Design, synthesis and activity evaluation of usnic acid monoesterification derivatives.

A new series of usnic acid (UA) monoesterified derivatives were designed and synthesised using UA () as starting material. The structural characterisation of all compounds was elucidated using H-NMR and C-NMR spectral data. studies demonstrated thatmost UA derivatives exhibited higher inhibitory activity against and . Among them, compound displayed the highest inhibitory activity against with a minimum inhibitory concentration (MIC) of 32 μg/mL. Compounds , , , and demonstrated superior inhibition of (MIC, 16 μg/mL) and biofilm formation in a concentration-dependent manner. With the exception of , compounds , , and were all more effective than UA in inhibiting biofilms. This research highlights the potential of UA monoesterified derivatives for the development of dual antimicrobial and antibiofilm agents.