Inhibitory Activity of Brown Propolis Extracts on a Norfloxacin-Resistant Strain of Staphylococcus aureus

Brown propolis from northern Ceara, Brazil, was found to contain predominantly sesquiterpenes in its volatile profile. The ethanolic propolis extract yielded a substantial apolar fraction (80.07 +/- 1.47%) after liquid-liquid partitioning, which explains the low phenolic content (41.33 +/- 1.68 mg(GAE) g(EXT)(-1)). Phenolics, such as p-coumaric (0.13 +/- 0.04 mg g(EPE)(-1)), ferulic (1.07 +/- 0.09 mg g(EPE)(-1)), and trans-cinnamic (0.41 +/- 0.02 mg g(EPE)(-1)) acids, were detected in the EtOH-soluble extract. The apolar fraction was rich in triterpenes such as cycloartenol (12.85 +/- 2.80%), alpha-amyrenyl acetate (4.37 +/- 0.69%), and alpha-amyrin (3.89 +/- 0.62%). Despite the lack of a direct antibacterial activity against Staphylococcus aureus 1199-B, both fractions exhibited potentiating effects in combination with norfloxacin; these effects could be attributed to efflux pump inhibition. The apolar fraction was more effective than the EtOH-soluble one at reducing the minimum inhibitory concentration, producing similar results to chlorpromazine and ethidium bromide. The EtOH-soluble fraction exhibited cytostatic properties at lower concentrations, while the apolar fraction demonstrated better selectivity for PC3 and HL60 tumor cells. The findings highlight the biological potential of Brazilian brown propolis for application as a complementary agent in the treatment of S. aureus infections and as an alternative therapy for cancer treatment.

Automated summary

Brown propolis from Brazil contains mainly sesquiterpenes and an apolar fraction, with potential biological activities in combating Staphylococcus aureus infections and as an alternative treatment for cancer.