Mechanism of the structural transformations of anthocyanins in acidic media

Brouillard, Raymond; Dubois, Jacques-Émile

doi:10.1021/ja00447a012

Cited by 379 publications

(268 citation statements)

References 2 publications

Supporting

Mentioning

249

Contrasting

Unclassified

Order By: Relevance

“…(B) DMBQ (ii) and peonidin (iii) enter the parasite cells, possibly by nonselective diffusion (Shann and Blum, 1987). Peonidin is drawn in one of several possible conformations (Brouillard and Cheminat, 1982). (C) The p-benzoquinone motive (iv) is reduced by a single electron to a free radical semiquinone (v) by the action of QR1.…”

Section: Discussionmentioning

confidence: 99%

A Single-Electron Reducing Quinone Oxidoreductase Is Necessary to Induce Haustorium Development in the Root Parasitic Plant Triphysaria

et al. 2010

View full text Add to dashboard Cite

Parasitic plants in the Orobanchaceae develop haustoria in response to contact with host roots or chemical haustoriainducing factors. Experiments in this manuscript test the hypothesis that quinolic-inducing factors activate haustorium development via a signal mechanism initiated by redox cycling between quinone and hydroquinone states. Two cDNAs were previously isolated from roots of the parasitic plant Triphysaria versicolor that encode distinct quinone oxidoreductases. QR1 encodes a single-electron reducing NADPH quinone oxidoreductase similar to z-crystallin. The QR2 enzyme catalyzes two electron reductions typical of xenobiotic detoxification. QR1 and QR2 transcripts are upregulated in a primary response to chemical-inducing factors, but only QR1 was upregulated in response to host roots. RNA interference technology was used to reduce QR1 and QR2 transcripts in Triphysaria roots that were evaluated for their ability to form haustoria. There was a significant decrease in haustorium development in roots silenced for QR1 but not in roots silenced for QR2. The infrequent QR1 transgenic roots that did develop haustoria had levels of QR1 similar to those of nontransgenic roots. These experiments implicate QR1 as one of the earliest genes on the haustorium signal transduction pathway, encoding a quinone oxidoreductase necessary for the redox bioactivation of haustorial inducing factors.

show abstract

Section: Discussionmentioning

confidence: 99%

A Single-Electron Reducing Quinone Oxidoreductase Is Necessary to Induce Haustorium Development in the Root Parasitic Plant Triphysaria

et al. 2010

View full text Add to dashboard Cite

show abstract

“…[12][13][14][15] At physiological pH values, the dominant form of anthocyanins is typically the hemiacetal (B), in equilibrium with minor amounts of the isomeric chalcones (C E and C Z ). 3 In the last few years, substantial progress has been made in understanding several aspects of the complex chemistry and photochemistry of anthocyanins. Many of the factors that affect the ground state equilibria of anthocyanins (Scheme 1) are much better understood and these equilibria (and hence anthocyanin color) can be manipulated in micellar media by appropriate choice of the detergent.…”

Section: Introductionmentioning

confidence: 99%

“…1,2 Interest in the anthocyanins stems from the fact that they are omnipresent in our diet, exhibit unusual chemical and photochemical properties, [3][4][5][6][7][8][9] and have potential for application as food dyes 1 and antioxidant additives. 10,11 The basic chromophore of anthocyanins is the 7-hydroxyflavylium ion ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

A computational study of substituted flavylium salts and their quinonoidal conjugate-bases: S0 -> S1 electronic transition, absolute pKa and reduction potential calculations by DFT and semiempirical methods

Freitas¹,

Shimizu²,

Dias³

et al. 2007

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

As transições eletrônicas para os cátions flavílio e bases quinonoidais de dezessete sais deste cátion foram estudadas nos níveis semiempírico e DFT (teoria do funcional da densidade). O efeito do solvente nos espectros eletrônicos foi incluído pelo Modelo Contínuo Polarizado, PCM. As transições eletrônicas de menor energia foram assinaladas como transições HOMO→LUMO. Ambos os níveis de teoria forneceram bons resultados para as transições eletrônicas dos cátions flavílio, enquanto apenas os cálculos por TDDFT-PCM puderam ser empregados para as transições das bases quinonoidais. Foram feitos cálculos de pK a absoluto para nove sais de flavílio em nível DFT. Os valores de pK a calculados pela nossa parametrização do PCM forneceram resultados excelentes, com um desvio médio absoluto de menos de meia unidade de pK a . Foram calculados por DFT potenciais de redução para cinco cátions flavílio. Os resultados teóricos encontrados ficaram em boa concordância com os resultados experimentais após a correção de um desvio sistemático.The electronic transitions for flavylium cations and quinonoidal bases of 17 substituted flavylium salts have been studied at semiempirical and DFT (density functional theory) levels. Solvent effect on electronic spectra was included by Polarizable Continuum Model, PCM. We assigned longest-wavelength absorption maxima to HOMO→LUMO transition. Both levels of theory gave good results for electronic transitions of flavylium cations whereas only TDDFT-PCM calculations could be used for electronic transitions of their quinonoidal bases. We also performed absolute pK a calculations of nine flavylium salts at DFT level. The pK a calculated values by our PCM parameterization gave excellent results with mean absolute deviation less than a half of one pK a unit. One-electron reduction potentials were carried out for 5 flavylium cations at DFT level. The theoretical results found were in good agreement with experimental values after adjustment for a systematic deviation.Keywords: flavylium salts, anthocyanins, quinonoidal base, pK a calculation, time dependent-DFT IntroductionAnthocyanins constitute the major red and purple pigments in plants and can be found in fruits, flowers and leaves. 1,2 Interest in the anthocyanins stems from the fact that they are omnipresent in our diet, exhibit unusual chemical and photochemical properties, [3][4][5][6][7][8][9] and have potential for application as food dyes 1 and antioxidant additives. 10,11 The basic chromophore of anthocyanins is the 7-hydroxyflavylium ion (Figure 1). In nature, the flavylium ion typically has hydroxyl substituents at positions 3 (always glycosylated) and 5 (occasionally glycosylated) and the phenyl or B-ring has one or more hydroxyl or methoxy substituents. 1 The colors of natural and synthetic anthocyanins range from yellow to purple, depending on the degree of substitution of the 7-hydroxyflavylium ion chromophore. Rationalization of the chemical and photochemical properties of anthocyanins is complicated by the fact that, in aqueous solu...

show abstract

“…As transformações estruturais que provocam tais mudanças de cor em função do pH foram também descritas previamente por Brouillard e colaboradores 11,12 e por Epp 13 .…”

Section: Introductionunclassified

Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas

2007

View full text Add to dashboard Cite

Recebido em 3/1/06; aceito em 28/7/06; publicado na web em 26/3/07 SPECTROPHOTOMETRIC TITRATIONS OF ACID-BASE SYSTEMS USING FLOWER EXTRACTS CONTAINIG ANTHOCYANINS. Considering the attraction of the students' attention by the changes in the colors of vegetable crude extracts caused by the variation of the pH of the medium, the use of these different colors in order to demonstrate principles of spectrophotometric acid-base titrations using the crude extracts as indicators is proposed. The experimental setup consisted of a simple spectrophotometer, a homemade flow cell and a pump to propel the fluids along the system. Students should be stimulated to choose the best wavelength to monitor the changes in color during the titration. Since the pH of the equivalence point depends on the system titrated, the wavelength must be properly chosen to follow these changes, demonstrating the importance of the correct choice of the indicator. When compared with the potentiometric results, errors as low as 2% could be found using Rhododendron simsii (azalea) or Tibouchina granulosa (Glory tree, quaresmeira) as sources of the crude extracts.Keywords: acid-base chemistry; instrumental methods; spectrophotometric titrations. INTRODUÇÃOO uso de corantes naturais no ensino médio e superior, principalmente de química geral e analítica, tem sido proposto freqüen-temente. As principais vantagens são relacionadas com a atração do interesse dos estudantes para o conteúdo abordado, devido à coloração das espécies químicas contidas nos tecidos vegetais e suas mudanças de cor em função do pH 1,2 . Some-se a isto o fato de usar algo presente no cotidiano dos estudantes para esta finalidade, ligando a química ao seu dia-a-dia.Neste contexto, os corantes foram propostos para demonstração de conceitos de pH 1-3 , como indicadores em titulações ácido-base, com detecção visual do ponto final 4 , para demonstração de fundamentos de cromatografia em camada delgada 5 e aplicação em méto-dos óticos de análise 6 , de princípios de análise em fluxo 7 e na determinação de sulfito em vinhos 8 e de nitrito em águas 9 .As mudanças na coloração de extratos de tecidos vegetais foram abordadas inicialmente por Geissman 10 , que as atribuiu às antocianinas. As antocianinas são as formas glicosiladas das antocianidinas que, por sua vez, são compostos da classe dos flavonóides e que conferem coloração azul ou vermelha aos tecidos vegetais 1,10 .As transformações estruturais que provocam tais mudanças de cor em função do pH foram também descritas previamente por Brouillard e colaboradores 11,12 e por Epp 13 .As estrutras químicas das antocianinas e as mudanças estruturais, que ocorrem com a variação do pH e provocam as mudanças de cor, podem ser encontradas nas referências citadas acima. Uma discussão mais aprofundada sobre esta classe interessante de flavonóides pode ser encontrada no trabalho de Timberlake e Bridle 14 .Neste artigo, propõe-se o aproveitamento da mudança de cor de extratos brutos de espécies vegetais contendo antocianinas para a detecção espectrof...

show abstract

Mechanism of the structural transformations of anthocyanins in acidic media

Cited by 379 publications

References 2 publications

A Single-Electron Reducing Quinone Oxidoreductase Is Necessary to Induce Haustorium Development in the Root Parasitic Plant Triphysaria

A Single-Electron Reducing Quinone Oxidoreductase Is Necessary to Induce Haustorium Development in the Root Parasitic Plant Triphysaria

A computational study of substituted flavylium salts and their quinonoidal conjugate-bases: S0 -> S1 electronic transition, absolute pKa and reduction potential calculations by DFT and semiempirical methods

Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas

Contact Info

Product

Resources

About