Design,Synthesis, Antibacterial Evaluation and Docking Study of Novel 2‐Hydroxy‐3‐(nitroimidazolyl)‐propyl‐derived Quinolone

A novel series of 2‐hydroxy‐3‐(nitroimidazolyl)‐propyl‐derived quinolones 6a – o were synthesized and evaluated for their in vitro antibacterial activity. Most of the target compounds exhibited potent activity against Gram‐positive strains. Among them, moxifloxacin analog 6n displayed the most potent activity against Gram‐positive strains including S. epidermidis (MIC = 0.06 μg/mL), MSSE (MIC = 0.125 μg/mL), MRSE (MIC = 0.03 μg/mL), S. aureus (MIC = 0.125 μg/mL), MSSA (MIC = 0.125 μg/mL), (MIC = 2 μg/mL). Its activity against MRSA was eightfold more potent than reference drug gatifloxacin. Finally, docking study of the target compound 6n revealed that the binding model of quinolone nucleus was similar to that of gatifloxacin and the 2‐hydroxy‐3‐(nitroimidazolyl)‐propyl group formed two additional hydrogen bonds.     

Exploration of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazoles as selective,multitargeted antimycobacterial agents

We report the biological evaluation of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazole derivatives against bacteria, eukaryotic cell lines and the assessment of their mechanisms of action to determine their prospects of being developed into potent antituberculosis agents. The compounds were evaluated for their antibacterial property against Mycobacterium tuberculosis H37Rv, multidrug‐resistant M. tuberculosis, Mycobacterium bovis BCG, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus using high‐throughput spot‐culture growth inhibition assay. They were found to be selective toward slow‐growing mycobacteria and Gram‐positive bacteria. In M. bovis BCG, they exhibited a bactericidal mode of action. Cytotoxicity was assessed in human THP‐1 and murine RAW 264.7 cell lines, and the compounds showed a lower cytotoxicity potential when compared with their antibacterial activity. They were found to be excellent whole‐cell efflux pump inhibitors of the mycobacterial surrogate M. aurum, performing better than known efflux pump inhibitor verapamil. The 5‐nitrothiophene moiety was identified for the first time as a prospective inhibitor scaffold of mycobacterial arylamine N‐acetyltransferase enzyme, which is the key enzyme in metabolizing isoniazid, a first‐line antituberculosis drug. The two aforementioned findings make the compounds potential hits in the development of adjunctive tuberculosis therapy.     

Design,synthesis and biological evaluation of novel quinoline‐based carboxylic hydrazides as anti‐tubercular agents

In this study, seventeen novel quinoline‐based carboxylic hydrazides were designed as potential anti‐tubercular agents using molecular hybridization approach and evaluated in‐silico for drug‐likeness behavior. The compounds were synthesized, purified, and characterized using spectral techniques (like FTIR, ¹H NMR, and Mass). The in‐vitro anti‐tubercular activity (against Mycobacterium tuberculosisH37Ra) and cytotoxicity against human lung fibroblast cells were studied. Among the tested hydrazides, four compounds ( 6h , 6j , 6l, and 6m ) exhibited significant anti‐tubercular activity with MIC values below 20 μg/mL. The two most potent compounds of the series, 6j and 6m exhibited MIC values 7.70 and 7.13 μg/mL, respectively, against M. tuberculosis with selectivity index >26. Structure–activity relationship studies were performed for the tested compounds in order to explore the effect of substitution pattern on the anti‐tubercular activity of the synthesized compounds.     

Synthesis,biological evaluation,and molecular docking studies of novel 3‐aryl‐5‐(alkyl‐thio)‐1H‐1,2,4‐triazoles derivatives targeting Mycobacterium tuberculosis

A small library of new 3‐aryl‐5‐(alkyl‐thio)‐1H‐1,2,4‐triazoles was synthesized and screened for the antimycobacterial potency against Mycobacterium tuberculosis H₃₇Ra strain and Mycobacterium bovis BCG both in active and dormant stage. Among the synthesized library, 25 compounds exhibited promising anti‐TB activity in the range of IC₅₀0.03–5.88 μg/ml for dormant stage and 20 compounds in the range of 0.03–6.96 μg/ml for active stage. Their lower toxicity (>100 μg/ml) and higher selectivity (SI = >10) against all cancer cell lines screened make them interesting compounds with potential antimycobacterial effects. Furthermore, to rationalize the observed biological activity data and to establish a structural basis for inhibition of M. tuberculosis, the molecular docking study was carried out against a potential target MTB CYP121 which revealed a significant correlation between the binding score and biological activity for these compounds. Cytotoxicity and in vivo pharmacokinetic studies suggested that 1,2,4‐triazole analogues have an acceptable safety index, in vivo stability and bio‐availability.     

Design,synthesis, and in vitro antimicrobial activity of hydrazide–hydrazones of 2‐substituted acetic acid

In this study, 30 hydrazide–hydrazones of phenylacetic ( 3 – 10 ) and hydroxyacetic acid ( 11 – 32 ) were synthesized by the condensation reaction of appropriate 2‐substituted acetic acid hydrazide with different aromatic aldehydes. The obtained compounds were characterized by spectral data and evaluated in vitro for their potential antimicrobial activities against a panel of reference strains of micro‐organisms, including Gram‐positive bacteria, Gram‐negative bacteria, and fungi belonging to the Candida spp. The results from our antimicrobial assays indicated that among synthesized compounds 3 – 32 , especially compounds 6 , 14, and 26 showed high bactericidal activity (MIC = 0.488–7.81 μg/ml) against reference Gram‐positive bacteria, and in some cases, their activity was even better than that of commonly used antibiotics, such as cefuroxime or ampicillin.     

2‐Aryl‐3‐(1H‐Azol‐1‐yl)‐1H‐Indole Derivatives: A New Class of Antimycobacterial Compounds – Conventional Heating in Comparison with MW‐Assisted Synthesis

2‐Aryl‐3‐(1H‐imidazol‐1‐yl and 1H‐1,2,4‐triazol‐1‐yl)‐1H‐indole derivatives were synthesized and tested for their in‐vitro antifungal and antimycobacterial activities. These indole derivatives were devoid of antifungal activity against the tested strains of Candida spp. Yet, they exhibited an interesting antitubercular activity against Mycobacterium tuberculosis reference strain H₃₇Rv.     

Synthesis and mycobacterial evaluation of 5‐substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido‐[2,3‐d]pyrimidin‐4(3H)‐one derivatives

5‐Substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido[2,3‐d]pyrimidin‐4(3H)‐one derivatives were synthesized and evaluated against Mycobacterium tuberculosis H37Rv, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus as well as a human monocyte‐derived macrophage (THP‐1), and murine macrophage (RAW 264.7) cell lines to assess their antibacterial and cytotoxic potential, respectively. The compounds showed activity in the range of 1.95–125 µg/ml against M. tuberculosis but showed no activity against M. aurum, E. coli, and S. aureus, indicating selectivity towards slow‐growing mycobacterial pathogens. The compounds exhibited very low to no cytotoxicity up to 500 µg/ml concentration against eukaryotic cell lines. The most potent molecule, 2l , showed a minimum inhibitory concentration of 1.95 µg/ml against M. tuberculosis H37Rv and a selectivity index of >250 against both the eukaryotic cell lines. Furthermore, 2l showed moderate inhibition of whole‐cell mycobacterial drug‐efflux pumps when compared to verapamil, a known potent inhibitor of efflux pumps. Thus, derivative 2l was identified as an antituberculosis hit molecule, which could be used to yield more potent lead molecules.     

Design,Synthesis, and in vitro antitubercular activity of 1,2,3‐triazolyl‐dihydroquinoline derivatives

In the quest for new active molecules against Mycobacterium tuberculosis, a series of dihydroquinoline derivatives possessing triazolo substituents were efficiently synthesized using click chemistry. The structure of 6l was evidenced by X‐ray crystallographic study. The newly synthesized compounds were evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv (ATCC27294). The compounds 6a , 6g, and 6j (MIC: 3.13 μg/ml) showed promising activity when compared to the first‐line drug such as ethambutol. In addition, the structure and antitubercular activity relationship were further supported by in silico molecular docking studies of the active compounds against 3IVX.PDB (crystal structure of pantothenate synthetase in complex with 2‐(2‐(benzofuran‐2‐ylsulfonylcarbamoyl)‐5‐methoxy‐1H‐indol‐1‐yl)acetic acid).     

A Facile One‐Pot Synthesis of 2‐Arylamino‐5‐Aryloxylalkyl‐1,3,4‐Oxadiazoles and Their Urease Inhibition Studies

A one‐pot method for the synthesis of structural type urease inhibitors, 2‐amino‐1,3,4‐oxadiazoles, was developed. The structures of the compounds were established using spectroanalytical techniques and unambiguously confirmed by single‐crystal X‐ray analysis of compound 3o . The synthesized compounds were tested against jack beans urease, and most of the compounds ( 3c , 3g , 3j , 3k , 3n , 3r – 3v ) were found more active than the standard. The most potent compound ( 3u ) had an IC₅₀ value of 6.03 ± 0.02 μm as compared to the IC₅₀ value of the standard (thiourea; 22.0 ± 1.2 μm ). The prominent urease inhibition activity of these compounds may serve as an important finding in the development of less toxic and more potent antiulcer drugs. The compounds were also investigated against four bacterial strains, and some of the compounds ( 3g and 3r ) were found more potent than the standard drug (ciprofloxacin) against all the tested strains. The MIC value for compound 3g was 0.156 μmol/mL against the tested bacterial strains.     

Design,synthesis, and in vitro antituberculosis activity of benzo[6,7]cyclohepta[1,2‐b]pyridine‐1,3,4‐oxadiazole derivatives

A new antitubercular agents, benzo[6,7]cyclohepta[1,2‐b]pyridine‐1,3,4‐ oxadiazole hybrids ( 6a–o ), have been designed and synthesized involving oxidative cyclization of hydrazones by use of di(acetoxy)iodobenzene, characterized by IR,¹H NMR,¹³C NMR, and HRMS, and further confirmed by X‐ray analysis. All the newly synthesized compounds 4a–o evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (ATCC27294). Among the compounds tested, the compounds 4o (MIC: 1.56  μg/ml) and 4l, 4m (MIC: 3.125  μg/ml) are promising lead analogues and have shown lower cytotoxicity.     

Synthesis and biological evaluation of 1,2,4‐triazole‐3‐thione and 1,3,4‐oxadiazole‐2‐thione as antimycobacterial agents

Resistance among dormant mycobacteria leading to multidrug‐resistant and extremely drug‐resistant tuberculosis is one of the major threats. Hence, a series of 1,2,4‐triazole‐3‐thione and 1,3,4‐oxadiazole‐2‐thione derivatives ( 4a–5c ) have been synthesized and screened for their antitubercular activity against Mycobacterium tuberculosis H37Ra (H37Ra). The triazolethiones 4b and 4v showed high antitubercular activity (both MIC and IC₅₀) against the dormant H37Ra by in vitro and ex vivo. They were shown to have more specificity toward mycobacteria than other Gram‐negative and Gram‐positive pathogenic bacteria. The cytotoxicity was almost insignificant up to 100 μg/ml against THP‐1, A549, and PANC‐1 human cancer cell lines, and solubility was high in aqueous solution, indicating the potential of developing these compounds further as novel therapeutics against tuberculosis infection.     

Design and synthesis of 9H‐fluorenone based 1,2,3‐triazole analogues as Mycobacterium tuberculosis InhA inhibitors

We prepared fifty various 9H‐fluorenone based 1,2,3‐triazole analogues varied with NH, –S–, and –SO₂– groups using click chemistry. The target compounds were characterized by routine analytical techniques, ¹H, ¹³CNMR, mass, elemental, single‐crystal XRD ( 8a ) and screened for in vitro antitubercular activity against Mycobacterium tuberculosis (MTB) H37Rv strain and two “wild” strains Spec. 210 and Spec. 192 and MIC₅₀ was determined. Further, the compounds were evaluated for MTB InhA inhibition study as well. The final analogues exhibited minimum inhibitory concentration (MIC) ranging from 52.35 to >295 μm . Among the –NH– analogues, one compound 5p (MIC 58.34 μm ), among –S– containing analogues four compounds 8e (MIC 66.94 μm ), 8f (MIC 74.20 μm ), 8g (MIC 57.55 μm ), and 8q (MIC 56.11 μm ), among –SO₂– containing compounds one compound 10p (MIC 52.35 μm ) showed less than MTB MIC 74.20 μm : Compound 4‐(((9H‐fluoren‐9‐yl)sulfonyl)methyl)‐1‐(3,4,5‐trimethoxyphenyl)‐1H‐1,2,3‐triazole ( 10p ) was found to be the most active compound with 73% InhA inhibition at 50 μm ; it inhibited MTB with MIC 52.35 μm . Further, 10f and 10p were docked to crystal structure of InhA to know binding interaction pattern. Most active compounds were found to be non‐cytotoxic against HEK 293 cell lines at 50 μm .     

Design,synthesis and pharmacophoric model building of new 3‐alkoxymethyl/3‐phenyl indole‐2‐carboxamides with potential antiproliferative activity

Novel 3‐alkoxymethyl/3‐phenyl indole‐2‐carboxamide derivatives were synthesized and evaluated for their anticancer activity. Most of the tested compounds showed moderate to excellent activity against the tested cell lines (MCF7 and HCT116). 3‐Phenyl substitution on indole with p‐piperidinyl phenethyl 24a and p‐dimethylamino phenethyl 24c exhibited anticancer activity against MCF7 with IC₅₀ of 0.13 and 0.14 μm , respectively. Further mechanistic study of the most active compounds through their action on cell cycle showed disturbance in cell cycle progression and cell cycle arrest. For future development of this series of compounds, pharmacophore study was conducted which indicated that the enhancement of the activity could be achieved through the addition of acceptor or donating groups to the already‐present indole nucleus.     

Synthesis and Antimicrobial Activity of the Hybrid Molecules between Sulfonamides and Active Antimicrobial Pleuromutilin Derivative

A series of novel hybrid molecules between sulfonamides and active antimicrobial 14‐o‐(3‐carboxy‐phenylsulfide)‐mutilin were synthesized, and their in vitro antibacterial activities were evaluated by the broth microdilution. Results indicated that these compounds displayed potent antimicrobial activities in vitro against various drug‐susceptible and drug‐resistant Gram‐positive bacteria such as Staphylococci and streptococci, including methicillin‐resistant Staphylococcus aureus, and mycoplasma. In particular, sulfapyridine analog ( 6c ) exhibited more potent inhibitory activity against Gram‐positive bacteria and mycoplasma, including Staphylococcus aureus (MIC = 0.016–0.063 μg/mL), methicillin‐resistant Staphylococcus aureus (MIC = 0.016 μg/mL), Streptococcus pneumoniae (MIC = 0.032–0.063 μg/mL), Mycoplasma gallisepticum (MIC = 0.004 μg/mL), with respect to other synthesized compounds and reference drugs sulfonamide (MIC = 8–128 μg/mL) and valnemulin (MIC = 0.004–0.5 μg/mL). Furthermore, comparison between MIC values of pleuromutilin‐sulfonamide hybrids 6a–f with pleuromutilin parent compound 3 revealed that these modifications at 14 position side chain of the pleuromutilin with benzene sulfonamide could greatly improve the antibacterial activity especially against Gram‐positives.     

5‐Arylaminouracil Derivatives: New Inhibitors of Mycobacterium tuberculosis

Three series of 5‐arylaminouracil derivatives, including 5‐(phenylamino)uracils, 1‐(4′‐hydroxy‐2′‐cyclopenten‐1′‐yl)‐5‐(phenylamino)uracils, and 1,3‐di‐(4′‐hydroxy‐2′‐cyclopenten‐1′‐yl)‐5‐(phenylamino)uracils, were synthesized and screened for potential antimicrobial activity. Most of compounds had a negative effect on the growth of the Mycobacterium tuberculosis H37Rv strain, with 100% inhibition observed at concentrations between 5 and 40 μg/mL. Of those, 1‐(4′‐hydroxy‐2′‐cyclopenten‐1′‐yl)‐3‐(4?‐hydroxy‐2?‐cyclopenten‐1?‐yl)‐5‐(4″‐butyloxyphenylamino)uracil proved to be the most active among tested compounds against the M. tuberculosis multidrug‐resistant strain MS‐115 (MIC₉₀ 5 μg/mL). In addition, the thymidylate kinase of M. tuberculosis was evaluated as a possible enzymatic target.     

Synthesis of new bis‐pyrazole linked hydrazides and their in vitro evaluation as antimicrobial and anti‐biofilm agents: A mechanistic role on ergosterol biosynthesis inhibition in Candida albicans

Literature reports suggest that pyrazoles and hydrazides are potential antimicrobial pharmocophores. Considering this fact, a series of nineteen conjugates containing hybrids of bis‐pyrazole scaffolds joined through a hydrazide linker were synthesized and further evaluated for their antimicrobial activity against a panel of Gram‐positive and Gram‐negative bacteria along with Candida albicansMTCC 3017 strain. Although the derivatives exhibited good antibacterial activity, some of the derivatives ( 13d , 13j , 13l , 13p , and 13r ) showed excellent anti‐Candida activity with MICs values of 3.9 μg/ml, which was equipotent to that of the standard Miconazole (3.9 μg/ml), which has inspired us to further explore their anti‐Candida activity. The same compounds were also tested for anti‐biofilm studies against various Candida strains and among them, compounds 13l and 13r efficiently inhibited the formation of fungal biofilms. Field emission scanning electron micrographs revealed that one of the promising compound 13r showed cell damage and in turn cell death of the Candida strain. These potential conjugates ( 13l and 13r ) also demonstrated promising ergosterol biosynthesis inhibition against some of the strains C. albicans, which were further validated through molecular docking studies. In silico computational studies were carried out to predict the binding modes and pharmacokinetic parameters of these conjugates.     

Design,Synthesis, and Biological Evaluation of 1,4‐dihydropyridine Derivatives as Potent Antitubercular Agents

A series of novel 1,4‐dihydropyridine‐3,5‐dicarbamoyl derivatives bearing an imidazole nucleus at C‐4 position were synthesized in excellent yields via multicomponent Hantzsch reaction. The newly synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectroscopy. The synthesized compounds 3a‐p were screened for antitubercular activity. Among all the screened compounds, compounds 3j and 3m showed most prominent activity against Mycobacterium tuberculosis with minimum inhibitory concentration of 0.02 μg/mL and SI > 500, making it more potent than first‐line antitubercular drug isoniazid. In addition, these compounds displayed relatively low cytotoxicity.     

Design and synthesis of 4′‐((5‐benzylidene‐2,4‐dioxothiazolidin‐3‐yl)methyl)biphenyl‐2‐carbonitrile analogs as bacterial peptide deformylase inhibitors

Herein, we report the synthesis and screening of 4′‐((5‐benzylidene‐2,4‐dioxothiazolidin‐3‐yl)methyl)biphenyl‐2‐carbonitrile analogs 11(a–j) as bacterial peptide deformylase (PDF) enzyme inhibitors. The compounds 11b (IC₅₀ value = 139.28 μm ), 11g (IC₅₀ value = 136.18 μm ), and 11h (IC₅₀ value = 131.65 μm ) had shown good PDF inhibition activity. The compounds 11b (MIC range = 103.36–167.26 μg/mL), 11g (MIC range = 93.75–145.67 μg/mL), and 11h (MIC range = 63.61–126.63 μg/mL) had also shown potent antibacterial activity when compared with standard ampicillin (MIC range = 100.00–250.00 μg/mL). Thus, the active derivatives were not only PDF inhibitors but also efficient antibacterial agents. To gain more insight on the binding mode of the compounds with PDF enzyme, the synthesized compounds 11(a–j) were docked against PDF enzyme of Escherichia coli and compounds exhibited good binding properties. The results suggest that this class of compounds has potential for development and use in future as antibacterial drugs.     

N‐Benzylsalicylthioamides: Highly Active Potential Antituberculotics

A gseries of 29 new derivatives of N‐benzylsalicylthioamides was synthesized and the compounds were tested for in‐vitro antimycobacterial activity against Mycobacterium tuberculosis, Mycobacterium kansasii, and Mycobacterium avium. The activity was analyzed by quantitative structure‐activity relationship (QSAR). Activity increased with increasing lipophilicity and electron donating effect of the substituents in the acyl moiety and decreased with the electrophilic superdelocalizability of the molecules. The most active compounds are more active than isoniazid (INH) and are active against INH‐resistant potential pathogenic strains of mycobacterium.     

Metronidazole containing pyrazole derivatives potently inhibit tyrosyl‐tRNA synthetase: design,synthesis, and biological evaluation

As an important enzyme in bacterial protein biosynthesis, tyrosyl‐tRNA synthetase (TyrRS) has been an absorbing therapeutic target for exploring novel antibacterial agents. A series of metronidazole‐based antibacterial agents has been synthesized and identified as TyrRS inhibitors with low cytotoxicity and significant antibacterial activity, especially against Gram‐negative organisms. Of the compounds obtained, 4f is the most potent agent which inhibited the growth of Pseudomonas aeruginosa ATCC 13525 (MIC = 0.98 μg/mL) and exhibited TryRS inhibitory activity (IC₅₀ = 0.92 μm ). Docking simulation was performed to further understand its potency. Membrane‐mediated apoptosis in P. aeruginosa was verified by flow cytometry.