Ethanolic and aqueous extracts of the natural compound PROPOLIS indicate substantial antiinflammatory functions as well as antibiotic activities in vitro and in vivo. The exact mode of physiological or biochemical mechanisms responsible for the medical effects, however, is all but clear. The standardization on the basis of quantitative determination of prominent components of these extracts have been substituted recently by simple biochemical model reactions including photodynamic properties. In this communication we report on the inhibitory activity of an aqueous extract of propolis on the enzyme dihydrofolate reductase. This activity may at least partially be due to the content of caffeic acid, as revealed by HPLC chromatography and comparative activity tests of representative ingredients of the propolis extract. This result may explain some of the protective functions of propolis, similar to those shown for several “non-steroidal antiinflammatory drugs”, NSAIDs.
