The antimicrobial activities of 43 naturally occurring and synthetic coumarins were studied. Using a microtitre assay developed in-house, a range of Gram-positive and Gram-negative bacteria, including a hospital isolate of methicillin-resistant Staphylococcus aureus (MRSA), were utilised. The coumarins exhibiting good bioactivity (i.e. a lowminimum inhibitory concentration) against two S. aureus strains were then assessed for their antimicrobial activities against a range of eight clinically isolated MRSA strains. The study showed that nearly one-half of the tested compounds displayed antimicrobial activity. Sixteen of these coumarins also possessed resistance-modifying activity, which reversed the resistance mechanism in MRSA allowing the antimicrobial oxacillin to exert an enhanced effect against an MRSA hospital strain. When tested in combination with oxacillin, 8-iodo-5,7-dihydroxycoumarin (32) had a similar activity to vancomycin, which is the current drug of choice for the treatment of MRSA infections. (C) 2008 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Smyth, T., Ramachandran, V. N., & Smyth, W. F. (2009). A study of the antimicrobial activity of selected naturally occurring and synthetic coumarins. International Journal of Antimicrobial Agents, 33(5), 421-426. https://doi.org/10.1016/j.ijantimicag.2008.10.022