Anti- and Prooxidative Properties of Gallic Acid in Fenton-Type Systems

• Published in: Journal of agricultural and food chemistry 2002-10, Vol.50 (22), p.6313-6317
• Main Authors: Strlič, Matija, Radovič, Tanja, Kolar, Jana, Pihlar, Boris
• Format: Article
• Language: English
• Subjects: Antioxidants - metabolism; Biological and medical sciences; Food additives; Food industries; Free Radical Scavengers - metabolism; Fundamental and applied biological sciences. Psychology; Gallic Acid - metabolism; General aspects; General pharmacology; Hydrogen Peroxide - metabolism; Hydrogen-Ion Concentration; Hydroxyl Radical - metabolism; Iron - metabolism; Iron Chelating Agents - metabolism; Kinetics; Medical sciences; Oxidants - metabolism; Oxidation-Reduction; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Temperature
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf025636j

The anti- and prooxidative properties of gallic acid in Fenton-type systems containing H2O2 and Fe(III) were examined in pH 3−10 reaction media and at reaction temperatures of 20−50 °C. Although it is a free radical scavenger, gallic acid may exhibit prooxidative properties, as it promotes the production of hydroxyl radicals due to iron chelation. The overall effect is prooxidative if the ratio of the concentrations of gallic acid and Fe(III) in the reaction medium is smaller than 2. If the ratio is greater than 2, the overall effect of gallic acid presence is antioxidative due to free radical scavenging properties. The dependence of rates and of apparent activation energies of gallic acid consumption on pH in Fenton-type systems was also examined, and it is concluded that the rate-determining steps in acidic and alkaline media are different, the overall rate of gallic acid consumption being lowest at pH 7. Keywords: Phenolic antioxidants; transition metals; iron chelation; free radicals; Fenton reaction