Development of novel indolin-2-one derivative incorporating thiazole moiety as DHFR and quorum sensing inhibitors: Synthesis, antimicrobial, and antibiofilm activities with molecular modelling study

Thiourea compounds as multifaceted bioactive agents in medicinal chemistry

Microbial resistance (MR) and cancer are global healthcare pitfalls that have caused millions of deaths and pose a significant pharmaceutical challenge, with clinical cases increasing. Thioureas are preferred structures in medicinal chemistry, chemosensors, and organic synthesis platforms. In fact, thiourea (TU) moieties serve as a common framework for several medications and bioactive substances, demonstrating a wide range of therapeutic and pharmacological accomplishments. The integration of the thiourea moiety into a diverse range of organic molecules has resulted in very flexible compounds with widespread uses in medicinal chemistry. Moreover, for over a century, TU and its metal complexes have been characterized for their biological activity. Finally, we provide an assessment and future outlook of different organo-thiourea derivatives, from the very beginning to the most recent discoveries in medicinal activity.

Spectroscopic, Structural Analysis, Molecular Orbital, Molecular Docking, and Antibacterial Activity of the Thiocarbohydrazone Ligand and Its Complexes

New thiocarbohydrazone ligand (N′‐((E)‐3,3‐diphenyl‐2,3‐dihydro‐1H‐inden‐1‐ylidene)‐2‐((Z)‐2‐oxoindolin‐3‐ylidene)hydrazine‐1‐carbothiohydrazide; H2L) and its Co (II), Ni (II), Fe (III), Cu (II), Cd (II), Zn (II), and Mn (II) complexes were prepared in good yields ranging from 60% to 90% and characterized by spectroscopic and analytical tools. Uv–vis, magnetic measurements, molar conductivity, 1H‐NMR spectra, elemental analyses, and FT‐IR were performed. The structural formula for the examined ligand was improved using the Gaussian09 tool. The morphology of the thiocarbohydrazone ligand and metal complexes was demonstrated using a scanning electron microscope. The prepared thiocarbohydrazone ligand and its complexes were evaluated for their antimicrobial properties against Streptococcus mutans and Staphylococcus aureus as G‐positive bacteria; Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa as G‐negative bacteria; and some species of fungi as Aspergillus niger and Candida albicans. It was found that thiocarbohydrazone ligand was less biologically active than the targeted complexes as indicated from the obtained inhibition zone diameters. The interaction between the ligand and the amino acids of the proteins of G‐positive bacteria (Staphylococcus typhus‐3ty7), G‐negative bacteria (E. coli‐3t88), and fungi (C. albicans‐5k04) as receptors was investigated using molecular docking study to correlate the experimental and theoretical observations.

Antibacterial and antifungal pyrazoles based on different construction strategies

The growing prevalence of microbial infections, and antimicrobial resistance (AMR) stemming from the overuse and misuse of antibiotics, call for novel therapeutic agents, particularly ones targeting resistant microbial strains. Scientists are striving to develop innovative agents to tackle the rising microbial infections and abate the risk of AMR. Pyrazole, a five-membered heterocyclic compound belonging to the azole family, is a versatile scaffold and serves as a core structure in many drugs with antimicrobial and other therapeutic effects. In this review, we have updated pyrazole-based antibacterial and antifungal agents mainly developed between 2016 and 2024, by combining with diverse pharmacophores such as coumarin, thiazole, oxadiazole, isoxazole, indole, etc. Meanwhile, the various strategies (molecular hybridization, bioisosterism, scaffold hopping, multicomponent reactions, and catalyst-free synthesis) for integrating different functional groups with the pyrazole ring are discussed. Additionally, structure-activity relationships of these pyrazole derivatives, i.e., how structural modifications impact their selectivity and therapeutic potential against bacterial and fungal strains, are highlighted. This review provides insights into designing next-generation antimicrobials to combat AMR, and offers valuable perspectives to the scientists working on heterocyclic compounds with diverse bioactivities.

Synthesis and Antimicrobial Activity of 3-Alkylidene-2-Indolone Derivatives

The escalating threat of antibiotic-resistant bacteria and fungi underscores an urgent need for new antimicrobial agents. This study aimed to synthesize and evaluate the antimicrobial activities of two series of 3-alkylidene-2-indolone derivatives. We synthesized 32 target compounds, among which 25 exhibited moderate to high antibacterial or antifungal activities. Notably, compounds 10f, 10g, and 10h demonstrated the highest antibacterial activity with a minimum inhibitory concentration (MIC) of 0.5 μg/mL, matching the activity of the positive control gatifloxacin against three Gram-positive bacterial strains: Staphylococcus aureus ATCC 6538, 4220, and Methicillin-resistant Staphylococcus aureus ATCC 43300. Moreover, the three most active compounds 10f, 10g, and 10h were evaluated for their in vitro cytotoxicity in the HepG2 cancer cell line and L-02; only compound 10h was found to exert some level of cytotoxicity. These findings suggest that the synthesized 3-alkylidene-2-indolone derivatives hold potential for further development as antibacterial agents.

Current development and structure-activity relationship study of berberine derivatives

Berberine is a quaternary ammonium isoquinoline alkaloid derived from traditional Chinese medicines Coptis chinensis and Phellodendron chinense. It has many pharmacological activities such as hypoglycemic, hypolipidemic, anti-tumor, antimicrobial and anti-inflammatory. Through structural modifications at various sites of berberine, the introduction of different groups can change berberine's physical and chemical properties, thereby improving the biological activity and clinical efficacy, and expanding the scope of application. This paper reviews the research progress and structure-activity relationships of berberine in recent years, aiming to provide valuable insights for the exploration of novel berberine derivatives.

Thiazolation of phenylthiosemicarbazone to access new thiazoles: anticancer activity and molecular docking

Aim: Novel thiazole hybrids were synthesized via thiazolation of 4-phenylthiosemicarbazone (4). Materials & methods: The anticancer activity against the NCI 60 cancer cell line panel. Results: Methyl 2-(2-((1-(naphthalen-2-yl)ethylidene)hydrazineylidene)-4-oxo-3-phenylthiazolidin-5-ylidene)acetate (6a) showed significant anticancer activity at 10 μM with a mean growth inhibition (GI) of 51.18%. It showed the highest cytotoxic activity against the ovarian cancer OVCAR-4 with an IC50 of 1.569 ± 0.06 μM. Compound 6a inhibited PI3Kα with IC50 = 0.225 ± 0.01 μM. Moreover, compound 6a revealed a decrease of Akt and mTOR phosphorylation in OVCAR-4 cells. In addition, antibacterial activity showed that compounds 11 and 12 were the most active against Staphylococcus aureus. Conclusion: Compound 6a is a promising molecule that could be a lead candidate for further studies.

Small Schiff Base Molecules-A Possible Strategy to Combat Biofilm-Related Infections

Microorganisms participating in the development of biofilms exhibit heightened resistance to antibiotic treatment, therefore infections involving biofilms have become a problem in recent years as they are more difficult to treat. Consequently, research efforts are directed towards identifying novel molecules that not only possess antimicrobial properties but also demonstrate efficacy against biofilms. While numerous investigations have focused on antimicrobial capabilities of Schiff bases, their potential as antibiofilm agents remains largely unexplored. Thus, the objective of this article is to present a comprehensive overview of the existing scientific literature pertaining to small molecules categorized as Schiff bases with antibiofilm properties. The survey involved querying four databases (Web of Science, ScienceDirect, Scopus and Reaxys). Relevant articles published in the last 10 years were selected and categorized based on the molecular structure into two groups: classical Schiff bases and oximes and hydrazones. Despite the majority of studies indicating a moderate antibiofilm potential of Schiff bases, certain compounds exhibited a noteworthy effect, underscoring the significance of considering this type of molecular modeling when seeking to develop new molecules with antibiofilm effects.

Design, Synthesis, and Evaluation of New Hybrid Derivatives of 5,6-Dihydro-4H-pyrrolo[3,2,1-ij]quinolin-2(1H)-one as Potential Dual Inhibitors of Blood Coagulation Factors Xa and XIa

Cardiovascular diseases caused by blood coagulation system disorders are one of the leading causes of morbidity and mortality in the world. Research shows that blood clotting factors are involved in these thrombotic processes. Among them, factor Xa occupies a key position in the blood coagulation cascade. Another coagulation factor, XIa, is also a promising target because its inhibition can suppress thrombosis with a limited contribution to normal hemostasis. In this regard, the development of dual inhibitors as new generation anticoagulants is an urgent problem. Here we report the synthesis and evaluation of novel potential dual inhibitors of coagulation factors Xa and XIa. Based on the principles of molecular design, we selected a series of compounds that combine in their structure fragments of pyrrolo[3,2,1-ij]quinolin-2-one and thiazole, connected through a hydrazine linker. The production of new hybrid molecules was carried out using a two-stage method. The reaction of 5,6-dihydropyrrolo[3,2,1-ij]quinoline-1,2-diones with thiosemicarbazide gave the corresponding hydrazinocarbothioamides. The reaction of the latter with DMAD led to the target methyl 2-(4-oxo-2-(2-(2-oxo-5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1(2H)-ylidene)hydrazineyl)thiazol-5(4H)-ylidene)acetates in high yields. In vitro testing of the synthesized molecules revealed that ten of them showed high inhibition values for both the coagulation factors Xa and XIa, and the IC50 value for some compounds was also assessed. The resulting structures were also tested for their ability to inhibit thrombin.

An Overview of the Structure-Activity Relationship in Novel Antimicrobial Thiazoles Clubbed with Various Heterocycles (2017-2023)

Antimicrobial resistance is an increasing problem for global public health. One of the strategies to combat this issue is the synthesis of novel antimicrobials through rational drug design based on extensive structure-activity relationship studies. The thiazole nucleus is a prominent feature in the structure of many authorized antimicrobials, being clubbed with different heterocycles. The purpose of this review is to study the structure-activity relationship in antimicrobial thiazoles clubbed with various heterocycles, as reported in the literature between 2017 and 2023, in order to offer an overview of the last years in terms of antimicrobial research and provide a helpful instrument for future research in the field.

One-pot synthesis of pyrazolo[4,3-d]thiazole derivatives containing α-aminophosphonate as potential Mur A inhibitors against MDR pathogens with radiosterilization and molecular modeling simulation

The present study involves the synthesis of a new series of α-aminophosphonate derivatives in good yields with a simple workup via the Kabachnik-Fields reaction using lithium perchlorate (LiClO4) as a catalyst to facilitate the reaction. All the newly synthesized compounds were confirmed using various physical, spectroscopic, and analytical data, and the obtained results correlated with the proposed molecular structure. The in vitro antimicrobial activities of each compound were evaluated against different clinical isolates. The results indicated that among these derivatives, two compounds (5a and 5b) were the most active and displayed potent activity with MICs in the range from 0.06 to 0.25 μg mL-1 compared with fosfomycin and fluconazole as standard antibiotics. Moreover, the synthesized phosphonates displayed a broad spectrum of bactericidal and fungicidal activities depending on MICs, MBCs/MFCs, and the time-kill kinetics. In addition, the checkerboard assay showed synergistic and partial synergistic activities between the active compounds combined with fosfomycin and fluconazole. Furthermore, the SEM images showed distinct ruptures of the OM integrity of the FOS-R E. coli at their MICs, which was further indicated by the increased EtBr accumulation within the bacterial cells. Moreover, active derivatives revealed MurA inhibitory activity with IC50 values of 3.8 ± 0.39 and 4.5 ± 0.23 μM compared with fosfomycin (IC50 = 12.7 ± 0.27 μM). To our surprise, exposing 5a and 5b compounds to different gamma radiation doses revealed that 7.0 kGy eradicated the microbial load completely. Finally, the results of quantum chemical study supported the binding mode obtained from the docking study performed inside the active site of MurA (PDB: 1UAE), suggesting that these phosphonates may be promising safe candidates for MDR infection therapy clinical trials with no toxic effects on the normal human cells.

Synthesis, anti-inflammatory activity, inverse molecular docking, and acid dissociation constants of new naphthoquinone-thiazole hybrids

Chronic Inflammation is associated with various types of diseases that involves pro-inflammatory cytokines like IL-6 and TNF-α. High costs and serious side effects of available anti-inflammatory/immunomodulatory drugs led us to design new compounds with promising anti-inflammatory activities. Many drugs and biologically important compounds involve naphthoquinone and thiazole moieties in their core structures. Thereby, here we report the synthesis, characterization and anti-inflammatory activities of new naphthoquinone thiazole hybrids by reaction of naphthoquinone acyl thioureas with various α-bromoketone derivatives. The position of NO2 group in one of the phenyl rings of naphthoquinone thiazole hybrids was changed while different substituents were introduced at the para position of the second phenyl ring. All compounds were tested for potential immunomodulatory effect. No inflammatory cytokines were observed in the absence of LPS stimulant. On the other hand, they had promising anti-inflammatory immunomodulatory activities by being able to decrease the production of the pro-inflammatory cytokines (TNF-α and IL-6) in the LPS-stimulated cells. In an effort to find the possible mechanism of action, several enzymes involved in signalling pathways that play critical roles in inflammatory responses were screened in silico. Subsequent to inverse molecular docking approach, PI3K was predicted be the potential target. The docked complexes of the most potent compounds 5g and 5i were subjected to molecular dynamics simulation to assess the binding stability of the igands with the putative target. Acid dissociation constants (pKa) of the products were also determined potentiometrically.

Design, synthesis and molecular modeling of isatin-aminobenzoic acid hybrids as antibacterial and antibiofilm agents

Number of factors, including newly emerging infectious diseases and an increase in multi-drug resistant microbial pathogens with particular relevance for Gram-positive bacteria, make the treatment of infectious diseases in hospital-based healthcare a major challenge in the medical community. 4-Aminobenzoic acid (PABA), has demonstrated a variety of biological actions particularly, antimicrobial activity. In our study we coupled this vitamin-like molecule with different isatin derivatives. We investigated the antibacterial activity of the synthesized Schiff's bases. The compounds showed high selective activity against Gram-positive bacteria and showed weak or no activity against both Gram-negative bacteria and fungi. Compound 2a showed highest activity against S. aureus and B. subtilis (MIC 0.09 mmol/L). Additionally, these substances exhibit strong anti-B. Subtilis biofilm formation. We were able to shed insight on the binding mode of these new inhibitors using in silico docking of the compounds in the binding sites of a 3D structure of B. subtilis histidine kinase/Walk. The binding free energy of the compound 2a to the catalytic domain walk, of histidine kinase enzyme of B. subtilis bacteria, was calculated using molecular mechanics/generalized born surface area scoring. The key residues for macromolecule-ligand binding were postulated. The optimized 3D protein-ligand binding modes shed light on the B. subtilis HK/Walk-ligand interactions that afford a means to assess binding affinity to design new HK/Walk inhibitor as antibacterial agents.

New Thiophenyl-pyrazolyl-thiazole Hybrids as DHFR Inhibitors: Design, Synthesis, Antimicrobial Evaluation, Molecular Modeling, and Biodistribution Studies

The antibiotic resistance problems constitute a considerable threat to human health worldwide; thus, the discovery of new antimicrobial candidates to conquer this issue is an imperative requirement. From this view, new thiophenyl-pyrazolyl-thiazole hybrids 3-10 were synthesized and screened for their antibacterial efficiency versus Gram - and Gram + bacterial strains compared to the reference drug amoxicillin. It was noticed that the new hybrids displayed significant antibacterial efficacy versus Gram - bacteria, especially against Pseudomonas aeruginosa. Also, all the screened candidates demonstrated a noticeable antifungal effect against Candida albicans (MICs = 3.9-125 μg/mL) relative to fluconazole (MIC = 250 μg/mL). Moreover, the new hybrids were investigated for their antituberculosis potency against Mycobacterium tuberculosis (RCMB 010126). Derivatives 4c, 6b, 8b, 9b, and 10b demonstrated prominent antituberculosis efficiency (MICs = 0.12-1.95 μg/mL) compared with the reference drug isoniazid (MIC = 0.12 μg/mL). The latter derivatives were further assessed for their inhibitory potency versus M. tuberculosis DHFR enzyme. The compounds 4c, 6b and 10b presented a remarkable suppression effect with IC50 values of 4.21, 5.70, and 10.59 μM, respectively, compared to that of trimethoprim (IC50 = 6.23 μM). Furthermore, biodistribution profile using radiolabeling way revealed a perceived uptake of 131I-compound 6b into infection induced models. The docking study for the new hybrids 4c, 6b, 8b, 9b and 10b was performed to illustrate the various binding modes with Mtb DHFR enzyme. In silico ADMET studies for the most potent inhibitors 4c, 6b and 10b were also accomplished to predict their pharmacokinetic and physicochemical features.

Design, green synthesis, and quorum sensing quenching potential of novel 2-oxo-pyridines containing a thiophene/furan scaffold and targeting a LasR gene on P. aeruginosa

The current trend in fighting bacteria is attacking the virulence and quorum-sensing (QS) signals that control bacterial communication and virulence factors, especially biofilm formation. This study reports new Schiff bases and tetracyclic rings based on a pyridine pharmacophore by two methods: a green approach using CAN and a conventional method. The structure of designed derivatives was confirmed using different spectroscopies (IR and 1H/13C NMR) and elemental analysis. The designed derivatives exhibited good to moderate inhibition zones against bacterial and fungal pathogens. In addition, six compounds 2a,b, 3a,b, and 6a,b displayed potency against tested pathogens with eligible MIC and MBC values compared to standard antimicrobial agents. Compound 2a displayed MIC values of 15.6 μg mL-1 compared to Gentamicin (MIC = 250 μg mL-1 against K. pneumoniae), while compound 6b exhibited super-potent activity against P. aeruginosa, and K. pneumoniae with MIC values of 62.5 and 125 μg mL-1, as well as MBC values of 31.25 and 15.6 μg mL-1 compared to Gentamicin (MIC = 250 and 125 μg mL-1 and MBC = 62.5 μg mL-1), respectively. Surprisingly, these six derivatives revealed bactericidal and fungicidal potency and remarkable anti-biofilm activity that could significantly reduce the biofilm formation against MRSA, E. coli, P. aeruginosa, and C. albicans. Furthermore, the most active derivatives reduced the LasR gene's production between 10-40% at 1/8 MICs compared with untreated P. aeruginosa. Besides, they demonstrated promising safety profile on Vero cells (normal cell lines) with IC50 values ranging between (175.17 ± 3.49 to 344.27 ± 3.81 μg mL-1). In addition, the in silico ADMET prediction was carried out and the results revealed that these compounds could be used with oral bioavailability with low toxicity prediction when administered as a candidate drug. Finally, the molecular docking simulation was performed inside LasR and predicted the key binding interactions responsible for the activity that corroborated the biological results.

Unveiling the antitumor potential of novel N-(substituted-phenyl)-8-methoxycoumarin-3-carboxamides as dual inhibitors of VEGFR2 kinase and cytochrome P450 for targeted treatment of hepatocellular carcinoma

Being the sixth most diagnosed cancer and the fourth leading cause of cancer-related deaths worldwide, liver cancer is considered as a serious disease with a high prevalence and poor prognosis. Current anticancer drugs for liver cancer have drawbacks, such as limited efficacy in later stages of the disease, toxicity to healthy cells, and the potential for drug resistance. There is ample evidence that coumarin-based compounds are potent anticancer agents, with numerous analogues currently being investigated in preclinical and clinical studies. The current study aimed to explore the antitumor potency of a new class of 8-methoxycoumarin-3-carboxamides against liver cancer. Toward this aim, we have designed, synthesized, and characterized a new set of N-(substituted-phenyl)-8-methoxycoumarin-3-carboxamide analogues. The assessment of antitumor activity revealed that the synthesized class of compounds possesses substantial cytotoxicity toward Hep-G2 cells when compared to staurosporine, without significant impact on normal cells. Out of the synthesized compounds, compound 7 demonstrated the most potent cytotoxic effect against Hep-G2 cells with an IC50 of 0.75 µM, which was more potent than the drug staurosporine (IC50 = 8.37 µM). The investigation into the mechanism behind the antiproliferative activity of compound 7 revealed that it interferes with DNA replication and induces DNA damage, leading to cell cycle arrest as demonstrated by a significant decrease in the percentage of cells in the G1 and G2/M phases, along with an increase in the percentage of cells in the S phase. Flow cytometric analysis further revealed that compound 7 has the ability to trigger programmed cell death by inducing necrosis and apoptosis in HepG-2 cells. Further explorations into the mechanism of action demonstrated that compound 7 displays a potent dual-inhibitory activity toward cytochrome P450 and vascular endothelial growth factor receptor-2 (VEGFR-2) proteins, as compared to sorafenib drug. Further, detailed computational studies revealed that compound 7 displays a considerable binding affinity toward the binding cavity of VEGFR2 and CYP450 proteins. Taken together, our findings indicate that the newly synthesized class of compounds, particularly compound 7, could serve as a promising scaffold for the development of highly effective anticancer agents against liver cancer.

Synthetic and Semisynthetic Compounds as Antibacterials Targeting Virulence Traits in Resistant Strains: A Narrative Updated Review

This narrative review paper provides an up-to-date overview of the potential of novel synthetic and semisynthetic compounds as antibacterials that target virulence traits in resistant strains. The review focused on research conducted in the last five years and investigated a range of compounds including azoles, indoles, thiophenes, glycopeptides, pleuromutilin derivatives, lactone derivatives, and chalcones. The emergence and spread of antibiotic-resistant bacterial strains is a growing public health concern, and new approaches are urgently needed to combat this threat. One promising approach is to target virulence factors, which are essential for bacterial survival and pathogenesis, but not for bacterial growth. By targeting virulence factors, it may be possible to reduce the severity of bacterial infections without promoting the development of resistance. We discuss the mechanisms of action of the various compounds investigated and their potential as antibacterials. The review highlights the potential of targeting virulence factors as a promising strategy to combat antibiotic resistance and suggests that further research is needed to identify new compounds and optimize their efficacy. The findings of this review suggest that novel synthetic and semisynthetic compounds that target virulence factors have great potential as antibacterials in the fight against antibiotic resistance.

Thiazolyl hydrazineylidenyl indolones as unique potential multitargeting broad-spectrum antimicrobial agents

The emergence of pathogenic and drug-resistant microorganisms seriously threatens public safety. This work constructed a unique type of thiazolyl hydrazineylidenyl indolones (THIs) to combat global microbial multidrug-resistance. Bioactive evaluation discovered that some target THIs displayed much superior antimicrobial efficacy than clinical chloromycetin, norfloxacin, cefdinir or fluconazole against the tested strains. Eminently, butyl THI 6c displayed a broad antimicrobial spectrum with low MICs of 0.25-1 μg/mL. The highly active THI 6c not only showed low cytotoxicity and hemolysis, rapidly bactericidal ability, good antibiofilm activity and promising pharmacokinetic properties, but also could significantly impede the development of bacterial resistance. Preliminary exploration of antibacterial mechanism revealed that THI 6c could effectively penetrate the cell membrane of MRSA and embed DNA to form 6c‒DNA supramolecular complex and thus hinder DNA replication. Moreover, THI 6c could reduce cell metabolic activity, which might be attributed to the fact that THI 6c could target the pyruvate kinase of MRSA and interfere with the function of the enzyme. These results provided powerful information for further developing thiazolyl hydrazineylidenyl indolones as new broad-spectrum antimicrobial agents.

A new class of anti-proliferative activity and apoptotic inducer with molecular docking studies for a novel of 1,3-dithiolo[4,5-b]quinoxaline derivatives hybrid with a sulfonamide moiety

A new series of 6-(pyrrolidin-1-ylsulfonyl)-[1,3]dithiolo[4,5-b]quinoxaline-2-ylidines 10a-f, 12, 14, 16, and 18 were designed, synthesized, and evaluated for their in vitro anticancer activity. The structures of the novel compounds were systematically characterized by 1H NMR, 13C NMR, and elemental analysis. The synthesized derivatives were evaluated for their in vitro antiproliferative activity against three human cancer cell lines (HepG-2, HCT-116, and MCF-7) with more sensitivity to MCF-7. Moreover, three derivatives 10c, 10f, and 12 were the most promising candidates with sub-micromole values. These derivatives were further evaluated against MDA-MB-231, and the results displayed significant IC50 values ranging from 2.26 ± 0.1 to 10.46 ± 0.8 μM and showed low cellular cytotoxicity against WI-38. Surprisingly, the most active derivative 12 revealed sensitivity towards the breast cell lines MCF-7 (IC50 = 3.82 ± 0.2 μM) and MDA-MB-231 (IC50 = 2.26 ± 0.1 μM) compared with doxorubicin (IC50 = 4.17 ± 0.2 and 3.18 ± 0.1 M). Cell cycle analysis showed that compound 12 arrests and inhibits the growth of MCF-7 cells in the S phase with values of 48.16% compared with the untreated control 29.79% and exhibited a significantly higher apoptotic effect in MCF-7 with a value of 42.08% compared to control cell at 1.84%. Furthermore, compound 12 decreased Bcl-2 protein 0.368-fold and activation on pro-apoptotic genes Bax and P53 by 3.97 and 4.97 folds, respectively, in MCF-7 cells. Compound 12 exhibited higher inhibitory activity to EGFRWt, EGFRL858R, and VEGFR-2 with IC50 values (0.19 ± 0.009, 0.026 ± 0.001, and 0.42 ± 0.021 μM) compared with erlotinib (IC50 = 0.037 ± 0.002 and 0.026 ± 0.001 μM) and sorafenib (IC50 = 0.035 ± 0.002 μM). Finally, in silico ADMET prediction presented that 1,3-dithiolo[4,5-b]quinoxaline derivative 12 obeys the Lipinski rule of five and the Veber rule with no PAINs alarms and moderately soluble properties. Additionally, toxicity prediction revealed that compound 12 demonstrated inactivity to hepatotoxic carcinogenicity, immunotoxicity, mutagenicity, and cytotoxicity. Moreover, molecular docking studies showed good binding affinity with lower binding energy inside the active site of Bcl-2 (PDB: 4AQ3), EGFR (PDB: 1M17), and VEGFR (PDB: 4ASD).

Exploring novel derivatives of isatin-based Schiff bases as multi-target agents: design, synthesis, in vitro biological evaluation, and in silico ADMET analysis with molecular modeling simulations

Recently, scientists developed a powerful strategy called "one drug-multiple targets" to discover vital and unique therapies to fight the most challenging diseases. Novel derivatives of isatin-based Schiff bases 2-7 have been synthesized by the reaction of 3-hydrazino-isatin (1) with aryl aldehydes, hetero-aryl aldehydes, and dialdehydes. The structure of the synthesized derivatives was proved by physical and spectral analysis. Additionally, in vitro biological studies were performed, including antioxidant, anti-diabetic, anti-Alzheimer, and anti-arthritic activities. The four derivatives 3b, 5a, 5b, and 5c possess the highest activities. Among the four potent derivatives, compound 5a exhibited the highest antioxidant (TAC = 68.02 ± 0.15 mg gallic acid per g; IRP = 50.39 ± 0.11) and scavenging activities (ABTS = 53.98 ± 0.12% and DPPH = 8.65 ± 0.02 μg mL-1). Furthermore, compound 5a exhibited an α-amylase inhibitory percentage of 57.64 ± 0.13% near the acarbose (ACA = 69.11 ± 0.15%) and displayed inhibitor activity of the acetylcholinesterase (AChE) enzyme = 36.38 ± 0.08%. Moreover, our work extended to determining the anti-arthritic effect, and compound 5a revealed good inhibitor activities with very close values for proteinase denaturation (PDI) = 39.59 ± 0.09% and proteinase inhibition (PI) = 36.39 ± 0.08%, compared to diclofenac sodium PDI = 49.33 ± 0.11% and PI = 41.88 ± 0.09%. Additionally, the quantum chemical calculations, including HOMO, LUMO, and energy band gap were determined, and in silico ADMET properties were predicted, and their probability was recorded. Finally, molecular docking simulations were performed inside α-amylase and acetylcholinesterase enzymes.

Development of novel pyrazole, imidazo[1,2-b]pyrazole, and pyrazolo[1,5-a]pyrimidine derivatives as a new class of COX-2 inhibitors with immunomodulatory potential

Searching for new compounds with anti-inflammatory properties is a significant target since inflammation is a major cause of pain. A series of pyrazole, imidazopyrazolone, and pyrazolopyrimidine derivatives were designed and synthesized by reaction of 3,5-diamino-1H-pyrazole derivative with cyclic and acyclic carbonyl reagents. The structure of the newly synthesized derivatives were fully characterized using different spectroscopic data and elemental analysis, and therefore, evaluated as COX-2 inhibitors. The in vitro COX-2 activity of the tested derivatives 2-13 displayed moderate to good potency with two derivatives 8 and 13 that exhibiting high potency to COX-2 with IC₅₀ values of 5.68 ± 0.08 and 3.37 ± 0.07 μM compared with celecoxib (IC₅₀ = 3.60 ± 0.07 μM) and meloxicam (IC₅₀ = 7.58 ± 0.13 μM). Furthermore, the most active pyrazolo[1,5-a]pyrimidine derivatives 8 and 13 were evaluated to measure the levels of pro-inflammatory proteins such as TNF-α and IL-6 using qRT-PCR in RAW264.7 cells, and the results showed down-regulation of two immunomodulatory proteins. Surprisingly, these derivatives 8 and 13 revealed a decrease in IL-6 level with inhibition percentages of 65.8 and 70.3%, respectively, compared with celecoxib (% = 76.8). Further, compounds 8 and 13 can regulate and suppress the TNF-α with percentage inhibition of 63.1 and 59.2% to controls, while celecoxib displayed an inhibition percentage of 72.7. The Quantum chemical calculation was conducted, and data explained the structural features crucial to the activity. The molecular docking simulation and ADMET predictions revealed that the most active derivatives have good binding affinity, possess appropriate drug-likeness properties and low toxicity profiles. Finally, compounds 8 and 13 demonstrated COX-2 inhibitors with α-TNF and IL-6 suppression capabilities as a dual-action strategy to get more effective treatment.

Development of new spiro[1,3]dithiine-4,11'-indeno[1,2-b]quinoxaline derivatives as S. aureus Sortase A inhibitors and radiosterilization with molecular modeling simulation

Multi-drug resistant microbes have become a severe threat to human health and arise a worldwide concern. A total of fifteen spiro-1,3-dithiinoindenoquinoxaline derivatives 2-7 were synthesized and evaluated for their biological activities against five standard and MDRB pathogens. The MIC and MBC/MFC for the most active derivatives were determined in vitro via broth microdilution assay. These derivatives showed significant activity against the tested strains with microbicidal behavior, with compound 4b as the most active compound (MIC range between 0.06 and 0.25 µg/mL for bacteria strains and MIC = 0.25 µg/mL for C. albicans). The most active spiro-1,3-dithiinoindenoquinoxaline derivatives were able to inhibit the activity of SrtA with IC₅₀ values ranging from 22.15 ± 0.4 µM to 37.12 ± 1.4 µM. In addition, the active spiro-1,3-dithiinoindenoquinoxaline attenuated the in vitro virulence-related phenotype of SrtA by weakening the adherence of S. aureus to fibrinogen and reducing the biofilm formation. Surprisingly, compound 4b revealed potent SrtA inhibitory activity with IC₅₀ = 22.15 µM, inhibiting the adhesion of S. aureus with 39.22 ± 0.15 % compared with untreated 9.43 ± 1.52 %, and showed a reduction in the biofilm biomass of S. aureus with 32.27 ± 0.52 %. We further investigated the effect of gamma radiation as a sterilization method on the microbial load and found that a dose of 5 kGy was sufficient to eradicate the microbial load. The quantum chemical studies exhibited that the tested derivatives have a small energy band gap (ΔE = -2.95 to -3.61 eV) and therefore exert potent bioactivity by interacting with receptors more stabilizing.

Development and radiosterilization of new hydrazono-quinoline hybrids as DNA gyrase and topoisomerase IV inhibitors: Antimicrobial and hemolytic activities against uropathogenic isolates with molecular docking study

This study aimed to synthesize new potent quinoline derivatives based on hydrazone moieties and evaluate their antimicrobial activity. The newly synthesized hydrazono-quinoline derivatives 2, 5a, 9, and 10b showed the highest antimicrobial activity with MIC values ≤1.0 μg/ml against bacteria and ≤8.0 μg/ml against the fungi. Further, these derivatives exhibited bactericidal and fungicidal effects with MBC/MIC and MFC/MIC ratio ≤4. Surprisingly, the most active compounds displayed good inhibition to biofilm formation with MBEC values ranging between (40.0 ± 10.0 - 230.0 ± 31.0) and (67.0 ± 24.0 - 347.0 ± 15.0) μg/ml against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. The hemolytic assays confirmed that the hydrazono-quinoline derivatives are non-toxic with low % lysis values ranging from 4.62% to 14.4% at a 1.0 mg/ml concentration. Besides, compound 5a exhibited the lowest hemolytic activity value of ~4.62%. Furthermore, the study suggests that the hydrazono-quinoline analogs exert their antibacterial activity as dual inhibitors for DNA gyrase and DNA topoisomerase IV enzymes with IC₅₀ values ranging between (4.56 ± 0.3 - 21.67 ± 0.45) and (6.77 ± 0.4 - 20.41 ± 0.32) μM, respectively. Additionally, the recent work advocated that compound 5a showed the reference SAL at the ɣ-radiation dose of 10.0 kGy in the sterilization process without affecting its chemical structure. Finally, the in silico drug-likeness, toxicity properties, and molecular docking simulation were performed. Besides, the result exhibited good oral-bioavailability, lower toxicity prediction, and lower binding energy with good binding mode rather than the positive control.

In vitro enzymatic evaluation of some pyrazolo[1,5-a]pyrimidine derivatives: Design, synthesis, antioxidant, anti-diabetic, anti-Alzheimer, and anti-arthritic activities with molecular modeling simulation

The strategy of utilizing nitrogen compounds in various biological applications has recently emerged as a powerful approach to exploring novel classes of therapeutics to face the challenge of diseases. A series of pyrazolo[1,5-a]pyrimidine-based compounds 3a-l and 5a-f were prepared by the direct cyclo-condensation reaction of 5-amino-1H-pyrazoles 1a, b with 2-(arylidene)malononitriles and 3-(dimethylamino)-1-aryl-prop-2-en-1-ones, respectively. The structures of the new pyrazolo[1,5-a]pyrimidine compounds were confirmed via spectroscopic techniques. The in vitro biological activities of all pyrazolo[1,5-a]pyrimidines 3a-l and 5a-f were evaluated by assaying total antioxidant capacity, iron-reducing power, the scavenging activity against 1-diphenyl-2-picryl-hydrazyl (DPPH) and 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, anti-diabetic, anti-Alzheimer, and anti-arthritic biological activities. All compounds displayed good to potent bioactivity, and three compounds 3g, 3h, and 3l displayed the most active derivatives. Among these derivatives, compound 3l exhibited the highest antioxidant (total antioxidant capacity [TAC] = 83.09 mg gallic acid/g; iron-reducing power [IRP] = 47.93 µg/ml) and free radicals scavenging activities with (DPPH = 18.77 µg/ml; ABTS = 40.44%) compared with ascorbic acid (DPPH = 4.28 µg/ml; ABTS = 38.84%). Furthermore, compound 3l demonstrated the strongest inhibition of α-amylase with a percent inhibition of 72.91 ± 0.14 compared to acarbose = 67.92 ± 0.09%. Similarly, it displayed acetylcholinesterase inhibition of 62.80 ± 0.06%. However, compound 3i showed a significantly higher inhibition percentage for protein denaturation and proteinase at 20.66 ± 0.00 and 26.42 ± 0.06%, respectively. Additionally, some in silico ADMET properties were predicted and studied. Finally, molecular docking simulation was performed inside the active site of α-amylase and acetylcholinesterase to study their interactions.

Discovery of novel pyrazole and pyrazolo[1,5-a]pyrimidine derivatives as cyclooxygenase inhibitors (COX-1 and COX-2) using molecular modeling simulation

Searching for effective and selective anti-inflammatory agents, our study involved designing and synthesizing new pyrazole and pyrazolo[1,5-a]pyrimidine derivatives 4-11. The structures of the synthesized derivatives were confirmed using different spectroscopic techniques. Virtual screening was achieved for the newly designed derivatives using in silico docking simulation inside the active sites of four proteins classified as two cyclooxygenases (COX)-1 (PDB: 3KK6 and 4OIZ) and two COX-2 (PBD: 1CX2 and 3LN1). Among them, six derivatives 4c, 5b, 6a, 7a, 7b, and 10b displayed the highest binding energy. These derivatives were evaluated for their in vitro COX-1 and COX-2 inhibitory activities and their selectivity indexes were calculated. Additionally, these derivatives displayed IC₅₀ values ranging between 4.909 ± 0.25 and 57.53 ± 2.91 µM, and 3.289 ± 0.14 and 124 ± 5.32 µM, against COX-1 and COX-2, respectively. Furthermore, the tested derivatives were found to have selective inhibitory activity on the COX-2 enzyme. Surprisingly, the two pyrazole derivatives 4c and 5b were found to be the most active, with IC₅₀ values of 9.835 ± 0.50 and 4.909 ± 0.25 µM and 4.597 ± 0.20 and 3.289 ±  0.14 µM compared with meloxicam (1.879 ± 0.1 and 5.409 ±  0.23 µM) and celecoxib (5.439 ± 0.28 and 2.164 ± 0.09 µM) against COX-1/-2, respectively. Besides, two pyrazole derivatives, 4c and 5b, displayed a COX-1/COX-2 SI of 2.14 and 1.49. Computational techniques such as molecular docking, density function theory (DFT) calculation, and chemical absorption, distribution, metabolism, excretion, and toxicity evaluation were applied to explain the molecules' binding mode, chemical nature, drug likeness, and toxicity prediction.

Antibiofilm and Anti-Quorum-Sensing Activities of Novel Pyrazole and Pyrazolo[1,5-a]pyrimidine Derivatives as Carbonic Anhydrase I and II Inhibitors: Design, Synthesis, Radiosterilization, and Molecular Docking Studies

Nowadays, searching for new anti-infective agents with diverse mechanisms of action has become necessary. In this study, 16 pyrazole and pyrazolo[1,5-a]pyrimidine derivatives were synthesized and assessed for their preliminary antibacterial and antibiofilm activities. All these derivatives were initially screened for their antibacterial activity against six clinically isolated multidrug resistance by agar well-diffusion and broth microdilution methods. The initial screening presented significant antibacterial activity with a bactericidal effect for five compounds, namely 3a, 5a, 6, 9a, and 10a, compared with Erythromycin and Amikacin. These five derivatives were further evaluated for their antibiofilm activity against both S. aureus and P. aeruginosa, which showed strong biofilm-forming activity at their MICs by >60%. The SEM analysis confirmed the biofilm disruption in the presence of these derivatives. Furthermore, anti-QS activity was observed for the five hybrids at their sub-MICs, as indicated by the visible halo zone. In addition, the presence of the most active derivatives reduces the violacein production by CV026, confirming that these compounds yielded anti-QS activity. Furthermore, these compounds showed strong inhibitory action against human carbonic anhydrase (hCA-I and hCA-II) isoforms with IC50 values ranging between 92.34 and 168.84 nM and between 73.2 and 161.22 nM, respectively. Finally, radiosterilization, ADMET, and a docking simulation were performed.

Evaluation of the anti-proliferative activity of 2-oxo-pyridine and 1′H-spiro-pyridine derivatives as a new class of EGFRWt and VEGFR-2 inhibitors with apoptotic inducers†

Developing new agents for cancer treatment remains a top priority because it is one of the deadliest worldwide. A new series of 2-oxo-pyridine and 1′H-spiro-pyridine derivatives were designed and synthesized based on an N-(ethyl benzoate) moiety. The structure of the designed derivatives was confirmed by different spectroscopic techniques (FT-IR and NMR) and elemental analysis and then evaluated as antiproliferative against HepG-2 and Caco-2 cell lines compared with Doxorubicin. The spiro-pyridine derivatives 5, 7, and 8 exhibited a remarkably higher activity against Caco-2 cell lines than that of other derivatives. Additionally, these derivatives exhibited activation in the Bax and suppressed Bcl-2 expression with variable degrees. Interestingly, compound 7 showed the lowest cytotoxicity value on Caco-2 cells (IC₅₀ = 7.83 ± 0.50 μM) compared with Doxorubicin (IC₅₀ = 12.49 ± 1.10 μM). Additionally, this compound showed activation of the Bax gene (7.508-fold) and suppressed Bcl-2 (0.194-fold) compared to untreated Caco-2 cells, as revealed by the qRT-PCR technique. Moreover, compound 7 could inhibit EGFR and VEGFR-2 with sub-micromole values of 0.124 μM and 0.221 μM compared with Erlotinib (IC₅₀ = 0.033 μM) and Sorafenib (IC₅₀ = 0.043 μM), respectively. Further, cell cycle and apoptosis analysis demonstrated that compound 7 promoted apoptosis by increasing the apoptosis rate from 1.92 to 42.35% and the S cell accumulation ratio from 31.18 to 42.07% compared to untreated Caco-2 cells. Finally, the most active compound 7 showed good drug-likeness and toxicity profiles. Besides, molecular docking studies were performed to determine the binding mode, which is in agreement with the in vitro results.

Design and synthesis a novel of 2-oxo-pyridine and 1′H-spiro-pyridine derivatives as a new apoptotic inducers agents.

Daphnia magna and Gammarus pulex, novel promising agents for biomedical and agricultural applications

Various studies have shown the importance of using different types of Zooplankton biomasses as an additional substance in the diet of fish. In addition, the drainage water of the fish cultures could be used in plant irrigation. In this study, biomasses of water flea Daphnia magna and Gammarus pulex collected and tested, for the first time, their effect against pathogenic microorganisms and on plant germination. The results showed significant antibacterial activity of D. magna and G. pulex against Staphylococcus aureus and Pseudomonas aeruginosa bacteria, as well as antifungal activity against Alternaria solani and Penicillium expansum, which gives the possibility to be used as biocontrol against these bacteria and plant pathogenic fungi. Furthermore, both animals showed positive activity in the germination rate of Vicia faba seed, reaching 83.0 ± 3.5 and 86.0 ± 3.8%, respectively. In conclusion, the biomasses of D. magna and G. pulex are promising and effective agents for their use in the medical field against some pathogenic microbes and as stimulators of plant growth.

A new exploration toward adamantane derivatives as potential anti-MDR agents: Design, synthesis, antimicrobial, and radiosterilization activity as potential topoisomerase IV and DNA gyrase inhibitors

Developing novel antimicrobial agents has become a necessitate due to the increasing rate of microbial resistance to antibiotics. All the newly adamantane derivatives were evaluated for their antimicrobial activities against six MDR clinical pathogenic isolates. The results exhibited that 13 compounds have from potent to good activity. Among those, five derivatives (6, 7, 9, 14a, and 14b) displayed the potent activities against the different isolates tested (MIC < 0.25 µg/ml with bacteria and <8 µg/ml with fungi) compared with Ciprofloxacin (CIP) and Fluconazole (FCA). Additionally, the potent adamantanes showed bactericidal and fungicidal effects based on (MBCs and MFCs) and the time-kill assay. The most active adamantane derivatives 7 and 14b exhibited a synergistic effect of ΣFIC ≤ 0.5 with CIP and FCA against the bacterial and fungal isolates. Moreover, no antagonistic effect appeared for the tested derivatives. Additionally, the interaction of DNA gyrase and topoisomerase IV enzymes with the compounds 6, 7, 9, 14a, and 14b exhibited potent antimicrobial activity using in vitro biochemical assays and gel-based DNA-supercoiling inhibition method. The activity of DNA gyrase and topoisomerase IV enzymes showed inhibitory activity (IC₅₀ ) of 6.20 µM and 9.40 µM with compound 7 and 10.14 µM and 13.28 µM with compound 14b, respectively. Surprisingly, exposing compound 7 to gamma irradiation sterilized and increased its activity. Finally, the in-silico analysis predicted that the most active derivatives had good drug-likeness and safe properties. Besides, molecular docking and quantum chemical studies revealed several important interactions inside the active sites and showed the structural features necessary for activity.

Synthesis, characterization, and in vitro antibacterial activity of some new pyridinone and pyrazole derivatives with some in silico ADME and molecular modeling study

A new series of pyridine-2-one and pyrazole derivatives were designed and synthesized based on cyanoacrylamide derivatives containing 2,4-dichlro aniline and 6-methyl 2-amino pyridine as an aryl group. Condensation of cyanoacrylamide derivatives 3a–d with different active methylene (malononitrile, ethyl cyanoacetate cyanoacetamide, and ethyl acetoacetate) in the presence of piperidine as basic catalyst afforded the corresponding pyridinone derivatives 4a–c, 5, 9, and 13. Furthermore, the reaction of cyanoacrylamide derivatives 3a–d with bi-nucleophile as hydrazine hydrate and thiosemicarbazide afforded the corresponding pyrazole derivatives 14a,b and 16. The newly designed derivatives were confirmed and established based on the elemental analysis and spectra data (IR, 1H NMR, 13C NMR, and mass). The in vitro antibacterial activity was evaluated against four bacterial strains with weak to good antibacterial activity. Moreover, the results indicated that the most active derivatives 3a, 4a, 4b, 9, and 16 might lead to antibacterial agents, especially against B. subtilis and P. vulgaris. The DFT calculations were performed to estimate its geometric structure and electronic properties. In addition, the most active pyridinone and pyrazole derivatives were further evaluated for in silico physicochemical, drug-likeness, and toxicity prediction. These derivatives obeyed all Lipinski’s and Veber’s rules without any violation and displayed non-immunotoxin, non-mutagenic, and non-cytotoxic. Molecular docking simulation was performed inside the active site of Topoisomerase IV (PDB:3FV5). It displayed binding energy ranging from -14.97 kcal/mol to -18.86 kcal/mol with hydrogen bonding and arene–cation interaction. Therefore, these derivatives were suggested to be good antibacterial agents via topoisomerase IV inhibitor.

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Synthesis, characterization, thermal properties, antimicrobial evaluation, ADMET study, and molecular docking simulation of new mono Cu (II) and Zn (II) complexes with 2-oxoindole derivatives

One of the interesting research fields is developing and assessing novel metal-containing medications. A new isatin-3-thiosemicarbazone derivative 4 was synthesized by two different methods based on hydrazone derivatives 2 and 3. Additionally, the chelation of thiosemicarbazone with copper (II) and zinc (II) forms a monobasic tridentate (ONS) complex with two five-member rings and a tetrahedral geometry structure. The structure of synthesized complexes was characterized using elemental analysis, FT-IR, mass spectra, and ¹H/¹³C NMR. Thermogravimetric analysis revealed the upgrading of the thermal stability of metal complexes compared to their thiosemicarbazone ligand. The stoichiometric ratio of the coordination confirmed the formation of 1:1 (M: L) stoichiometry. In vitro antimicrobial activity was screened against two gram-positive, two gram-negative, and one fungal strain. Both ligand 4 and Zn complex 6 displayed high antimicrobial activity compared with copper complex 5 based on the zone of inhibition. Further, MIC and MBC were determined for both zinc and ligand. The zinc complex 6 displayed excellent antimicrobial activity with (MIC = 3.9-27.77 μg/mL) against bacterial strains and (MIC = 7.81 μg/mL) against C. albicans, as well as exhibited MBC values ranging between (MBC = 6.51-45.58 μg/mL) and (MFC = 13.58 μg/mL), respectively, and demonstrated bactericidal and fungicidal behavior. The in-silico ADMET study for ligand and two complexes were determined and showed non-AMES toxicity, non-carcinogenic, and obey the rule of five. A comparative docking study provided more insight into the binding mechanisms and suggested that antimicrobial activity may be due to inhibition of different targets.

One-Pot Synthesis and Molecular Modeling Studies of New Bioactive Spiro-Oxindoles Based on Uracil Derivatives as SARS-CoV-2 Inhibitors Targeting RNA Polymerase and Spike Glycoprotein

The first outbreak in Wuhan, China, in December 2019 was reported about severe acute coronaviral syndrome 2 (SARS-CoV-2). The global coronavirus disease 2019 (COVID-19) pandemic in 2020 resulted in an extremely high potential for dissemination. No drugs are validated in large-scale studies for significant effectiveness in the clinical treatment of COVID-19 patients, despite the worsening trends of COVID-19. This study aims to design a simple and efficient cyclo-condensation reaction of 6-aminouracil derivatives 2a–e and isatin derivatives 1a–c to synthesize spiro-oxindoles 3a–d, 4a–e, and 5a–e. All compounds were tested in vitro against the SARS-CoV-2. Four spiro[indoline-3,5′-pyrido[2,3-d:6,5-d’]dipyrimidine derivatives 3a, 4b, 4d, and 4e showed high activities against the SARS-CoV-2 in plaque reduction assay and were subjected to further RNA-dependent-RNA-polymerase (RdRp) and spike glycoprotein inhibition assay investigations. The four compounds exhibited potent inhibitory activity ranging from 40.23 ± 0.09 to 44.90 ± 0.08 nM and 40.27 ± 0.17 to 44.83 ± 0.16 nM, respectively, when compared with chloroquine as a reference standard, which showed 45 ± 0.02 and 45 ± 0.06 nM against RdRp and spike glycoprotein, respectively. The computational study involving the docking studies of the binding mode inside two proteins ((RdRp) (PDB: 6m71), and (SGp) (PDB: 6VXX)) and geometrical optimization used to generate some molecular parameters were performed for the most active hybrids.

Secondary Metabolites of Actinomycetales as Potent Quorum Sensing Inhibitors Targeting Gram-Positive Pathogens: In Vitro and In Silico Study

Anti-virulence agents are non-bacteriostatic and non-bactericidal emerging therapeutic options which hamper the production of virulence factors in pathogenic flora. In Staphylococcus aureus and Enterococcus faecalis, regulation of virulence genes’ expression occurs through the cyclic peptide-mediated accessory gene regulator (agr) and its ortholog fsr quorum sensing systems, respectively. In the present study, we screened a set of 54 actinomycetales secondary metabolites as novel anti-virulence compounds targeting quorum sensing system of the Gram-positive bacteria. The results indicated that four compounds, Phenalinolactones A–D, BU–4664LMe, 4,5-dehydrogeldamycin, and Questinomycin A, potentially inhibit the agr quorum sensing system and hemolytic activity of S. aureus. On the other hand, Decatromicin A and B, Okilactomycin, Rishirilide A, Abyssomicin I, and Rebeccamycin selectively blocked the fsr quorum sensing system and the gelatinase production in E. faecalis at sub-lethal concentrations. Interestingly, Synerazol uniquely showed the capability to inhibit both fsr and agr quorum sensing systems. Further, in silico molecular docking studies were performed which provided closer insights into the mode of action of these compounds and proposed that the inhibitory activity of these compounds could be attributed to their potential ability to bind to the ATP-active site of S. aureus AgrA. Taken together, our study highlights the potential of actinomycetales secondary metabolites with diverse structures as anti-virulence quorum sensing inhibitors.