Design, synthesis and antimicrobial activity of novel benzothiazole analogs

In an attempt to design and synthesize a new class of antimicrobials, dialkyne substituted 2-aminobenzothiazole was reacted with various substituted aryl azides to generate a small library of 20 compounds (3a–t) by click chemistry. Structures of the newly synthesized compounds were established on the basis of spectral data. These compounds were screened for their antibacterial activity against Gram+ bacteria (Staphylococcus aureus and Enterococcus faecalis), Gram− bacteria (Salmonella typhi, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Shigella boydii) and antifungal activity against Candida tropicalis, Candida albicans, Candida krusei, Cryptococcus neoformans) as well as molds (Aspergillus niger, Aspergillus fumigatus). The compound 3e showed maximum potency against all Gram+/gram− bacterial strains with MIC value 3.12 μg/ml, which is two fold more active as compared to standard drug ciprofloxacin (MIC 6.25 μg/ml). However, all compounds were found ineffective against S. boydii (clinical isolate). Further, only one compound 3n was found to be the most active against all fungal strains with MIC value in the range of 1.56 μg/ml–12.5 μg/ml while the remaining compounds showed moderate to weak antifungal activity.

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► Novel benzothiazole analogs with different functionalities were synthesized by click chemistry.
► Screened against seven bacterial strains (gram+/gram−) & seven antifungal strains.
► Compound 3e showed MIC 3.12 μg/ml against bacterial strains. Ciprofloxacin showed MIC 6.25 μg/ml.
► Compound 3n was active against fungal strains with MIC value in the range 1.56 μg/ml–12.5 μg/ml.
► Good candidates for in vivo activities.