COX-1 and COX-2 inhibitory activity of extracts produced from organic waste materials

The aim of the European project SAFEWASTES is the processing of organic waste materials from the food, feed and pharmaceutical industry to high added value products of preventive or therapeutic potential for livestock or humans. As a part of the in vitro testings performed within this project, we screened aqueous, hydroethanolic and lipophilic extracts from 12 different waste materials for their inhibitory activity against the enzymes COX-1 and COX-2, which catalyze the first two steps of prostaglandin formation in the arachidonic acid cascade. From the 30 extracts tested up to now, a lipophilic extract from preextracted willow bark (Salix sp.) showed the highest inhibitory activity against the two isoenzymes, with IC₅₀ values of 4.72µg/mL against COX-1 and 1.86µg/mL against COX-2. The aqueous extract of this material was inactive, and the ethanolic extract only showed moderate activity at the screening concentration of 20µg/mL.

In order to find out, whether the high activity of the extract is caused by the presence of high amounts of free fatty acids, which are known to possess a certain COX-1- and a quite strong COX-2 inhibitory activity in vitro, the free fatty acids in the extract were quantified by GC-FID. 3.02% linoleic acid, 0.95% oleic acid, 2.08% palmitic acid and 0.12% stearic acid were found in the extract. Comparison of the fatty acid concentration present in the assay mixture at the extract's IC₅₀ with the IC₅₀ values of the pure fatty acids [1] led to the conclusion that the free fatty acids do not significantly contribute to the COX-1 and COX-2 inhibitory activity of this extract.

The bioassay guided fractionation of the extract in order to isolate the active principle is under progress.

Acknowledgements: This project is supported by funding under the Sixth Research Framework Programme of the European Union.

Reference: 1. Reininger, E.A., Bauer, R. (2006), Phytomedicine 13: 164–169.