A carregar...
Projeto de investigação
Not Available
Financiador
Autores
Publicações
Natural and Synthetic Flavylium-Based Dyes: The Chemistry behind the Color
Publication . Cruz, Luis; Basílio, Nuno; Mateus, Nuno; De Freitas, Victor; Pina, Fernando; LAQV@REQUIMTE; DQ - Departamento de Química; ACS - American Chemical Society
Flavylium compounds are a well-known family of pigments because they are prevalent in the plant kingdom, contributing to colors over a wide range from shades of yellow-red to blue in fruits, flowers, leaves, and other plant parts. Flavylium compounds include a large variety of natural compound classes, namely, anthocyanins, 3-deoxyanthocyanidins, auronidins, and their respective aglycones as well as anthocyanin-derived pigments (e.g., pyranoanthocyanins, anthocyanin-flavan-3-ol dimers). During the past few decades, there has been increasing interest among chemists in synthesizing different flavylium compounds that mimic natural structures but with different substitution patterns that present a variety of spectroscopic characteristics in view of their applications in different industrial fields. This Review provides an overview of the chemistry of flavylium-based compounds, in particular, the synthetic and enzymatic approaches and mechanisms reported in the literature for obtaining different classes of pigments, their physical-chemical properties in relation to their pH-dependent equilibria network, and their chemical and enzymatic degradation. The development of flavylium-based systems is also described throughout this Review for emergent applications to explore some of the physical-chemical properties of the multistate of species generated by these compounds.
A Photoswitchable Chalcone-Carbohydrate Conjugate Obtained by CuAAC Click Reaction
Publication . Paulino, Micael; Pereira, Maria Manuela A.; Basílio, Nuno; DQ - Departamento de Química; LAQV@REQUIMTE; MDPI - Multidisciplinary Digital Publishing Institute
Flavylium/Chalcone-based molecular switches comprise features such as pH-gated photochromism and fluorescence properties that make them attractive for many applications, ranging from stimuli-responsive materials to photopharmacology. However, in contrast to other common photoswitches, the application of flavylium compounds in these areas remains largely unexplored. Among other possible reasons, this may be due to the lack of general strategies to attach these molecules to substrates such as polymers, nanoparticles, biomolecules, or surfaces. In this work, we have shown that a copper (I) catalyzed azide-alkyne cycloaddition (CuAAC) can be employed to obtain a chalcone conjugate. We used an isosorbide carbohydrate to demonstrate this strategy and investigated the photochemical properties of the chalcone-isosorbide conjugate. The obtained results show that the photochemical properties of this new compound are similar to other equivalent flavylium/chalcone photoswitches, confirming the feasibility of the conjugation strategy.
Host-Guest Chemosensor Ensembles based on Water-Soluble Sulfonated Calix[n]arenes and a Pyranoflavylium Dye for the Optical Detection of Biogenic Amines
Publication . Pires, Ana Sofia; Droguett Muñoz, Kevin; de Freitas, Victor; Basílio, Nuno; Cruz, Luís; DQ - Departamento de Química; LAQV@REQUIMTE; ACS - American Chemical Society
Biogenic amines (BAs) are biologically active nitrogen-containing compounds formed during the food spoilage process and are often related as key markers of food quality, safety, and freshness. Because their presence in foods at high levels can cause significant health problems, researchers have been focused on developing novel strategies and methods for early detection and capture of these analytes. Herein, water-soluble sulfonated calix[n]arene macrocycles (SC4, SC6, and SC8) and a pH-sensitive dye (4′-hydroxy-10-methylpyranoflavylium) were investigated as host-guest systems for BA sensing. The hosts were able to bind the flavylium cation of the dye with association constants of 103 to 104 M-1. The dye complexation also allowed tuning its pKa from 6.72 (free) toward high values: 7.68 (SC4), 7.79 (SC6), and 8.45 (SC8). These data were crucial to optimize the host-guest complexes as optical sensing systems for putrescine/tyramine (pH 7.2-7.6), yielding a colorimetric redshift from yellow to red. The BA sensing was also demonstrated by fluorescence quenching for the calix[n]arene/dye complexes and fluorescence recovery after the addition of BAs. 1H NMR spectroscopy was used to demonstrate the interaction mode, confirming an encapsulation-driven mechanism. Overall, these host-guest systems demonstrated great potential for the detection of BAs, one of the main key markers of food spoilage.
The Use of Flavylium Salts as Dynamic Inhibitor Moieties for Human Cb5R
Publication . Martínez-Costa, Oscar H.; Rodrigues-Miranda, Laura; Clemente, Sofia M.; Parola, António Jorge; Basílio, Nuno; Samhan-Arias, Alejandro K.; DQ - Departamento de Química; LAQV@REQUIMTE; MDPI - Multidisciplinary Digital Publishing Institute
Cytochrome b5 reductase (Cb5R) is a flavoprotein that participates in the reduction of multiple biological redox partners. Co-localization of this protein with nitric oxide sources has been observed in neurons. In addition, the generation of superoxide anion radical by Cb5R has been observed. A search for specific inhibitors of Cb5R to understand the role of this protein in these new functions has been initiated. Previous studies have shown the ability of different flavonoids to inhibit Cb5R. Anthocyanins are a subgroup of flavonoids responsible for most red and blue colors found in flowers and fruits. Although usually represented by the flavylium cation form, these species are only stable at rather acidic pH values (pH ≤ 1). At higher pH values, the flavylium cation is involved in a dynamic reaction network comprising different neutral species with the potential ability to inhibit the activities of Cb5R. This study aims to provide insights into the molecular mechanism of interaction between flavonoids and Cb5R using flavylium salts as dynamic inhibitors. The outcome of this study might lead to the design of improved specific enzyme inhibitors in the future.
Evolution of flavylium‐based color systems in plants
Publication . Pina, Fernando; Alejo‐armijo, Alfonso; Clemente, Adelaide; Mendoza, Johan; Seco, André; Basílio, Nuno; Parola, António Jorge; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
Anthocyanins are the basis of the color of angiosperms, 3‐deoxyanthocyanins and sphagnorubin play the same role in mosses and ferns, and auronidins are responsible for the color in liverworts. In this study, the color system of cyanidin‐3‐O‐glucoside (kuromanin) as a representative compound of simpler anthocyanins was fully characterized by stopped flow. This type of anthocyanin cannot confer significant color to plants without intra‐ or intermolecular interactions, complexation with metals or supramolecular structures as in Commelina communis. The anthocyanin’s color system was compared with those of 3‐deoxyanthocyanins and riccionidin A, the aglycone of auronidins. The three systems follow the same sequence of chemical reactions, but the respective thermodynamics and kinetics are dramatically different.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
CEEC IND 2017
Número da atribuição
CEECIND/00466/2017/CP1462/CT0013