Biol. Pharm. Bull. 28(7) 1183—1186 (2005)

and to protect the beehives against outside invaders and enemies. However, bees also take advantage of its biological action. The antibacterial and antifungal properties of propolis are responsible for the lower incidence of bacteria and moulds within the hive. Propolis is a resinous substance collected from different plant sources—the main source in Europe is popular besides birch, oak, alder, willow and hazel— and contains, depending on the region of collection different polyphenolic compounds such as flavonoids, phenolic acids and their esters, fatty acids, diterpenic acids and other compounds. But just this seems to be the main problem in the application of propolis in modern medical therapy. Due to the wide variability of its chemical compositon depending on its origin the chemical standardisation is extremely difficult. On the other hand, propolis is reported to possess the incidence of contact sensivity in persons using it in external preparations, cosmetics and self treatment of various diseases. Among the substances isolated from propolis especially the caffeic acid derivatives, flavonoids and cinnamic acid caused positive allergic reactions. Propolis as a traditional remedy in folk medicine is appreciated for its antibacterial, antifungal, antiviral, anti-inflammatory and immunostimulating activities. These effects may be induced by the potent free radical scavenger activity of flavonoids and caffeic acid derivatives, which are the typical constituents of propolis of the temperate zone of Europe, Asia and North America. Reactive oxygen species (ROS) involved in energy production, regulation of cell growth and the synthesis of biological important compounds play on the other side a damaging role and can induce peroxidative degradation of biomembranes, protein modification and DNA damage. The oxidative damage by ROS has been related to different diseases like inflammatory diseases, myocardial infarction, atherosclerosis, as well as aging and cell death. Endothelial cells as an element of the vascular system seem to be a suitable target of the cytotoxicity by oxidant stress induced by hypoxanthine–xanthine oxidase. We tested the decline of human tumour cells expressing endothelial properties (ECV 304-cells) after oxidant damage by hypoxanthine–xanthine oxidase and determined the protection provided by different propolis extracts to find out, if propolis is capable of reducing toxic effects. In addition we tested the inhibitory potency of different propolis extracts against the neutrophile elastase. The serine endopeptidase elastase is of particular importance in the degradation of connective tissue and high elastase activity levels are considered to be one indicator for inflammation. The interaction of both neutrophil elastase and reactive oxygen species play a role in inflammation and cartilage degradation as well as in ischemic injuries of lung and liver. 10—12)