Radical-scavenging activity and phenolic constituents of propolis from different regions of Argentina.

Propolis is a resinous substance collected by honeybees from various plant sources. The composition of propolis depends on the type of vegetation and the area of collection. We examined the radical-scavenging activity of propolis from the following regions of Argentina: Mendoza, Rio Negro, La Pampa, and Entre Rios. Ethanol extracts of propolis (EEP) were prepared and their 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities were evaluated. Furthermore, the major constituents in EEP were identified by HPLC with photodiode array (PDA) detection, and each component was quantitatively analysed. Almost all of the propolis samples, except La Pampa, had radical-scavenging activity. Propolis with strong radical-scavenging activity contained large amounts of antioxidative compounds, such as caffeic acid, ferulic acid and caffeic acid phenethyl ester.