IN-VITRO ANTI-OXIDATIVE AND PRO-OXIDATIVE EFFECTS OF NATURAL POLYPHENOLS

The anti- and pro-oxidative effects of phenolic compounds and antioxid ants were studied in two different in vitro model systems utilizing et hyl linoleate and 2'-deoxyguanosine (2'-dG) as oxidative substrates, a nd a Fenton reaction (H2O2, Fe2+) to initiate oxidation. Oxidation of the biomolecules in both model systems exhibited dose dependency. In t he 2'-dG assay, oxidation was closely related to H2O2 generation, whic h occurred during autoxidation of the phenolics. Hydroxylating activit y was greatly enhanced by Mn2+ and Cu2+, but not by Zn2+ or Co2+. Ethy l Linoleate peroxidation was inhibited by low concentrations of catech ol, quercitin, and instant coffee. However, peroxidation was promoted by high concentrations of the same compounds, probably by recycling of chelated inactive Fe3+ to the active Fe2+ state.