A Comparison of the Bioactivity of Usnic Acid versus Methylphloroacetophenone

The identification of natural products that disrupt biofilm formation has become an area of recently expanded interest in combating antibiotic resistance. The formation of biofilms has been correlated with increased pathogenesis in many strains of Gram-negative bacteria. Molecules that disrupt the formation of biofilms therefore represent a potentially novel way to combat pathogenesis. Lichen natural products are an underexplored source of biofilm disrupting natural products. We have investigated the biofilm disrupting activity of the lichen natural product usnic acid (UA) in comparison to the biosynthetic precursor methylphloroacetophenone (MPA). We have observed in our assays that UA is more bioactive than MPA, suggesting a rationale for the biosynthesis of UA in a wide variety of lichen species. These results suggest that lichen natural products may prove to be a rich source of biofilm inhibitors.