Search for portuguese propolis antimicrobial activity in a wide range of microorganisms

Abstract

Propolis is a bee product composed by several compounds such as waxes, resins, essential oils and other organic compounds. Over the last decades, several studies have shown a wide range of biological and pharmacological properties for propolis from different provenance. Due to this large spectrum of bioactivities, such as antimicrobial, antioxidant, anti-inflammatory, and antitumor, among others, this product can become an alternative, economic and safe source of natural bioactive compounds. Propolis’ antimicrobial action has been widely reported, either in vivo or in vitro, using propolis extracts or its isolated compounds. However, Portuguese propolis has earned little attention and its antimicrobial potential remains to be studied and characterized. This study reports the in vitro screening for the antimicrobial potential of a Portuguese propolis ethanol extract against a panel of Gram-positive and Gram-negative bacteria, as well as a group of yeasts, using the broth microdilution assay. Propolis was collected in the Summer of 2010 and extracted three times with ethanol at room temperature. The obtained solutions were filtered and pooled giving a propolis ethanol extract (PEE). Microorganisms were incubated with PEE and cell viability was assessed with serial concentrations, after 24 or 48 hours. Results showed that Portuguese propolis exhibits an efficient antimicrobial action either against yeasts or bacteria. In general, Gram-positive bacteria are more sensitive than Gram-negative bacteria, as has been widely documented for propolis samples from different origins. The present work also allowed the selection of the most sensitive bacteria and yeasts to be used as indicator strains in further studies.