Synthesis, docking, ADMET prediction, cytotoxicity and antimicrobial activity of oxathiadiazole derivatives

Design, Synthesis, DFT, docking Studies, and antimicrobial evaluation of novel benzimidazole containing sulphonamide derivatives

In silico approaches have been employed to design a new series of benzimidazole-containing sulphonamide derivatives and qualified compounds have been synthesized to analyze their potential as antimicrobial agents. Antibacterial screening of all synthesized compounds was done using the broth microdilution method against several human pathogenic bacteria, viz. Gram-positive bacteria [B. cerus (NCIN-2156), B. subtilis (ATCC-6051), S. aureus (NCIM-2079)] and Gram-negative bacteria [P. aeruginosa (NCIM-2036), E. coli (NCIM-2065), and a drug-resistant strain of E. coli (U-621)], and the compounds presented admirable MIC values, ranging between 100-1.56 µg/mL. The combinatorial analysis showed the magnificent inhibitory efficiency of the tested compounds, acquired equipotent to ten-fold more potency compared to original MIC values. An immense synergistic effect was exhibited by the compounds during combination studies with reference drugs chloramphenicol and sulfamethoxazole was presented as fractional inhibitory concentration (∑FIC). Enzyme inhibition studies of all synthesized compounds were done by using peptidyl transferase and dihydropteroate synthase enzymes isolated from E. coli and S. aureus and each of the compound presented the admirable IC50 values, where the lead compound 3 bound to peptidyl transferase (of S. aureus with IC50 363.51 ± 2.54 µM and E. coli IC50 1.04 ± 0.08 µM) & dihydropteroate synthase (of S. aureus IC50 3.51 ± 0.82 µM and E. coli IC50 2.77 ± 0.65 µM), might account for the antimicrobial effect, exhibited excellent inhibition potential. Antifungal screening was also performed employing food poisoning methods against several pathogenic fungal species, viz A. flavus, F. oxysporum, A. niger, and A. brassicae. The obtained result indicated that few compounds can prove to be a potent drug regimen against dreaded MDR strains of microbes. Structural activity relationship (SAR) analysis and docking studies reveal that the presence of electron-withdrawing, polar, and more lipophilic substituents positively favor the antibacterial activity, whereas, electron-withdrawing, more polar, and hydrophilic substituents favor the antifungal activities. A robust coherence has been found in in-silico and in-vitro biological screening results of the compounds.

Design, synthesis and antimicrobial activity of novel quinoline derivatives: an in silico and in vitro study

A series of new quinoline derivatives has been designed, synthesized and evaluated as antibacterial and antifungal agents functioning as peptide deformylase enzyme (PDF) inhibitors and fungal cell wall disruptors on the basis of computational and experimental methods. The molecular docking and ADMET assessment aided in the synthesis of quinoline derivatives starting from 6-amino-4-methyl-1H-quinoline-2-one substituted with different types of sulfonyl/benzoyl/propargyl moieties. These newly synthesized compounds were evaluated for their in vitro antibacterial and antifungal activity. Antibacterial screening of all compounds showed excellent MIC value (MIC, 50 - 3.12 µg/mL) against bacterial strains, viz. Bacillus cerus, Staphylococcus, Pseudomonas and Escherichia coli. Compounds 2 and 6 showed better activity. Fractional inhibitory concentration (FIC) values of compounds were lowered by 1/2 to 1/128 of the original MIC values when a combinatorial screening with reference drugs was performed. Further, antifungal screening against fungal strains, viz. A. flavus, A. niger, F. oxysporum and C. albicans also showed that all compounds were potentially active and compound 6 being the most potent. Further, the cytotoxicity experiments revealed that compound 6 was the least toxic molecule. The molecular dynamics (MD) simulation investigations elucidated the conformational stability of compound 6-PDF complex with flexible binding pocket residues. The highest number of stable hydrogen bonds with the PDF residues during the entire simulation time illustrated strong binding affinity of compound 6 with PDF.Communicated by Ramaswamy H. Sarma.

Attenuation of Las/Rhl quorum sensing regulated virulence and biofilm formation in Pseudomonas aeruginosa PAO1 by Artocarpesin

The emergence of multidrug resistance and increased pathogenicity in microorganisms is conferred by the presence of highly synchronized cell density dependent signalling pathway known as quorum sensing (QS). The QS hierarchy is accountable for the secretion of virulence phenotypes, biofilm formation and drug resistance. Hence, targeting the QS phenomenon could be a promising strategy to counteract the bacterial virulence and drug resistance. In the present study, artocarpesin (ACN), a 6-prenylated flavone was investigated for its capability to quench the synthesis of QS regulated virulence factors. From the results, ACN showed significant inhibition of secreted virulence phenotypes such as pyocyanin (80%), rhamnolipid (79%), protease (69%), elastase (84%), alginate (88%) and biofilm formation (88%) in opportunistic pathogen, Pseudomonas aeruginosa PAO1. Further, microscopic observation of biofilm confirmed a significant reduction in biofilm matrix when P. aeruginosa PAO1 was supplemented with ACN at its sub-MIC concentration. Quantitative gene expression studies showed the promising aspects of ACN in down regulation of several QS regulatory genes associated with production of virulence phenotypes. Upon treatment with sub-MIC of ACN, the bacterial colonization in the gut of Caenorhabditis elegans was potentially reduced and the survival rate was greatly improved. The promising QS inhibition activities were further validated through in silico studies, which put an insight into the mechanism of QS inhibition. Thus, ACN could be considered as possible drug candidate targeting chronic microbial infections.

Current Status and Structure Activity Relationship of Privileged Azoles as Antifungal Agents (2016-2020)

Fungal infections have major contribution to the infectious related deaths in recent century. The issue has gotten worse with the advent of immunity impairing conditions such as HIV epidemic. Eukaryote nature of fungal pathogens leads to harder eradication than bacterial infections. Given the importance of the problem, considerable efforts have been put on the synthesis and biological assessment of azole-based chemical scaffolds and their bioisosteres. The emergence of validated macromolecular targets within different fungal species inspires structure-based drug design strategies toward diverse azole-based agents. Despite of advantageous features, emergence of drug-resistant fungal species restrict the applicability of current azoles as the first-line antifungal agents. Consequently, it appears advisable to elucidate SARs and chemical biodiversity within antifungal azoles. Current contribution was devoted to a brief look at clinically applied drugs, structure-based classification of azole antifungals and their structure activity relationships (SARs). Reviewed molecules belong to the antifungal structures that were reported throughout 2016-2020.

Molecular modelling, synthesis and antimicrobial evaluation of benzimidazole nucleoside mimetics

A series of new N-1-(β-d-ribofuranosyl) benzimidazole derivatives has been designed using in silico methods and synthesized as probable antimicrobial agents. Further, the compounds were assessed for their antibacterial and antifungal activity. Antibacterial screening was done by employing broth micro-dilution method and compounds exhibited excellent inhibitory activity (MIC, 50-1.56 µg/mL) against different human pathogenic bacteria, viz. B. cerus, B. subtilis, S. aureus, E. coli and P. aeruginosa and drug resistant strain (DRS) of E. coli. A great synergistic effect was observed during evaluation of ∑FIC, where a combination study was performed using standard references, viz. chloramphenicol and kanamycin. The MIC data obtained from different methods of combination approach revealed 4-128 fold more potency compared to compounds tested alone. The results clearly indicated the possibility of these compounds as active ingredients of drug regimen used against MDR strains. Antifungal screening were also performed employing two different methods, viz. serial dilution method and zone inhibition method, clearly indicated that compounds were also potentially active against several species of pathogenic fungal strains, viz. A. flavus, A. niger, F. oxysporum and C. albicans. The assessment of structure activity relationship (SAR) clearly revealed that presence of less polar and more hydrophobic substituents positively favours the antibacterial activity, conversely, more polar and hydrophilic substituents favours the antifungal activities. Thus, the results positively endorsed the compounds as potent antibacterial and antifungal agents which could be developed as possible drug regimens.

Toxic Prediction of Pyrrolizidine Alkaloids and Structure-Dependent Induction of Apoptosis in HepaRG Cells

Pyrrolizidine alkaloids (PAs) are common phytotoxins and could cause liver genotoxicity/carcinogenicity following metabolic activation. However, the toxicity of different structures remains unclear due to the wide variety of PAs. In this study, the absorption, distribution, metabolism, excretion, and toxicity (ADMET) of 40 PAs were analyzed, and their toxicity was predicted by Komputer Assisted Technology (TOPKAT) using Discovery Studio software. The in silico results showed that all PAs except retronecine had good intestinal absorption, and all PAs were predicted to have different toxicity ranges. To verify the predictive results, 4 PAs were selected to investigate cell injury and possible mechanisms of the differentiation in HepaRG cells, including retronecine type of twelve-membered cyclic diester (retrorsine), eleven-membered cyclic diester (monocrotaline), noncyclic diester (retronecine), and platynecine type (platyphylline). After 24 h exposure, retronecine-type PAs exhibited concentration-dependent cytotoxicity. The high-content screening assay showed that cell oxidative stress, mitochondrial damage, endoplasmic reticulum stress, and the concentration of calcium ions increased, and neutral lipid metabolism was changed notably in HepaRG cells. Induced apoptosis by PAs was indicated by cell cycle arrest in the G2/M phase, disrupting the mitochondrial membrane potential. Overall, our study revealed structure-dependent cytotoxicity and apoptosis after PA exposure, suggesting that the prediction results of in silico have certain reference values for compound toxicity. A 1,2-membered cyclic diester seems to be a more potent apoptosis inducer than other PAs.