Inhibition by Salix- extracts and Phytodolor of copper-catalyzed oxidative destruction

Oxidation of low density lipoprotein (LDL) by copper ions is strongly inhibited by different aqueous extracts (Salix spec (SE); Fraxinus-Dolidago-Populus (Phytodolor)(PD) in a concentration range between 4 and 7 micrograms/ml. 10 to 50 microM salicylic acid (SA) stimulate LDL-oxidation whereas higher concentrations (10 to 500 micromM) showed no effect. Likewise ethene release from 2-keto-4-methylthiobutyrate (KMB) is strongly inhibited by the above extracts in a reaction driven by dihydroxyfumarate (DHF) in the presence of copper ions. This system may represent some features of the diabetic situation where DHF as an endiole may stand for certain Amadori products. In order to find out whether the inhibitory effects are due to copper chelation we tested the copper-dependent conversion of photodynamic ethane release from alpha-linolenic acid into ethene formation. Copper chelation is apparently only partially involved in inhibition of copper-dependent oxidations and only at a certain concentration of extracts from salix spec (SE) or extracts from Fraxinus-Solidago-Populus (Phytodolor)(PD).