Identification of potential inhibitors of Mtb InhA: a pharmacoinformatics approach.

The emergence of superbugs of multi-drug resistant (MDR/RR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (Mtb) strains at a faster rate is posing a serious threat to Tuberculosis (TB) control worldwide. Mtb enoyl-acyl carrier protein reductase (InhA) is a well-established target of the front-line anti-TB prodrug Isoniazid (INH), which requires activation by Catalase-peroxidase enzyme (KatG) in order to inhibit InhA enzyme, that is crucial for the biosynthesis of the mycobacterial cell wall. Currently, due to widespread resistance to this drug, it is necessary to identify new clinical candidates that directly inhibit InhA enzyme and do not require activation by KatG, thereby circumventing most of the resistance mechanisms. In the present study, high-throughput virtual screening of ASINEX database was carried out to identify potential direct inhibitors of Mtb InhA. Best twenty compounds with good binding energies ranging between -12.36 and -9.27 kcal/mol were selected as promising virtual screening hits. These molecules were subjected to ADME study followed by toxicity prediction. Finally, four top-ranked molecules which are structurally diverse and possess best binding affinity than the co-crystalized ligand have been chosen for MD simulation studies followed by MM-GBSA analysis to validate and ensure the stability of hits in the active site of the enzyme. Based on the 100 ns MD simulation studies and binding free energy estimates, three hit molecules B244, B369, and B310 could be considered as potential inhibitors for Mtb InhA, which are likely to be potent against INH-resistant Mtb strains after successful experimental validation.Communicated by Ramaswamy H. Sarma.

Design, Synthesis and Biological Evaluation of New Cycloalkyl Fused Quinolines Tethered to Isatin Schiff Bases as Cholinesterase Inhibitors.

AIMS AND OBJECTIVE: Alzheimer's disease is now a most prevalent neurodegenerative disease of central nervous system leading to dementia in elderly population. Numerous pathological changes have been associated in the progression of Alzheimer's disease. One of such pathological hypotheses is declined cholinergic activity which eventually leads to cognitive and memory deficits. Inhibition o f cholinesterases will apparently elevate acetyl choline levels which is benefactor on cognitive symptoms of the disease. This manuscript describes the new tacrine derivatives tethered to isatin Schiff bases through alkanoyl linker and screened for cholinesterase inhibitory activity. MATERIALS AND METHODS: Tacrine and two more cycloalkyl ring fused quinolones were synthesized and converted to N-cycloalkyl fused quinoline chloroamides. Isatin Schiff bases were also synthesized by the reaction between isatin and substituted aromatic anilines and in subsequent reaction, isatin Schiff bases were reacted with cycloalkyl fused quinolones to afford anticipated compounds 10a-i, 11a-i and 12a-i. All the compounds have been screened for acetyl- and butyrylcholinesterase inhibitory activity and in vivo behavioral studies. Binding interactions of the desired compounds have also been studied by docking them in active site of both cholinesterases. RESULTS: Three compounds 12d, 12e and 12h with propionyl and butyroyl linker between amine and isatin Schiff base scaffold have shown potent acetyl- and butyrylcholinesterase inhibitory activity. However most potent cholinesterase inhibitor was 13d with IC50 value of 0.71±0.004 and 1.08±0.02 µM against acetyl- and butyrylcholinesterases respectively. The hepatotoxicity of potent compounds revealed that the tested compounds were less hepatotoxic than tacrine and also exhibited encouraging in vivo behavioral studies in test animals. Docking studies of all the molecules disclosed close hydrogen bond interactions within the binding site of both cholinesterases. CONCLUSION: New cycloalkyl fused quinolones tethered with alkanoyl linker to isatin Schiff bases endowed significant and potent cholinesterase inhibitory activities. Few of the compounds have also exhibited lesser hepatotoxicity and all the synthesized compounds were good in behavioral studies. Molecular docking studies also indicated close interactions in active site of cholinesterases.

Synthesis, Characterization, Antitubercular and Anti-Inflammatory Activity of New Pyrazolo[3,4-d]Pyrimidines.

AIMS AND OBJECTIVE: Copious proinflammatory cytokines including TNF-α and IL-1ß are involved in progression of inflammation in human body. Inhibition of signaling mediated by proinflammatory cytokines offer effective in the treatment of inflammatory diseases. The treatment of dreadful infectious disease mycobacterium tuberculosis still remains a challenge owing to resistance to multiple drugs hence an urgent need for newer drugs. Pyrazolo[3,4-d]pyrimidines have been disclosed to possess numerous pharmacological activities including anti-inflammatory, antimicrobial and antitubercular activities. Here in we report the synthesis of pyrazolo[3,4-d]pyrimidines for anti-inflammatory and antitubercular activities. MATERIALS AND METHODS: The targeted compounds having pyrazolo[3,4-d]pyrimidine scaffold 8a-m were synthesized in three step reactions with the formation of key intermediate 5-amino-4-- cyno-1-phenyl pyrazole which upon cyclization resulted in 4-amino pyrazolo[3,4-d]pyrimidine for subsequent benzoylation with substituted benzoyl chlorides to form 8a-m. Antiinflammatory activity of 8a-m was assessed at 25 mg/Kg dose and minimum inhibitory concentration against gram positive, gram negative and mycobacteria was also performed. Binding interactions were also measured in binding pocket of p38 kinase. RESULTS: Four compounds 8a, 8b, 8e and 8i significant anti-inflammatory activity in rat paw edema model induced by carrageenan and among all 8b was potent with 80.6% activity. Numerous compounds exhibited potent activity against fungal strains than bacterial strains, compound 8k was most potent against gram negative bacteria Klebsiella pneumoniae. Compounds 8d, 8e and 8f exhibited antitubercular activity with MIC value of 6.25 µg/mL. CONCLUSION: Substituted N-benzoylated amino pyrazolo[3,4-d]pyrimidines endowed significant and potent anti-inflammatory and antimicrobial activities. Molecular docking studies also revealed favorable interactions in active site of p38 kinase.

Pyrazole derivatives as potent inhibitors of c-Jun N-terminal kinase: synthesis and SAR studies.

Mitogen activated protein kinases including c-Jun N-terminal kinase play an indispensable role in inflammatory diseases. Investigation of reported JNK-1 inhibitors indicated that diverse heterocyclic compounds bearing an amide group rendered potent JNK-1 inhibitory activity which prompted us to synthesize new JNK-1 inhibitors containing a pyrazole heterocyclic group. A DABCO mediated 1,3-dipolar cycloaddition reaction in neat resulted in pyrazole carboxylic acid which was converted to desired amides. Upon confirmation of the structures, all the compounds were screened for JNK-1 inhibitory activity and in vivo anti-inflammatory activity. Several synthesized analogues have exhibited JNK-1 inhibitory activity less than 10 µM, in particular compounds 9 c, 10 a and 10 d were found to be potent among all the compounds.

Synthesis, antibacterial, antifungal and antitubercular activities of N-pyrazolylbenzamide derivatives.

A series of new N-pyrazolylbenzamides (5a-x) were synthesized by aroylation of 5-amino-1-phenyl-3-tbutylpyrazole. The structures of synthesized compounds were established based on spectral (FTIR, (1)H NMR, ESI Mass) analysis and purity was ascertained by HPLC. The antibacterial screening revealed that seven molecules exhibited an excellent antibacterial activity and eight compounds demonstrated considerable antifungal activity. Three molecules of the series 5e, 5s and 5w were found to be highly effective against Klebsilla pneumoneia with MIC of 3.12 µg/ml. Compounds 5b, 5f, 5g and 5o exhibited significant antitubercular activity with MIC of 12.5 µg/ml.

Synthesis, p38 kinase inhibitory and anti-inflammatory activity of new substituted benzimidazole derivatives.

P38 mitogen activated protein kinases have been found to involve in the production and release of unwarranted levels of pro-inflammatory cytokines including TNFα and IL-1ß in numerous inflammatory diseases. A new series of molecules, 5-substituted benzoylamino-2-substituted phenylbezimidazoles has been synthesized from 4-nitro-1, 2- diaminobenzene. The synthesized compounds were characterized by FTIR, 1HNMR and Mass. The final compounds were screened for in vitro p38 kinase inhibitory and in vivo anti-inflammatory activity. Three compounds from the series demonstrated nearly 50% inhibition of p38 kinase in the in vitro screening method at 10 µM concentration and two molecules exhibited greater than 75% inhibition of paw oedema volume during the first hour. The docking study of synthesized molecule revealed a new binding pose in ATP binding pocket.

Design, synthesis and characterization of N', N"-diaryl ureas as p38 kinase inhibitors.

Kinases have been known as important molecular targets for various diseases and p38 kinase is found to be vital target among all mitogen activated protein kinases for inflammatory diseases. P38 kinase inhibitors bearing urea scaffold have shown potent kinase inhibitory activity and also selectivity over other kinases. We present here the synthesis, p38 kinase inhibitory and anti-inflammatory activities of compounds containing N', N"-diarylurea scaffold. Compound 7f demonstrated IC50 value of 1.09 µM in p38 kinase assay and 79.41% inhibition of rat paw edema at the 2nd hour of carrageenan challenge. The molecular docking studies of synthesized compounds indicated some of the important hydrogen bonding interactions and also revealed the minor change in the binding pose when compared to BIRB796.

Synthesis of new pyrrolo[2,3-d]pyrimidine derivatives and evaluation of their activities against human colon cancer cell lines.

New pyrrolo[2,3-d]Pyrimidines with heteroaryl substitution at 5th position through sulfur linker were synthesized incorporating putative pharmacophoric moieties like benzimidazole and benzothiazole as heteroaryl groups. Cytotoxic effect of all the compounds was carried out on HCT116 colon cancer cell lines. Compounds 6c and 6h with nitrobenzimidazole and pyrimidyl heterocycles attached at 5th position via sulfur were the most potent of all with IC50 values approximately 17.6 muM. Among the four compounds tested for apoptosis induction activity, 6c induced apoptosis in a dose dependent manner.

Quaternary salts of 4,3' and 4,4' bis-pyridinium monooximes: synthesis and biological activity.

Six unsymmetrical bis-quaternary monooximes viz. dibromides of 1-(4-hydroxyiminomethyl pyridinium)-3-(3/4-carbamoyl pyridinium)propane, 1-(4-hydroxyiminomethyl pyridinium)-4-(3/4-carbamoyl pyridinium) butane, 1-(4-hydroxyiminomethyl pyridinium)-5-(3/4-carbamoyl pyridinium)pentane were synthesized and characterized by spectral data. Their ability to reactivate tetraethyl pyrophosphate inhibited mouse total brain cholinesterase was investigated and compared with 2-pyridine aldoxime chloride (2-PAM). All the compounds were found to be more effective acetylcholinesterase reactivators when compared with the conventional oxime, 2-PAM, except the compound (5a) with pentylene bridge and carbamoyl group present at fourth position. The bis-pyridinium monooximes with 3-carbamoyl group were more potent reactivators than the corresponding 4-carbamoyl compounds and bis-oximes tested.