Comparison of the effect of N-methyl and N-aryl groups on the hydrolytic stability and electronic properties of betalain dyes

Autor(es)

Pioli, Renan Moraes ; Mattioli, Renan Rodini ; Esteves, Larissa Cerrato ; Dochev, Stefan ; Bastos, Erick Leite

• Tipo de documento: Artigo Científico
• Fonte: DYES AND PIGMENTS; v. 183, p. 7-pg., 2020-12-01.

Resumo

Betalains are antioxidant secondary metabolites that emerged as safe color additives for food and cosmetics, fluorescent dyes, and redox mediators. Herein, we describe the semisynthesis of N-methyl phenylbetalain (mepBeets) and N-aryl phenylbetalain (dipBeets) dyes and compare the effect of the structure on their hydrolytic stability and electronic properties. Eight model compounds were semisynthesized by coupling betalamic acid with either N-methyl anilines or N-aryl anilines in ethyl acetate using p-toluenesulfonic acid as catalyst. The presence of electron-withdrawing substituents in the aryl moiety of mepBeets and dipBeets results in faster hydrolysis, lower anodic potentials and increased fluorescence quantum yields compared to the corresponding unsubstituted parent compounds. The results are rationalized by considering the charge distribution in the 1,7-diazaheptamethinium chromophore and are useful for the development of new hydrolytically stable betalain dyes with tunable redox and optical properties. (AU)

• Processo FAPESP: 14/22136-4 - Uso de solventes verdes e suas misturas na otimização de processos químicos
• Beneficiário: Omar Abou El Seoud
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 16/21445-9 - Betalaínas: relações estrutura-propriedade
• Beneficiário: Erick Leite Bastos
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 17/20133-6 - Efeito da N-metilação sobre a estabilidade hidrolítica e fluorescência de sondas betalaínicas
• Beneficiário: Renan Rodini Mattioli
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 19/06391-8 - Caracterização fotofísica e potencial anti-inflamatório de betalaínas
• Beneficiário: Erick Leite Bastos
• Modalidade de apoio: Auxílio à Pesquisa - Regular