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Hydrogen Atom Transfer from HOO. to ortho-Quinones Explains the Antioxidant Activity of Polydopamine.


ABSTRACT: Melanins are stable and non-toxic biomaterials with a great potential as chemopreventive agents for diseases connected with oxidative stress, but the mechanism of their antioxidant action is unclear. Herein, we show that polydopamine (PDA), a well-known synthetic melanin, becomes an excellent trap for alkylperoxyl radicals (ROO. , typically formed during autoxidation of lipid substrates) in the presence of hydroperoxyl radicals (HOO. ). The key reaction explaining this peculiar antioxidant activity is the reduction of the ortho-quinone moieties present in PDA by the reaction with HOO. . This reaction occurs via a H-atom transfer mechanism, as demonstrated by the large kinetic solvent effect of the reaction of a model quinone (3,5-di-tert-butyl-1,2-benzoquinone) with HOO. (k=1.5×107 and 1.1×105  M-1  s-1 in PhCl and MeCN). The chemistry disclosed herein is an important step to rationalize the redox-mediated bioactivity of melanins and of quinones.

SUBMITTER: Guo Y 

PROVIDER: S-EPMC8362028 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature

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Hydrogen Atom Transfer from HOO<sup>.</sup> to ortho-Quinones Explains the Antioxidant Activity of Polydopamine.

Guo Yafang Y   Baschieri Andrea A   Mollica Fabio F   Valgimigli Luca L   Cedrowski Jakub J   Litwinienko Grzegorz G   Amorati Riccardo R  

Angewandte Chemie (International ed. in English) 20210604 28


Melanins are stable and non-toxic biomaterials with a great potential as chemopreventive agents for diseases connected with oxidative stress, but the mechanism of their antioxidant action is unclear. Herein, we show that polydopamine (PDA), a well-known synthetic melanin, becomes an excellent trap for alkylperoxyl radicals (ROO<sup>.</sup> , typically formed during autoxidation of lipid substrates) in the presence of hydroperoxyl radicals (HOO<sup>.</sup> ). The key reaction explaining this pecu  ...[more]

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