 7 is considered as a promising starting point for designing potential therapeutic agents against Covid-19.