Ethanolic extract of Turkish bee pollen and propolis: phenolic composition, antiradical, antiproliferative and antibacterial activities

Abstract

Bee pollen and propolis are considered as health-promoting foods with many therapeutic (antibacterial, antifungal and antioxidant) activities. This study analyzed the phenolic profile and the antioxidant properties of Turkish bee pollen and propolis ethanolic extracts and assayed their antiproliferative effect on myeloma cells and in vitro antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity assays included agar well diffusion and microdilution methods. The phenolic profile and several aromatic compounds of the extracts were determined by high-performance liquid chromatography with diode-array detection (HPLC-DAD). The antiproliferative activity on myeloma cells was determined by MTT test. The propolis extract had higher total phenolic content (TPC), free-radical scavenging activity (DPPH) and half-maximal inhibitory concentration (IC₅₀) than the pollen ethanolic extract. Benzoic and cinnamic acid were the most abundant aromatic substances in the pollen and propolis extracts, respectively. The IC₅₀ values of pollen and propolis extracts on myeloma cells were 1.49% and 2.88%, respectively. The propolis extract was active against S. aureus and E. coli, but not P. aeruginosa. The pollen extract presented no detectable inhibition zone against the three bacterial strains. The minimum inhibitory concentration (MIC) of both extracts for S. aureus and E. coli was 0.63% (w/v). The minimum bactericidal concentration (MBC) of the propolis extract was 1.25% for S. aureus and E. coli. MIC could not be determined for the pollen extract in the tested bacteria. The pollen and propolis extracts did not exert antimicrobial activity against P. aeruginosa up to 2.5% concentration.