[Propolis' antimicrobial activity: what's new?]

Propolis is a hive product that bees manufacture from balsamic resins actively secreted by plants on leaf buds and barks. Propolis composition is highly variable, depending on the plant species and on the season of collection. However, propolis essentially contains resins, balsams, essential oils, flavonoids, vitamins, minerals and pollen, albeit at different concentrations. Although more than 300 constituents have been identified in propolis samples, biological activity is mainly due to few substances, such as flavonoids, terpens, caffeic, ferulic and cumaric acids and esters. Propolis is characterized by multifactorial activities, but only some of them have been substantiated by clinical and experimental evidence. It is widely acknowledged to exert antimicrobial activity against a wide range of microorganisms (bacteria, fungi and viruses), but also exerts antiinflammatory, anaesthetic, healing, vasoprotective, antioxidant, antitumoral, antiulcer and hepatoprotective activities. The wide spectrum of activities has led in recent years to the development of new technologies to improve propolis properties of the traditional hydroalcoholic extract. This paper reviews the antimicrobial properties of propolis, focusing on respiratory pathogens. These characteristics make propolis a valid option for therapy of upper respiratory tract infections.