Cationic 7-Alkoxy-3-Amino coumarin amphiphiles achieve potent antimicrobial activity within a cLogP range of 0.75-1.82

The escalating crisis of antimicrobial resistance (AMR) necessitates the development of novel antimicrobial agents with resistance-evading mechanisms. Cationic antimicrobial peptides (CAMPs) are naturally occurring molecules that demonstrate potent broad-spectrum activity with a lower propensity for resistance development. Synthetic mimetics of CAMPs offer a cost-effective pathway to new therapeutics. While our previous work identified amphiphilic coumarin derivatives active against MRSA and biofilms, the precise relationship between compound lipophilicity and antimicrobial activity for this class remained undefined, hindering rational design efforts.

Researchers designed and synthesized six cationic coumarin amphiphiles with systematically varied lipophilic character to define an optimal activity window. These compounds were characterized and evaluated against a panel of clinically relevant pathogenic bacteria (E. coli, K. pneumoniae, A. baumannii, P. aeruginosa, MRSA) and fungi (C. albicans, C. neoformans). The primary endpoint was the determination of minimum inhibitory concentration (MIC) values.

The study successfully established a critical lipophilicity window for potent antimicrobial activity of these cationic coumarin amphiphiles. When existing in their cationic state, a cLogP range of 0.75-1.82 correlated with the best activity across the tested pathogens. Compounds within this optimal range demonstrated remarkable potency. > Minimum inhibitory concentration (MIC) values were as low as 0.02 µg/mL against Cryptococcus neoformans and 1 µg/mL against MRSA for derivatives falling within the identified lipophilicity window. This precise definition of the lipophilicity-activity relationship provides crucial guidance for future rational design.