An Evaluation of Single Electron Transfer Reduction Products of 3-Oxoindoles as Antibacterial Agents

Background: Antimicrobial resistance is growing quickly throughout the world due to extensive and indiscriminate use of antibiotics. Reduction of indole derivatives comprises a very important and interesting branch of synthetic organic chemistry as these reactions are utilized in the synthesis of several drugs, dyes, agrochemicals and higher alkaloids.

Objective: The objective of the present study is to assess the antibacterial properties of six indole derivatives viz, 3-(Naphth-1-y - methyl) –indole (II), 3-(1-Naphthylcarbonyl – indole (III), 3,3' –diformyl-2,2' –bis indole (IV), 1,4- (3,3' –di indolyl) – 1,4-dioxobutane (V), 3-benzoyl indole (VI) and 1,1 – bis – (3-indolyl)- ethane (VII) synthesized by single electron transfer reduction of 3-formylindole (I) against two Gram +ve and two Gram –ve bacteria which usually cause human infections.

Methods: Synthesis of 3-formyl indole from which the indole derivatives were prepared were further characterized by IR and NMR analysis. The six synthesized compounds were screened for their antibacterial activity by agar diffusion method and the activities were further confirmed by determining their MIC values by microdilution technique.

Results: All of the compounds more or less showed activity against different bacterial species except compound IV which showed activity only against B. subtilis. Compound II exhibited the most potent activity with lower MIC values against two Gram –ve and one Gram +ve bacteria of which the Gram –ve ones are known to be responsible for nosocomial and community acquired infections.

Conclusion: Compound II being the most potent active compound may serve as leads for further optimization most likely to contribute as a broad spectrum antibiotic.