Molecular Mechanism Underlying the Therapeutic Activities of Propolis: A Critical Review

Propolis, a resinous bee-hive product referred as “bee glue”, is collected from various plant sources, such as buds of conifer and poplar trees, by honeybees (Apis mellifera). Honeybees blend this resinous non-toxic substance with their salivary secretions and wax flakes secreted from special glands on their abdomens. Propolis has been used as a healing agent for thousands of years in folk medicine. There is substantial evidence indicating that propolis exhibits a broad spectrum of therapeutic (biological/pharmacological) properties such as antimicrobial, anti-oxidant, anti-inflammatory, immunomodulatory, antitumor, anticancer, anti-ulcer, hepatoprotective, and cardioprotective properties. Propolis contains more than 200-300 natural compounds. The biological/pharmacological activities of propolis depend on the presence of a large number of polyphenols, mainly flavonoids (flavonoid aglycones), aromatic acids, phenolic acid esters (caffeates and ferulates), triterpenes, diterpenic acids and lignanes. The chemical composition and beneficial properties of propolis vary depending on the plant source, geographic origin and collection time. Present overview is an attempt to discuss the molecular mechanism(s) underlying the diverse biological effects of propolis.