Phenolic Content and Antibiofilm Activity of Propolis Against Clinical MSSA Strains

Antibiofilm properties and the phenolic composition of propolis, collected from Bartın province of Turkey in the years of 2013 and 2012, were determined. Hexane, ethyl acetate and ethanol extracts of propolis were prepared and assessed for their antibiofilm activity (inhibition of biofilm formation and reduction of established biofilm) against the clinical methicillin sensitive Staphylococcus aureus (MSSA) strains and Staphylococcus aureus ATCC 33862. Ethyl acetate and ethanol extracts of propolis presented a greater effectiveness on biofilm inhibition of the tested bacteria compared to hexane extracts. The activity patterns showed slight variations in the two years. While 0.5 mg/mL ethyl acetate, ethanol and hexane extract solutions of the product in 2013 inhibited 92.89, 82.98 and 47.42% of biofilm formation of MSSA M20 strain, the inhibition percentage of the products of 2012 were determined to be 87.14%, 75.94% and 44.89% against the same bacterium (MSSA M20), respectively. The results of the validated liquid chromatography-electrospray tandem mass spectrometry (UPLC-ESI-MS/MS) analyses showed a strong relation between the activity and the phenolic composition of the extracts. Phenolic contents of the ethyl acetate and ethanol extracts were relatively higher than hexane extracts. Caffeic acid composition of ethyl acetate, ethanol and hexane extracts of the product in 2013 was detected as 23521.0, 16881.0 and 3522.8 µg/g, respectively. On the other hand, the caffeic acid contents of the product of 2012 was found to be lower than those of 2013 (19100.0, 10416.0 and 2322.5 µg/g for ethyl acetate, ethanol and hexane extracts, respectively). Consequently, the findings have shown that propolis extracts possessed good antibiofilm activity against clinical staphylococci, and its phenolic composition has been affected by the year of collection.