In vitro antimicrobial activity of a novel propolis formulation (Actichelated propolis)

Aims: This study compared in vitro activities of Actichelated® propolis (a multicomposite material obtained with mechano-chemichal activation) and of a hydroalcoholic extract of propolis. Methods and Results: Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), determined by means of microdilution broth method, against five strains of Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae, Enterococcus spp., Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa, showed a greater potency of Actichelated® propolis (MIC range: 0.016-4 mg flavonoids ml ^-1) in respect to the hydroalcoholic extract (MIC range: 0.08-21.4 mg flavonoids ml^-1). Concentrations of Actichelated® propolis active against adenovirus, influenza virus, parainfluenza virus and herpes virus type 1 were at least 10 times lower than those of the hydroalcoholic extract. Preincubation of Strep. pyogenes and H. influenzae with subinhibitory concentrations of Actichelated® propolis (1/4 and 1/8 x MIC) significantly reduced the number of bacteria that adhered to human buccal cells. Conclusions: Actichelated® propolis has proven to possess antibacterial and antiviral activity higher than a hydroalcoholic extract, being also able to interfere on bacterial adhesion to human oral cells. Significance and Impact of the Study: This new formulation of propolis showing better antimicrobial and physical characteristics could improve the application of propolis in respiratory tract infections.