Comparative study of antibiofilm, cytotoxic activity and chemical composition of Algerian propolis

Antimicrobial agents are one of the strategies for inhibition of biofilm formation. But, most antimicrobials are not often effective in controlling of biofilm formation. Therefore, finding of new materials that have biofilm inhibitory effects is so important. In this regard, we aimed to determine the antibiofilm and cytotoxic effect of five Algerian propolis extracts obtained by extraction in solvents of varying polarity. Propolis extracts were tested for their ability to inhibit biofilm formation and to reduce preformed biofilm of eight bacterial strains including reference strains of Staphylococcus aureus (S. aureus ATCC29213 and S. aureus ATCC33862), three methicillin-resistant S. aureus (M10-1, M18-3, and M20-1), Enterococcus faecalis ATCC19433, Micrococcus luteus NRRL-B1013, and Yersinia enterocolitica RSKK1501. Cytotoxic activities of propolis extracts were determined using MTT test. Chemical investigation was performed using ultra-performance liquid chromatography with electrospray ionization coupled to tandem mass spectrometry (UPLC-ESI-MS/MS). All tested extracts exhibited the highest eradicating capability for S. aureus reference strains and methicillin-resistant strains, especially MRSA18-3 and MRSA20-1.The reduction of biofilm formation was found to be significantly affected by the used solvent for maceration, the tested bacterial strains, and the origin of tested propolis. In addition, biofilm reduction of Algerian propolis seemed to be dose-dependent. Moreover, all extracts showed high cytotoxic activity in colon adenocarcinoma cells. In addition, twenty-six phenolic compounds were detected. Difference between the amounts of detected compounds was found to be significant. Caffeic and ferulic acids were the main compounds in the tested extracts. These results suggest that those compounds might be responsible for the observed antibiofilm and cytotoxic activities of propolis extracts.