ANTIOXIDATIVE ACTION OF THE ETHANOLIC EXTRACT AND SOME HYDROXYCOUMARINS OF FRAXINUS-ORNUS BARK

The antioxidative effectivity and strength of different concentrations of ethanolic extract from Fraxinus ornus bark, as well as of esculetin, esculin, fraxetin and fraxin during the autoxidation at 100 degrees C of kinetically pure triacylglycerols of lard (TGL) and triacylglycerols of sunflower oil (TGSO) were determined. The extract exhibited a pronounced antioxidative activity. Esculetin and fraxetin considerably retarded the process in both lipid systems, this being more significant in the less oxidizable lipid substrate (TCL). Fraxetin proved to be a more efficient and stronger inhibitor than esculetin. During the oxidation of TGSO the fraxetin caused a stronger decrease in antioxidative activity. The participation of both hydroxycoumarins in the side reactions of inhibited oxidation, which explains their kinetic behaviour, is discussed. Fraxin and esculin displayed a very weak antioxidative action.