Synthesis and evaluation of antibacterial and anti-inflammatory properties of naturally occurring coumarins

Coumarins are a group of heterocyclic compounds naturally present in a large variety of plant families. Nevertheless, oxyprenylated coumarins have been only recently seen as valuable and promising biologically active phytochemicals. In this study, we synthesized three naturally occurring O-prenylcoumarins (1), (2), and (3), and evaluated their antibacterial and anti-inflammatory properties in view of their therapeutic potential against periodontal disease. The three O-prenylcoumarins were synthesized using well-known schemes leading to the chromen-2-one nucleus. The periodontal pathogen Porphyromonas gingivalis was found to be highly susceptible to all three O-prenylcoumarins with minimal inhibitory concentration values in the range of 12.5–25 mg/ml; the non-prenylated forms of the coumarins did not show any activity. The antibacterial activity of (1), (2), and (3) appeared to result from its ability to permeate the cell membrane. Using the U937-3xkB-LUC human monocytic cell line, compounds (2) and (3) dose-dependently inhibited lipopolysaccharide-induced NF-kB activation, while (1) did not. The non-prenylated forms of the coumarins were either inactive or much less potent. In conclusion, O-prenylcoumarins (2) and (3) by exhibiting a dual mode of action including antibacterial and anti-inflammatory activities may represent promising targeted therapeutic agents for localized treatment of periodontal diseases.