Professionally a medical biochemist with almost a decade of experience as a bench scientist in the field of antibacterial drug discovery and method development for HTS. Rich experience in protein and DNA biochemistry with technical expertise in molecular biology & biophysical techniques.
Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the deve... more Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the development of new antibacterial agents that are impacted by target-mediated cross resistance with fluoroquinolones. The present study demonstrates the successful synthesis and evaluation of bisbenzimidazole analogues as Escherichia coli topoisomerase IA inhibitors. 5-(4-Propylpiperazin-1-yl)-2-[2'-(4-ethoxyphenyl)-5'-benzimidazolyl]benzimidazole (12b) showed significant relaxation inhibition activity against EcTopo 1A (IC50 = 2 ± 0.005 μM) and a tendency to chelate metal ion. Interestingly, these compounds did not show significant inhibition of E. coli DNA gyrase and hTop 1 even up to 100 μM. Compound 12b has shown lowest MIC against E. coli strains among 24 compounds evaluated. The binding affinity constant and binding free energy of 12b with EcTopo 1A was observed 6.8 × 10(6) M(-1) and -10.84 kcal mol(-1) from isothermal titration calorimetry (ITC), respectively. In vivo mouse systemic infection and neutropenic thigh model experimental results confirmed the therapeutic efficacy of 12b, suggesting further development of this class of compounds as antibacterial agents.
Topoisomerases are proven drug targets, but antibiotics that poison bacterial Topoisomerase 1 (To... more Topoisomerases are proven drug targets, but antibiotics that poison bacterial Topoisomerase 1 (Top1) have yet to be discovered. We have developed a rapid and direct assay for quantification of Top1-DNA adducts that is suitable for high throughput assays. Adducts are recovered by “RADAR fractionation”, a quick, convenient approach in which cells are lysed in chaotropic salts and detergent and nucleic acids and covalently bound adducts then precipitated with alcohol. Here we show that RADAR fractionation followed by ELISA immunodetection can quantify adducts formed by wild-type and mutant Top1 derivatives encoded by two different bacterial pathogens, Y. pestis and M. tuberculosis, expressed in E. coli or M. smegmatis, respectively. For both enzymes, quantification of adducts by RADAR/ELISA produces results comparable to the more cumbersome classical approach of CsCl density gradient fractionation. The experiments reported here establish that RADAR/ELISA assay offers a simple way to ch...
Activation of efflux systems and the formation of biofilm are majorly adapted by microbes to resi... more Activation of efflux systems and the formation of biofilm are majorly adapted by microbes to resist antimicrobial agents. PPEF (bisbenzimidazole) targeting topoisomerase IA is observed to be an effective bactericidal agent against both Gram-positive and Gram-negative bacterial strains and thus can be developed as potent broad-spectrum antibiotic against MDR strains. PPEF treatment did not cause target specific mutation instead it leads to up-regulation of efflux gene in E. coli K12 as a mechanism of resistance. Microscopy, fluorescence spectroscopy and flow cytometry result demonstrate higher accumulation of PPEF in efflux gene deleted E. coli K12 mutants, and also suggest that Carbonyl Cyanide 3-Chlorophenylhydrazone (CCCP), resist the efflux of PPEF, and thus increases efficacy of PPEF. Herein, we report, PPEF and CCCP synergistically killed the persistent bacterial cells, which are not killed by PPEF alone. The above two compounds together inhibited biofilm formation, eradicate p...
In an attempt to find potential anticancer agents, a series of novel ethyl 4-(3-(aryl)-1-phenyl-1... more In an attempt to find potential anticancer agents, a series of novel ethyl 4-(3-(aryl)-1-phenyl-1H-pyrazol-4-yl)-2-oxo-6-(pyridin-3-yl)cyclohex-3-enecarboxylates 5a-i and 5-(3-(4-fluorophenyl)-1-phenyl-1H-pyrazol-4-yl)-3-(pyridin-3-yl)-4,5-dihydropyrazole-1-carbothioamides 6a-i were designed, synthesized and evaluated for their topoisomerase IIα inhibitory activity and in vitro cytotoxicity against a panel of cancerous cell lines (MCF-7, NCI-H460, HeLa) and a normal cell line (HEK-293T). Molecular docking studies of all the synthesized compounds into the binding site of topoisomerase IIα protein (PDB ID: 1ZXM) were performed to gain a comprehensive understanding into plausible binding modes. These compounds were also screened for in silico drug-likeliness properties on the basis of the absorption, distribution, metabolism and excretion (ADME) prediction. Among all the synthesized compounds, analogue 5d showed superior cytotoxicity with an IC50 value of 7.01±0.60μM for HeLa, 8.55±0.3...
Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the deve... more Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the development of new antibacterial agents that are impacted by target-mediated cross resistance with fluoroquinolones. The present study demonstrates the successful synthesis and evaluation of bisbenzimidazole analogues as Escherichia coli topoisomerase IA inhibitors. 5-(4-Propylpiperazin-1-yl)-2-[2'-(4-ethoxyphenyl)-5'-benzimidazolyl]benzimidazole (12b) showed significant relaxation inhibition activity against EcTopo 1A (IC50 = 2 ± 0.005 μM) and a tendency to chelate metal ion. Interestingly, these compounds did not show significant inhibition of E. coli DNA gyrase and hTop 1 even up to 100 μM. Compound 12b has shown lowest MIC against E. coli strains among 24 compounds evaluated. The binding affinity constant and binding free energy of 12b with EcTopo 1A was observed 6.8 × 10(6) M(-1) and -10.84 kcal mol(-1) from isothermal titration calorimetry (ITC), respectively. In vivo mouse sys...
Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the deve... more Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the development of new antibacterial agents that are impacted by target-mediated cross resistance with fluoroquinolones. The present study demonstrates the successful synthesis and evaluation of bisbenzimidazole analogues as Escherichia coli topoisomerase IA inhibitors. 5-(4-Propylpiperazin-1-yl)-2-[2'-(4-ethoxyphenyl)-5'-benzimidazolyl]benzimidazole (12b) showed significant relaxation inhibition activity against EcTopo 1A (IC50 = 2 ± 0.005 μM) and a tendency to chelate metal ion. Interestingly, these compounds did not show significant inhibition of E. coli DNA gyrase and hTop 1 even up to 100 μM. Compound 12b has shown lowest MIC against E. coli strains among 24 compounds evaluated. The binding affinity constant and binding free energy of 12b with EcTopo 1A was observed 6.8 × 10(6) M(-1) and -10.84 kcal mol(-1) from isothermal titration calorimetry (ITC), respectively. In vivo mouse systemic infection and neutropenic thigh model experimental results confirmed the therapeutic efficacy of 12b, suggesting further development of this class of compounds as antibacterial agents.
Topoisomerases are proven drug targets, but antibiotics that poison bacterial Topoisomerase 1 (To... more Topoisomerases are proven drug targets, but antibiotics that poison bacterial Topoisomerase 1 (Top1) have yet to be discovered. We have developed a rapid and direct assay for quantification of Top1-DNA adducts that is suitable for high throughput assays. Adducts are recovered by “RADAR fractionation”, a quick, convenient approach in which cells are lysed in chaotropic salts and detergent and nucleic acids and covalently bound adducts then precipitated with alcohol. Here we show that RADAR fractionation followed by ELISA immunodetection can quantify adducts formed by wild-type and mutant Top1 derivatives encoded by two different bacterial pathogens, Y. pestis and M. tuberculosis, expressed in E. coli or M. smegmatis, respectively. For both enzymes, quantification of adducts by RADAR/ELISA produces results comparable to the more cumbersome classical approach of CsCl density gradient fractionation. The experiments reported here establish that RADAR/ELISA assay offers a simple way to ch...
Activation of efflux systems and the formation of biofilm are majorly adapted by microbes to resi... more Activation of efflux systems and the formation of biofilm are majorly adapted by microbes to resist antimicrobial agents. PPEF (bisbenzimidazole) targeting topoisomerase IA is observed to be an effective bactericidal agent against both Gram-positive and Gram-negative bacterial strains and thus can be developed as potent broad-spectrum antibiotic against MDR strains. PPEF treatment did not cause target specific mutation instead it leads to up-regulation of efflux gene in E. coli K12 as a mechanism of resistance. Microscopy, fluorescence spectroscopy and flow cytometry result demonstrate higher accumulation of PPEF in efflux gene deleted E. coli K12 mutants, and also suggest that Carbonyl Cyanide 3-Chlorophenylhydrazone (CCCP), resist the efflux of PPEF, and thus increases efficacy of PPEF. Herein, we report, PPEF and CCCP synergistically killed the persistent bacterial cells, which are not killed by PPEF alone. The above two compounds together inhibited biofilm formation, eradicate p...
In an attempt to find potential anticancer agents, a series of novel ethyl 4-(3-(aryl)-1-phenyl-1... more In an attempt to find potential anticancer agents, a series of novel ethyl 4-(3-(aryl)-1-phenyl-1H-pyrazol-4-yl)-2-oxo-6-(pyridin-3-yl)cyclohex-3-enecarboxylates 5a-i and 5-(3-(4-fluorophenyl)-1-phenyl-1H-pyrazol-4-yl)-3-(pyridin-3-yl)-4,5-dihydropyrazole-1-carbothioamides 6a-i were designed, synthesized and evaluated for their topoisomerase IIα inhibitory activity and in vitro cytotoxicity against a panel of cancerous cell lines (MCF-7, NCI-H460, HeLa) and a normal cell line (HEK-293T). Molecular docking studies of all the synthesized compounds into the binding site of topoisomerase IIα protein (PDB ID: 1ZXM) were performed to gain a comprehensive understanding into plausible binding modes. These compounds were also screened for in silico drug-likeliness properties on the basis of the absorption, distribution, metabolism and excretion (ADME) prediction. Among all the synthesized compounds, analogue 5d showed superior cytotoxicity with an IC50 value of 7.01±0.60μM for HeLa, 8.55±0.3...
Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the deve... more Novel bisbenzimidazole inhibitors of bacterial type IA topoisomerase are of interest for the development of new antibacterial agents that are impacted by target-mediated cross resistance with fluoroquinolones. The present study demonstrates the successful synthesis and evaluation of bisbenzimidazole analogues as Escherichia coli topoisomerase IA inhibitors. 5-(4-Propylpiperazin-1-yl)-2-[2'-(4-ethoxyphenyl)-5'-benzimidazolyl]benzimidazole (12b) showed significant relaxation inhibition activity against EcTopo 1A (IC50 = 2 ± 0.005 μM) and a tendency to chelate metal ion. Interestingly, these compounds did not show significant inhibition of E. coli DNA gyrase and hTop 1 even up to 100 μM. Compound 12b has shown lowest MIC against E. coli strains among 24 compounds evaluated. The binding affinity constant and binding free energy of 12b with EcTopo 1A was observed 6.8 × 10(6) M(-1) and -10.84 kcal mol(-1) from isothermal titration calorimetry (ITC), respectively. In vivo mouse sys...
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