Green synthesis, antibacterial evaluation and QSAR analysis of some isatin Schiff bases

Twelve isatin Schiff bases (1a-7a, 1b-5b) were prepared by reacting isatin and 5-bromoisatin with different anilines using green chemistry (microwave (MW) and ultrasound (US) assisted synthesis). The antibacterial activity of each compound was evaluated against nine standard and clinical bacterial strains using the Agar-well diffusion method. The lowest-obtained Minimum Inhibitory Concentration (MIC) was 78 mu g/mL against Pseudomonas aeruginosa for 1a and 1b. All the synthesized compounds were identified using IR, H-1 NMR, C-13 NMR and microanalysis. Quantitative Structure Activity Relationship (QSAR) and Molecular Electrostatic Potential Surface (MEPS) analyses were carried out to rationalize antibacterial activity of the synthesized compounds. Based on the QSAR analysis, including DFT-based, steric and hydrophobic descriptors, it was found that molecules with more hydrophobic character associated with less dipole moment act as antibacterial agents against Klebsiella pneumoniae ATCC700603. (C) 2020 Elsevier B.V. All rights reserved.