Comparison of Propolis Antimicrobial Activity Using Three Delivery Methods
M. DAETWYLER*, Y. EHRLICH, R. GREGORY (Indiana University School of Dentistry).
Propolis is a non-toxic product of honeybees, which contains flavonoids, phenols and aromatic
compounds. Ecuadorian Rainforest, LLC (EP) is propolis product that has been shown to be
beneficial in the treatment of a longstanding endodontic infection. In vitro studies at IUSD have
shown that EP has antibacterial properties against Fusobacterium nucleatum prominent in
primary endodontic infections. Different solvents are used to dissolve propolis and the propolis
extracts can be used as intracanal medicaments. The purpose of this in vitro study is to compare
the antimicrobial efficacy of EP extracts from three different solvents. Enterococcus faecalis and
Candida albicans were chosen as the test organisms. E. faecalis is mostly found in secondary
endodontic infections and C. albicans plays a pivotal role in biofilm formation. The solvents
used were dimethyl sulfoxide (DMSO), propylene glycol, and ethanol. EP was dissolved in each
solvent, the solution was centrifuged, and the supernatant was taken to test for antimicrobial
activities. E. faecalis and C. albicans were then grown in broth media with increasing
concentrations of the propolis extract. After incubating for 48 hours in 96 well plates, total
growth was measured using a SpectraMax 190 spectrophotometer. 120 µl aliquots were
separated to measure planktonic growth. Finally, by fixing the biofilm to the wells and staining
with crystal violet the biofilm formation could be measured. The results show clear inhibition of
total growth in all three propolis containing solvents in a dose-dependent manner. However,
further testing revealed strong antimicrobial activity in the higher concentrations of solvent
alone. This perhaps masks the effect of propolis and does not enable us to evaluate the effect of
the propolis independent of the solvent used. Further research would need to allow high
concentrations of propolis without the high concentration of solvent.