Novel isoniazid embedded triazole derivatives: Synthesis,antitubercular and antimicrobial activity evaluation

In the present study, a series of new isoniazid embedded triazole derivatives have been synthesized. These compounds were evaluated for their in vitro antitubercular and antimicrobial activities. Among the screened compounds, six have exhibited potent antitubercular activity against Mycobacterium tuberculosis H37Rv strain with MIC value 0.78 μg/mL, whereas, three compounds have displayed activity with MIC value ranging from 1.56 to 3.125 μg/mL. The cytotoxicity of the active compounds was studied against RAW 264.7 cell line by MTT assay and no toxicity was observed even at 25 μg/mL concentration. The five compounds have displayed good antimicrobial activities. Molecular docking have been performed against mycobacterial InhA enzyme to gain an insight into the plausible mechanism of action which could pave the way for our endeavor to identify potent antitubercular candidates. We believe that further optimization of these molecules may lead to potent antitubercular agents.     

Synthesis and evaluation of novel substituted 1,2,3-triazolyldihydroquinolines as promising antitubercular agents

A series of novel substituted 1,2,3-triazolyldihydroquinolines 6a–o was designed and synthesized from 2-acetylthiophene in five-step reaction sequence involving modified Boltzmann-Rahtz reaction of β-Enaminone; Vilsmeier-Haack chloroformylation using DMF/POCl₃; Ohira-Bestmann homologation of aldehyde to alkyne as key steps. The reaction of alkyne 4 with various aryl azides in the presence of copper sulfate and sodium ascorbate resulted desired new 1,2,3-triazolyldihydroquinolines 6a–o in excellent yields. In vitro screening of new compounds for anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv (Mtb), resulted in three derivatives 6a (MIC:1.56?µg/mL) and 6d, 6l (MIC:3.12?µg/mL) as promising antitubercular agents with lower cytotoxicity profiles.     

Synthesis,screening and docking analysis of hispolon analogs as potential antitubercular agents

A series of 20 hispolons/dihydrohispolons were synthesized and characterized by spectral data. These compounds were subjected to in vitro antitubercular activity screening against Mycobacterium tuberculosis (H37Rv) strain. The synthesized compounds showed varied antitubercular activity ranging from 100 to 1.6 μg/mL. Among the screened compounds, four compounds (H1, H2, H3 and H15) have shown moderate activity with MIC 25 μg/mL. Potent activities were observed for the dihydrohispolon derivative H14 (MIC 1.6 μg/mL) followed by H13 (6.25 μg/mL) and H17 (12.5 μg/mL), H19 (3.125 μg/ML). Docking simulations gave good insights on the possible interactions between the tested compounds and β-keto acyl synthase enzyme (mtbFabH). Drug-inhibitor combination studies showed no synergism with the drugs targeting mycolic acid biosynthesis (isoniazid, ethambutol and thiolactomycin, a specific inhibitor of KAS-B enzyme) but showed significant synergism with other drugs including rifampicin and ciprofloxacin ascertaining the drug target for hispolons as inhibition of mycolic acid biosynthesis, probably via mtbFabH.     

Synthesis,cytotoxicity, antimicrobial and anti-biofilm activities of novel pyrazolo[3,4-b]pyridine and pyrimidine functionalized 1,2,3-triazole derivatives

A series of novel pyrazolo[3,4-b]pyridine and pyrimidine functionalized 1,2,3-triazole derivatives 8a–g and 9a–g were prepared starting from 6-trifluoromethylpyridine-2(1H)one 2 via selective O-alkylation, followed by cyclisation using hydrazine hydrate to obtain 6-(trifluoromethyl)-1H-pyrazolo[3,4-b]pyridin-3-amine 4. Compound 4 was diazotized followed by reaction with sodium azide, resulted in 3-azido-6-(trifluoromethyl)-1H-pyrazolo[3,4-b]pyridine 5. Compound 5 was further cyclized with N-/O-propargylated pyrimidine derivatives under Sharpless conditions and obtained compounds 6 and 7, respectively. Each set of compounds 6 and 7 were alkylated with different alkyl halides and obtained respective products 8 and 9. All the products were screened for cytotoxicity against four human cancer cell lines such as A549-Lung (CCL-185), MCF7-Breast (HTB-22), DU145-Prostate (HTB-81) and HeLa-Cervical (CCL-2), compounds 9d, 9e and 9f which showed promising activity have been identified. The products were also screened for antimicrobial, anti bio-film and MBC activities. Promising compounds in each case have been identified.     

Synthesis and in vitro antitubercular activity of ferrocene-based hydrazones

We report here the synthesis and in vitro antitubercular activity of a new series of ferrocenyl derivatives. The quinoline-ferrocene hybrid 5 exhibited significant activity (MIC = 2.5-5 μg/ml) against Mycobacterium tuberculosis. Results indicate that such hybrid compounds provide an efficient approach for future pharmacological developments to fight against tuberculosis. Moreover, the antimalarial drug candidate ferroquine (FQ, SSR97193) was also evaluated mainly because of its structural similarity. FQ was found to display moderate inhibitory activity (MIC = 10-15 μg/ml) against M. tuberculosis. This new drug may offer an interesting alternative in endemic area where malaria and tuberculosis coexist.     

Anti-tubercular agents. Part IV: Synthesis and antimycobacterial evaluation of nitroheterocyclic-based 1,2,4-benzothiadiazines

In continuation of our earlier work on benzothiadiazines, we have prepared a series of nitrofuran, nitrothiophene and arylfuran coupled benzothiadiazines and evaluated them for antimycobacterial and antibacterial activities. One of the compounds 2f has shown good in vitro antimycobacterial activity. All the synthesized compounds have shown moderate to good antibacterial activity.     

Synthesis,evaluation and CoMFA/CoMSIA study of nitrofuranyl methyl N-heterocycles as novel antitubercular agents

A series of novel nitrofuranyl methyl N-heterocycles based on the structure of IIIM-MCD-211 were designed and synthesized. Compounds 6d, 8b and 12a show excellent activity against MTB H37Rv strain (MIC: 0.031–0.062?μg/mL) roughly comparable to INH and IIIM-MCD-211. In addition, a three-dimensional quantitative structure-activity relationship (3D-QSAR) study was performed on the above mentioned chemical series employing comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) techniques. The developed CoMFA and CoMSIA models display high external predictability (r²_pred of 0.954 and 0.935, respectively) and good statistical robustness. More importantly, the newly designed compounds 16a and 16b (MIC: <0.016?μg/mL) based on the two models, as expected, were found to be more active than 12a and IIIM-MCD-21. Design and synthesis of more potent nitrofuranyl methyl N-heterocycles as anti-TB agents are currently in progress.     

Synthesis and biological activity of the nucleoside analogs based on polyfluoroalkyl-substituted 1,2,3-triazoles

This paper offers the results of a synthesis and study of cytotoxicity and the anti-Epstein-Barr virus (EBV) activity of new 2-deoxy-2-chloro-pyranosyl derivatives of 4-tosyl-5-trifluoromethyl-1,2,3-triazole obtained via the addition reaction of the corresponding 2-N-chlorotriazole to the double bond of 3,4,6-tri-O-acetyl-D-glucal. Nucleoside mimetics, derivatives of 4-tosyl-5-polyfluoroalkyl-1,2,3-triazoles containing fragments of 3-chloro-tetrahydrofuran, 3-chloro-tetrahydropyran, tetrahydropyran, dihydrofuran, dihydropyran, or acyclic substituents, were also studied. Evaluation of cytotoxicity (trypan blue and MTT methods) and anti-EBV activity (polymerase chain reaction (PCR) method) showed high selectivity indices for the compounds 4a, 4b, 5b, 6, and 8. A total of 15 novel compounds were examined in this study.     

Studies on molecular properties prediction,antitubercular and antimicrobial activities of novel quinoline based pyrimidine motifs

In the present study, a series of 3-((6-(2,6-dichloroquinolin-3-yl)-4-aryl-1,6-dihydro-pyrimidin-2-yl)thio)propanenitriles 5a–o were synthesized and subjected to molecular properties prediction and drug-likeness model score by Molinspiration property calculation toolkit and MolSoft software, respectively. Compound 5m (4-OCH₃) was found to be maximum drug-likeness model score (0.42). Among the screened compounds, 5m showed the most promising antitubercular activity with MIC of 0.20 μg/mL, while compounds 5g, 5k and 5m displayed broad spectrum antibacterial activity against all the bacterial strains. Moreover, compound 5k was found to be the most potent antifungal agent. Further, the results of preliminary MTT cytotoxicity studies on HeLa cells suggested that potent antimicrobial activity of 5g, 5k and 5m was escorted by low cytotoxicity.     

The bioisosteric modification of pyrazinamide derivatives led to potent antitubercular agents: Synthesis via click approach and molecular docking of pyrazine-1,2,3-triazoles

Tuberculosis remains as a major public health risk which causes the highest mortality rate globally and an improved regimen is required to treat the drug-resistant strains. Pyrazinamide is a first-line antitubercular drug used in combination therapy with other anti-TB drugs. Herein, we describe the modification of pyrazinamide structure using bioisosterism and rational approaches by incorporating the 1,2,3-triazole moiety. Three sets of pyrazine-1,2,3-triazoles (3a-o, 5a-o and 9a-l) are designed, synthesized and evaluated for their in vitro inhibitory potency against mycobacterium tuberculosis H₃₇Rv. The pyrazine-1,2,3-triazoles synthesized through the bioisosteric modification displayed improved activity as compared to rationally modified pyrazine-1,2,3-triazoles. Among 42 title compounds, seven derivatives demonstrated significant anti-tubercular activity with the MIC of 1.56 μg/mL, which are two-fold more potent than the parent compound pyrazinamide. Further, the synthesized pyrazinamide analogs demonstrated moderate inhibition activity against several bacterial strains and possessed an acceptable in vitro cytotoxicity profile as well. Additionally, the activity profile of pyrazine-1,2,3-triazoles was validated by performing the molecular docking studies against the Inh A enzyme. Furthermore, in silico ADME prediction revealed good oral bioavailability for the potent molecules.     

Synthesis and antitubercular activity of substituted phenylmethyl- and pyridylmethyl amines

A total of 42 benzyl- and pyridylmethyl amines were synthesized either by reductive amination of aromatic/heteroaromatic aldehydes with amines or by conjugate addition of amines to the cinnamates followed by reduction of the ester group with lithium aluminium hydride to the respective propanolamines. All the synthesized compounds were evaluated against both avirulent and virulent strains of Mycobacterium tuberculosis. Many of the compounds exhibited MIC as low as 1.56 μg/mL. Few of potent compounds were also evaluated against clinical isolates of MDR TB and found to be active at one or other concentrations with MIC as low as 3.12 μg/mL.     

1,2,3-Triazole-derived naphthalimides as a novel type of potential antimicrobial agents: Synthesis,antimicrobial activity,interaction with calf thymus DNA and human serum albumin

A series of 1,2,3-triazole-derived naphthalimides as a novel type of potential antimicrobial agents were synthesized and characterized by IR, NMR and HRMS spectra. All the new compounds were screened for their antimicrobial activity against four Gram-positive bacteria, four Gram-negative bacteria and three fungi. Bioactive assay manifested that 3,4-dichlorobenzyl compound 9e and its corresponding hydrochloride 11e showed better anti-Escherichia coli activity than Norfloxacin and Chloromycin. Preliminary research revealed that compound 9e could effectively intercalate into calf thymus DNA to form compound 9e–DNA complex which might block DNA replication and thus exert antimicrobial activities. Human serum albumin could effectively store and carry compound 9e by electrostatic interaction.     

Design,synthesis and evaluation of oxime-functionalized nitrofuranylamides as novel antitubercular agents

A series of oxime-functionalized nitrofuranylamides were designed, synthesized and evaluated for their in vitro anti-mycobacterial activities against MTB H37Rv and drug-resistant clinical isolates. Among them, two compounds 7a and 7b exhibited excellent activity against the three tested strains. Both of them were comparable to the first-line anti-TB agents INH and RIF against MTB H37Rv, and were far more potent than INH and RIF against MDR-TB 16833 and 16995 strains. Thus, both of them could act as leads for further optimization.     

Synthesis, antitubercular activity, and SAR study of N-substituted-phenylamino-5-methyl-1H-1,2,3-triazole-4-carbohydrazides

Tuberculosis treatment remains a challenge that requires new antitubercular agents due to the emergence of multidrug-resistant Mycobacterium strains. This paper describes the synthesis, the antitubercular activity and the theoretical analysis of N-substituted-phenylamino-5-methyl-1H-1,2,3-triazole-4-carbohydrazides (8a-b, 8e-f, 8i-j and 8n-o) and new analogues (8c-d, 8g-h, 8l-m and 8p-q). These derivatives were synthesized in good yields and some of them showed a promising antitubercular profile. Interestingly the N-acylhydrazone (NAH) 8n was the most potent against the Mycobacterium tuberculosis H37Rv strain (MIC=2.5 μg/mL) similar to or better than the current drugs on the market. The theoretical structure-activity relationship study suggested that the presence of the furyl ring and the electronegative group (NO(2)) as well as low lipophilicity and small volume group at R position are important structural features for the antitubercular profile of these molecules. NMR spectra, IR spectra and elemental analyses of these substances are reported.     

Synthesis and evaluation of antitubercular activity of glycosyl thio- and sulfonyl acetamide derivatives

A series of glycosyl thioacetamide and glycosyl sulfonyl acetamide derivatives have been prepared following a convenient reaction protocol and evaluated for their antitubercular activity against Mycobacterium tuberculosis H₃₇Rv. Amongst 32 compounds evaluated 3 compounds were effective in inhibiting mycobacterial growth at MIC of 6.25 μg/mL, 6 compounds at MIC of 3.125 μg/mL and 1 compound at MIC of 1.56 μg/mL. All active compounds were found nontoxic in Vero cell lines and mice bone marrow macrophages.     

Design,synthesis, and evaluation of substituted nicotinamide adenine dinucleotide (NAD+) synthetase inhibitors as potential antitubercular agents

Nicotinamide adenine dinucleotide (NAD⁺) synthetase catalyzes the last step in NAD⁺ biosynthesis. Depletion of NAD⁺ is bactericidal for both active and dormant Mycobacterium tuberculosis (Mtb). By inhibiting NAD⁺ synthetase (NadE) from Mtb, we expect to eliminate NAD⁺ production which will result in cell death in both growing and nonreplicating Mtb. NadE inhibitors have been investigated against various pathogens, but few have been tested against Mtb. Here, we report on the expansion of a series of urea-sulfonamides, previously reported by Brouillette et al. Guided by docking studies, substituents on a terminal phenyl ring were varied to understand the structure–activity-relationships of substituents on this position. Compounds were tested as inhibitors of both recombinant Mtb NadE and Mtb whole cells. While the parent compound displayed very weak inhibition against Mtb NadE (IC₅₀ = 1000 µM), we observed up to a 10-fold enhancement in potency after optimization. Replacement of the 3,4-dichloro group on the phenyl ring of the parent compound with 4-nitro yielded 4f, the most potent compound of the series with an IC₅₀ value of 90 µM against Mtb NadE. Our modeling results show that these urea-sulfonamides potentially bind to the intramolecular ammonia tunnel, which transports ammonia from the glutaminase domain to the active site of the enzyme. This hypothesis is supported by data showing that, even when treated with potent inhibitors, NadE catalysis is restored when treated with exogenous ammonia. Most of these compounds also inhibited Mtb cell growth with MIC values of 19–100 µg/mL. These results improve our understanding of the SAR of the urea-sulfonamides, their mechanism of binding to the enzyme, and of Mtb NadE as a potential antitubercular drug target.     

Synthesis and biological evaluation of some novel N-aryl-1,4-dihydropyridines as potential antitubercular agents

1,4-Dihydropyridines are the emerging class of antitubercular agent. Recently, studies have revealed that 1,4-dihydropyridine-3,5-dicarbamoyl derivatives with lipophilic groups have demonstrated excellent antitubercular activity. We have synthesized new N-aryl-1,4-dihydropyridines bearing carbethoxy and acetyl group at C-3 and C-5 of the DHP ring. In addition, 1H-pyrazole ring is substituted at C-4 position. The lowest minimum inhibitory concentration value, 0.02 μg/mL, was found for diethyl 1-(2-chlorophenyl)-1,4-dihydro-2,6-dimethyl-4-(1,3-diphenyl-1H-pyrazol-4-yl)pyridine-3,5-dicarboxylate 4e making it more potent than first line antitubercular drug isoniazid. In addition, this compound exhibited relatively low cytotoxicity.     

Synthesis,antitumor activity,and cytotoxicity of 4-substituted 1-benzyl-5-diphenylstibano-1H-1,2,3-triazoles

Trisubstituted 5-organostibano-1H-1,2,3-triazoles (3a–f) were synthesized by the Cu-catalyzed azide-alkyne cycloaddition of various ethynylstibanes (1) with benzylazide (2) in the presence of CuBr (5 mol%) under aerobic conditions. The reaction of 5-stibanotriazoles with HCl afforded C5-unsubstituted 1,2,3-triazoles (4a–f). The antitumor activity of trisubstituted 5-organostibano-1H-1,2,3-triazoles (3a–f) and their 5-unsubstituted 1,2,3-triazoles (4a–f) were evaluated in several tumor cell lines. All 5-stibanotriazoles (3a–f) exerted an excellent antitumor activity. On the contrary, 5-unsubstituted 1,2,3-triazoles (4a–f) without a diphenylantimony group in the molecule exhibited very low antitumor activity compared with 5-stibanotriazoles (3a–f). In compounds of both the series, the substituted 4-butyl group appeared to decrease antitumor activity. However, results suggested that organometal (antimony) in the molecule was required for greater antitumor activity. In addition, all 5-stibanotriazoles (3a–f), but not all 5-unsubstituted 1,2,3-triazoles (4a–f), exhibited cytotoxicity in normal vascular endothelial cells derived from bovine aorta. Among the compounds (3b–e) that exhibited excellent antitumor activity, those with 4-methylphenyl (3b) and 1-cyclohexenyl (3e) showed relatively low cytotoxicity to vascular endothelial cells. Together, these results suggest that trisubstituted 5-organostibano-1H-1,2,3-triazoles, including compounds 3b and 3e, may serve as potential anticancer therapeutic drugs in the future.     

Molecular properties prediction and synthesis of novel 1,3,4-oxadiazole analogues as potent antimicrobial and antitubercular agents

In the present investigation, a series of 1,5-dimethyl-2-phenyl-4-{[(5-aryl-1,3,4-oxadiazol-2-yl)methyl]amino}-1,2-dihydro-3H-pyrazol-3-one were subjected to molecular properties prediction, drug-likeness by Molinspiration (Molinspiration, 2008) and MolSoft (MolSoft, 2007) software, lipophilicity and solubility parameters using ALOGPS 2.1 program. The compounds followed the Lipinski ‘Rule of five’ were synthesized for antimicrobial and antitubercular screening as oral bioavailable drugs/leads. Maximum drug-likeness model score (0.95) was found for compound, 4a. All the synthesized compounds were characterized by IR, NMR and mass spectral analysis followed by antimicrobial and antimycobacterial screening. Among the title compounds, compound 4d showed pronounced activity against Mycobacterium tuberculosis H₃₇Rv and isoniazid resistant M. tuberculosis (INHR-TB) with minimum inhibitory concentrations (MICs) 0.78 μM and 1.52 μM, respectively. The compound, 4a showed maximum activity against all bacterial strains with MIC 4–8 μg/mL comparable to standard drug ciprofloxacin, while the compounds, 4e and 4k showed maximum antifungal activity with MIC 8–16 μg/mL less active than standard drug fluconazole.     

Synthesis, molecular modeling and bio-evaluation of cycloalkyl fused 2-aminopyrimidines as antitubercular and antidiabetic agents

An economical and efficient one step synthesis of a series of 8-(arylidene)-4-(aryl)-5,6,7,8-tetrahydro-quinazolin-2-ylamines and 9-(arylidene)-4-(aryl)-6,7,8,9-tetrahydro-5H-cycloheptapyrimidin-2-ylamines by the reaction of bis-benzylidene cycloalkanones and guanidine hydrochloride in presence of NaH has been developed. All the synthesized compounds were evaluated against Mycobacterium tuberculosis H₃₇Rv strain and the α-glucosidase and glycogen phosphorylase enzymes. Few of the compounds have shown interesting in vitro activity with MIC up to 3.12 μg/mL against M. tuberculosis and very good inhibition of α-glucosidase and glycogen phosphorylase enzymes. The most potent non toxic compound 40 exhibited about 58% ex vivo activity at MIC of 3.12 μg/mL. The present study opens a new gate to synthesize antitubercular agents for diabetic TB patients. In silico docking studies indicate that mycobacterial dihydrofolate reductase is the possible target of these compounds.