Synthesis of new coumarin derivatives and assessment of their antimicrobial efficacy.

AIM: Developing new antimicrobial agents in response to the urgent challenge of antimicrobial resistance.

METHODS

Synthesis of the targeted coumarins, elucidation of their structures using spectroscopic tools, and investigation of their antimicrobial activity.

RESULTS

Coumarin-pyrazole 11 with CF3 in the 3-position of the pyrazole ring displayed the lowest minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) with values of 1.95 and 15.6 µg/ml, respectively, against Bacillus pumilis. In addition, it exhibited the best inhibitory activity against Saccharomyces cerevisiae (MIC = 3.91 µg/ml) compared to the rest of the derivatives (7.81-62.5 µg/ml). Surprisingly, coumarin 14 with the S-CH3 group had higher ability to inhibit the Staphylococcus faecalis strain with an MIC value of 1.95 µg/ml, which is twice that of penicillin G (MIC = 3.91 µg/ml). At the same time, compounds 6, 8, 11, 16, and penicillin G showed similar activity with an MIC value of 3.91 µg/ml against Staphylococcus faecalis. Also, the lowest MIC value (3.91 µg/ml) was obtained for S-CH3 derivative 14 against Enterobacter cloacae. Coumarins 14 and 1,3,4-thiadiazine derivative 6 recorded the lowest MBC (15.6 µg/ml) against Escherichia coli.

CONCLUSION

Finally, it can be concluded that some designed coumarins have a high potential to act as potent antimicrobial agents. Some of them displayed higher efficacy than or equal to the reference drug.