INACTIVATION OF OXYGEN RADICALS BY DIETARY PHENOLIC-COMPOUNDS IN ANTICARCINOGENESIS

Hydroxylated and polyhydroxylated aromatic and heterocyclic compounds may have antioxidant and anticarcinogenic properties. Whether an antioxidant is an anticarcinogen may depend on its efficacy as an oxygen radical (peroxyl, alkoxyl, superoxide, hydroxyl) inactivator and inhibitor. Location, concentration in situ, reaction kinetics (rate constants), energetics (redox potentials), and products (intermediates and final) contribute to the efficacy of an antioxidant. The kinetics and energetics of an antioxidant are governed by the type and position of the substituents. The rate constant for the reaction of an antioxidant and an oxy radical depends on the type of radical. In general, the reactivity of a radical decreases in the following order: hydroxyl > alkoxyl > peroxyl > superoxide. One-electron oxidation potential of an antioxidant at pH 7, E(7), can be calculated from the Hammett correlation using Brown substituent constants.