Jodko-Piórecka K, Sikora B, Kluzek M, Przybylski P, Litwinienko G. Antiradical Activity of Dopamine, L-DOPA, Adrenaline, and Noradrenaline in Water/Methanol and in Liposomal Systems.
J Org Chem 2021;
87:1791-1804. [PMID:
34871499 PMCID:
PMC8822484 DOI:
10.1021/acs.joc.1c02308]
[Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
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Catecholamines play
a crucial role in signal transduction and are
also expected to act as endogeneous antioxidants, but the mechanism
of their antioxidant action is not fully understood. Here, we describe
the impact of pH on the kinetics of reaction of four catecholamines
(L-DOPA, dopamine, adrenaline, and noradrenaline) with model 2,2-diphenyl-1-picrylhydrazyl
radical (dpph•) in methanol/water. The increase
in pH from 5.5 to 7.4 is followed by a 2 order of magnitude increase
in the rate constant, e.g., for dopamine (DA) kpH5.5 = 1,200 M–1 s–1 versus kpH7.4 = 170,000 M–1 s–1, and such rate acceleration is attributed to a fast
electron transfer from the DA anion to dpph•. We
also proved that at pH 7.0 DA breaks the peroxidation chain of methyl
linoleate in liposomes assembled from neutral and negatively charged
phospholipids. In contrast to no inhibitory effect during peroxidation
in non-ionic emulsions, in bilayers one molecule of DA traps approximately
four peroxyl radicals, with a rate constant kinh >103 M–1 s–1. Our results from a homogeneous system and bilayers prove that catecholamines
act as effective, radical trapping antioxidants with activity depending
on the ionization status of the catechol moiety, as well as microenvironment:
organization of the lipid system (emulsions vs bilayers) and interactions
of catecholamines with the biomembrane.
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