Design, synthesis and molecular modeling of isatin-aminobenzoic acid hybrids as antibacterial and antibiofilm agents.

Number of factors, including newly emerging infectious diseases and an increase in multi-drug resistant microbial pathogens with particular relevance for Gram-positive bacteria, make the treatment of infectious diseases in hospital-based healthcare a major challenge in the medical community. 4-Aminobenzoic acid (PABA), has demonstrated a variety of biological actions particularly, antimicrobial activity. In our study we coupled this vitamin-like molecule with different isatin derivatives. We investigated the antibacterial activity of the synthesized Schiff's bases. The compounds showed high selective activity against Gram-positive bacteria and showed weak or no activity against both Gram-negative bacteria and fungi. Compound 2a showed highest activity against S. aureus and B. subtilis (MIC 0.09 mmol/L). Additionally, these substances exhibit strong anti-B. Subtilis biofilm formation. We were able to shed insight on the binding mode of these new inhibitors using in silico docking of the compounds in the binding sites of a 3D structure of B. subtilis histidine kinase/Walk. The binding free energy of the compound 2a to the catalytic domain walk, of histidine kinase enzyme of B. subtilis bacteria, was calculated using molecular mechanics/generalized born surface area scoring. The key residues for macromolecule-ligand binding were postulated. The optimized 3D protein-ligand binding modes shed light on the B. subtilis HK/Walk-ligand interactions that afford a means to assess binding affinity to design new HK/Walk inhibitor as antibacterial agents.

Design, synthesis and molecular modeling study of substituted indoline-2-ones and spiro[indole-heterocycles] with potential activity against Gram-positive bacteria.

Longstanding and firsthand infectious diseases are challenging community health threats. A new series of isatin derivatives bearing ß-hydroxy ketone, chalcone, or spiro-heterocycle moiety, was synthesized in a good yield. Chemical structures of the synthesized compounds were elucidated using spectroscopic techniques and elemental analysis. Antibacterial activities of the compounds were then evaluated in vitro and by in silico modeling. The compounds were more active against Gram-positive bacteria, Staphylococcus aureus (MIC = 0.026-0.226 mmol L-1) and Bacillus subtilis (MIC = 0.348-1.723 mmol L-1) than against Gram-negative bacteria (MIC = 0.817-7.393 mmol L-1). Only 3-hydroxy-3-(2-(2,5-dimethylthiophen-3-yl)-2-oxoethyl)indolin-2-one (1b) was found as active as imipenem against S. aureus (MIC = 0.026 mmol L-1). In silico docking of the compounds in the binding sites of a homology modeled structure of S. aureus histidine kinase-Walk allowed us to shed light on the binding mode of these novel inhibitors. The highest antibacterial activity of 1b is consistent with its highest docking score values against S. aureus histidine kinase.

1, 3, 4-Thiadiazole and 1, 2, 4-triazole-3(4 H )-thione bearing salicylate moiety: synthesis and evaluation as anti- Candida albicans

Abstract Dramatically increased occurrence of both superficial and invasive fungal infections has been observed. Candida albicans appear to be the main etiological agent of invasive fungal infections. The anti-C. albicans activity of thiosemicarbazide, 1,3,4-Thiadiazole, and 1,2,4-triazole-3(4H)-thione compounds (compounds 3-23) were investigated. The MIC values of thiadiazole and triazole derivatives 10-23 were in the range of 0.08-0.17 µmol mL-1, while that of fluconazole was 0.052 µmol mL-1. Compound 11 (5-(2-(4-chlorobenzyloxy)phenyl)-N-allyl-1,3,4-thiadiazol-2-amine) and compound 18 (5-(2-(4-chlorobenzyloxy)phenyl)-4-allyl-2H-1,2,4-triazole-3(4H)-thione) were found to be the most active compounds, with MIC values of 0.08 µmol mL-1. The newly synthesized thiadiazole and triazole compounds (compounds 10-23) showed promising anti-Candida activity. The allyl substituent-bearing compounds 11 and 18 exhibited significant anti-Candida albicans activity and showed a binding mode as well as the fluconazole x-ray structure.