Antioxidant activity of caffeic acid against iron-induced free radical generation - a chemical approach
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2015-06
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Caffeic acid (CA) is a phenolic compound widely found in coffee beans with known beneficial
effects in vivo. Many studies showed that CA has anti-inflammatory, anti-mutagenic, antibacterial
and anti-carcinogenic properties, which could be linked to its antioxidant activity.
Taking in consideration the reported in vitro antioxidant mechanism of other polyphenols,
our working hypothesis was that the CA antioxidant activity could be related to its metal-chelating
property. With that in mind, we sought to investigate the chemical antioxidant mechanism
of CA against in vitro iron-induced oxidative damage under different assay conditions.
CA was able to prevent hydroxyl radical formation promoted by the classical Fenton reaction,
as determined by 2-deoxyribose (2-DR) oxidative degradation and DMPO hydroxylation.
In addition to its ability to prevent hydroxyl radical formation, CA had a great inhibition
of membrane lipid peroxidation. In the lipid peroxidation assays CA acted as both metalchelator
and as hydrogen donor, preventing the deleterious action promoted by lipid-derived
peroxyl and alkoxyl radicals. Our results indicate that the observed antioxidant effects
were mostly due to the formation of iron-CA complexes, which are able to prevent 2-DR oxidation
and DMPO hydroxylation. Noteworthy, the formation of iron-CA complexes and prevention
of oxidative damage was directly related to the pH of the medium, showing better
antioxidant activity at higher pH values. Moreover, in the presence of lipid membranes the
antioxidant potency of CA was much higher, indicating its enhanced effectiveness in a hydrophobic
environment. Overall, our results show that CA acts as an antioxidant through an
iron chelating mechanism, preventing the formation of free hydroxyl radicals and, therefore,
inhibiting Fenton-induced oxidative damage. The chemical properties of CA described here
—in association with its reported signaling effects—could be an explanation to its beneficial
effects observed in vivo.
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GENARO-MATTOS, Thiago C.; MAURÍCIO, Ângelo Q.; RETTORI, Daniel; ALONSO, Antonio; HERMES-LIMA, Marcelo. Antioxidant activity of caffeic acid against iron-induced free radical generation - a chemical approach. Plos One, San Francisco, v. 10, n. 6, e0129963, June 2015.