Effects of Cameroonian propolis and its cycloartane-type triterpene acids on bacterial quorum-sensing and biofilm formation

Propolis is popular for its health beneficial properties most especially, for its antimicrobial activity. 27-Hydroxymangiferonic acid (1), Ambolic acid (2) and Mangiferonic acid (3) were isolated from Anti-quorum sensing activity at MIC indicated that the most active sample was the extract with inhibition diameter zone of 18.0±1.0 mm, while compounds 1, 2 and 3 had inhibition zones of 12.0±0.5 mm, 9.0±1.0 mm and 12.3±1.0 mm respectively. The samples inhibited the P. aeruginosa PA01 swarming motility at the three tested concentrations (50, 75 and 100 μg/ml) in a dose-dependent manner. The propolis extract was able to inhibit biofilm formation by S. aureus, E. coli, P. aeruginosa, C. albicans and C. tropicalis at MIC concentration, compound 1 showed biofilm inhibition on S. aureus, L. monocytogenes, E. faecalis, E. coli and C. tropicalis at MIC and MIC/2, compound 2 inhibited the formation of biofilm at MIC on S. aureus, E. faecalis, E. coli, S. typhi, C. albicans and C. tropicalis, compound 3 inhibited biofilm formation on E. faecalis, E. coli, C. albicans and C. tropicalis and further biofilm inhibition on E. coli at MIC/4 and MIC/8. The results indicate that propolis and its compounds can reduce virulence factors of pathogenic bacteria.