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Design of an Antioxidant Nitrone Scaffold Based on Plant Pigments

preprint
revised on 28.01.2021, 17:53 and posted on 29.01.2021, 11:24 by Amanda Capistrano Pinheiro, Rodrigo Boni Fazzi, Larissa Cerrato Esteves, Caroline Oliveira Machado, Felipe Augusto Dörr, Ernani Pinto, Yocefu Hattori, Jacinto Sa, Ana Maria Da Costa Ferreira, Erick Leite Bastos

Nitrones derived from natural antioxidants are emerging as highly specific therapeutics against various human diseases, including stroke, neurodegenerative pathologies, and cancer. However, the development of useful pseudo-natural nitrones requires the judicious choice of a secondary metabolite as the precursor. Betalains are nitrogen-containing natural pigments that exhibit marked antioxidant capacity and pharmacological properties and, hence, are ideal candidates for designing multifunctional nitrones. In this work, we describe the semisynthesis and properties of a biocompatible, antioxidant betalain-nitrone called OxiBeet. This bio-based compound is a better radical scavenger than ascorbic acid, gallic acid, and most non-phenolic antioxidants and undergoes concerted proton-coupled electron transfer. The autoxidation of OxiBeet produces a persistent nitroxide radical, which, herein, is studied via electron paramagnetic resonance spectroscopy. In addition, femtosecond transient absorption spectroscopy reveals that excited state formation is not required for the oxidation of OxiBeet. The results are compared with those obtained using betanin, a natural betalain, and pBeet, the imine analog of OxiBeet. The findings of this study will enable the development of antioxidant nitrones based on the novel N-oxide 1,7-diazaheptamethinium scaffold and betalain dyes with enhanced hydrolytic stability in aqueous alkaline media.

Funding

São Paulo Research Foundation, FAPESP, Grant 2014/22136-4

São Paulo Research Foundation, FAPESP, Grant 2019/08950-1

São Paulo Research Foundation, FAPESP, Grant 2019/06391-8

São Paulo Research Foundation, FAPESP, Grant 2019/15412-9

São Paulo Research Foundation, FAPESP, Grant 2015/18474-4

São Paulo Research Foundation, FAPESP, Grant 2013/07937-8

Brazilian National Council for Scientific and Technological Development, CNPq, Grant 301623/2019-8

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES, Finance Code 001

History

Email Address of Submitting Author

elbastos@iq.usp.br

Institution

Universidade de São Paulo

Country

Brazil

ORCID For Submitting Author

0000-0002-0592-9455

Declaration of Conflict of Interest

There are no conflicts to declare.

Version Notes

v.1. v.2. Updated version.

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ChemRxiv

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