Synthesis and Anti-Staphylococcal Activity of 2,4-Disubstituted Diphenylamines

Infections caused by Staphylococcus aureus are ubiquitous and life threatening. Evolution of resistant strains has necessitated the need to continuously discover new drugs to combat such organisms. Diphenyl ethers, such as triclosan, have recently shown potential as antibacterial agents. In this study, a series of diphenyl amines were synthesized and evaluated for in vitro antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Pseudomonas putida) bacteria. Preliminary results showed that six of the twelve synthesized molecules were active against Staphylococcus aureus. Most notable amongst them were compounds 2(2,4-dinitrophenylamino) phenol and 2(2-dinitrophenylamino) phenol having minimum inhibitory concentration (MIC) in the range of 7.8-15.6 mu g mL(-1) and 7.8-62.5 mu g mL(-1) respectively for all the eight selected organisms. Five active compounds from the preliminary results were further screened against resistant S. aureus cultures where compounds 2(2,4-dinitrophenylamino) phenol, 2(2-dinitrophenylamino) phenol and 2-chloro-N-(2-(2,4-dichlorophenylamino) phenyl) acetamide gave encouraging results having MIC in the range 3.9-7.8 mu g mL(-1) for most of the organisms. Results obtained above for the selected organisms and the resistant S. aureus strains conclude that hydroxyl group at 2-position of ring B potentiates the antibacterial activity and overcomes the antibiotic resistance.