Chemical characterization and antibacterial action of brown propolis extract from Southern Brazil

Abstract

The aim of this study was to characterize chemically a sample of brown propolis and determine the time of action needed for eliminating microorganisms causing bovine mastitis. It was prepared hydroalcoholic extract of brown propolis (25 mg/mL) and this was evaluated for content of total phenolic compounds, total flavonoids, qualitative and quantitative analysis of phenolic compounds by liquid chromatography coupled to mass spectrometry and antibacterial activity against Escherichia coli, Staphylococcus spp, Streptococcus spp. It was found 34.39% and 13.46% of flavonoids and phenolic compounds, respectively, among which stand out ferulic acid (0.09 mg/g), caffeic acid (0.17 mg/g) and p-coumaric acid (3.39 mg/g). In the first 15 minutes incubation, all counts differed from the initial counts (p<0.01). With 15 minutes of exposure to the extract, Escherichia coli was inhibited by 38.72% and differed from the other bacterial genus (p<0.01, n=6). Staphylococcus spp. has had inhibition of 46.03% and Streptotococcus spp. of 50.8%. After 2 hours incubation, the genus Streptococcus was totally eliminated, Staphylococcus spp. after 3 hours and E. coli after 4 hours. Clearly, E. coli was more resistant bacteria than S. aureus. The other species of Staphylococcus and Streptococcus did not show large differences between the counts. We concluded that the composition of the brown propolis sample from Southern Brazil showed large levels of phenolic acids with proven antibacterial action, what explains the bactericidal activity found.