Reduction reactivity of catecholamines and their ability to promote a Fenton reaction

• Catecholamines can reduce Fe(III) at acidic pH values up to pH 5.5.
• Fe(III) reduction by catecholamines is correlated with OH production by Fenton reaction.
• Catecholamines promote O2 reduction to H2O2 at pH near 7.0.
• Catecholamines cannot promote Fenton reactions at pH near 7.0.

Several studies have assigned catecholamines a pro-oxidant role and have therefore correlated catecholamines with the development of different pathophysiological processes. This pro-oxidant effect could be due to the Fenton reaction (i.e., Fe(II) + H2O2 → Fe(III) + OH + OH−), which is known to be utilized by catecholamines to reduce Fe(III) and O2. In this work, the ability of a few catecholamines (i.e., dopamine, epinephrine and norepinephrine) to reduce Fe(III) to Fe(II) and O2 to H2O2 and to produce OH radicals by the Fenton reaction was evaluated at different pH values. The catecholamines were observed to produce Fe(II) and H2O2 at different pH values. Therefore, OH radical production was enhanced at pH values where only Fe(III) reduction was observed. At pH values near 7.0, the catecholamines did not enhance the production of OH radicals. Instead, the catecholamines acted as antioxidants forming bis-complexes, i.e., [Fe(LH)2]+. The catecholamines sequestered iron from the reaction system and thereby prevented iron from reacting with other compounds such as H2O2.

The reduction of Fe(III) and O2 by catecholamines occurs at different pH range. Although catecholamines can produces H2O2 by their autoxidation, these compounds only promote OH radical production by Fenton reaction at pH value wherein Fe(III) is reduced. This is because OH radical production is related to initial rate of Fe(III) reduction.Figure optionsDownload as PowerPoint slide