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Anthocyanins: Chemistry and Bioactivity

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Bioactives and Nutraceuticals".

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 21035

Special Issue Editor

LAQV–REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, 4169-007 Porto, Portugal
Interests: agri-food wastes; lignin; color stabilization; anthocyanins; food science
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Anthocyanins are a class of phenolic compounds responsible for a great diversity of colours (from red to blue) found in nature, especially flowers and fruits, and some processed products such as, juices and red wines. Over the years, numerous biologic studies have demonstrated their potential health benefits to Humans, specially related to the antioxidant properties of anthocyanins. In aqueous solution, these pigments exist as different species: flavylium cation, neutral and anionic quinoidal base, hemiketal form, cis- and trans-chalcone forms in equilibrium. Besides pH, anthocyanins stability is also affected by light, temperature and exposure to oxygen which has been limiting their use in food and cosmetic matrices as colorants and nutraceutics. Several strategies have been reported in the literature regarding the stabilization of these pigments towards their application into different matrices. This includes, interaction with different compounds including polymers and the chemical/enzymatic transformation into more stable pigments.

We invite researchers to contribute either with original research or review articles focusing on, but not limited to: i) chemical transformation of anthocyanins towards the production of more stabilized structures with appealing chromatic features; ii) stabilization of anthocyanin using original approaches; iii) mechanism of action in improving human nutrition; iv) bioactivity (bioavailability, metabolites, enzymes inhibition, anti-proliferative and anti-bacterial activities).

Dr. Joana Oliveira
Guest Editor

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Keywords

  • anthocyanins
  • chemical and enzymatic transformation
  • physical-chemical features
  • anthocyanin in human nutrition
  • enzymes interactions
  • anthocyanins bioavailability
  • anti-proliferative activity
  • anti-bacterial activity

Published Papers (7 papers)

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Research

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17 pages, 1970 KiB  
Article
The Role of Anthocyanins, Deoxyanthocyanins and Pyranoanthocyanins on the Modulation of Tyrosinase Activity: An In Vitro and In Silico Approach
Int. J. Mol. Sci. 2021, 22(12), 6192; https://doi.org/10.3390/ijms22126192 - 08 Jun 2021
Cited by 7 | Viewed by 2334
Abstract
Tyrosinase is the central enzyme involved in the highly complex process of melanin formation, catalyzing the rate-limiting steps of this biosynthetic pathway. Due to such a preponderant role, it has become a major target in the treatment of undesired skin pigmentation conditions and [...] Read more.
Tyrosinase is the central enzyme involved in the highly complex process of melanin formation, catalyzing the rate-limiting steps of this biosynthetic pathway. Due to such a preponderant role, it has become a major target in the treatment of undesired skin pigmentation conditions and also in the prevention of enzymatic food browning. Numerous phenolic-based structures from natural sources have been pointed out as potential tyrosinase inhibitors, including anthocyanins. The aim of the present study was to individually assess the tyrosinase inhibitory activity of eight purified compounds with a variable degree of structural complexity: native anthocyanins, deoxyanthocyanins, and pyranoanthocyanins. The latter two, the groups of anthocyanin-related compounds with enhanced stability, were tested for the first time. Compounds 1 to 4 (luteolinidin, deoxymalvidin, cyanidin-, and malvidin-3-O-glucoside) revealed to be the most effective inhibitors, and further kinetic studies suggested their inhibition mechanism to be of a competitive nature. Structure–activity relationships were proposed based on molecular docking studies conducted with mushroom tyrosinase (mTYR) and human tyrosinase-related protein 1 (hTYRP1) crystal structures, providing information about the binding affinity and the different types of interactions established with the enzyme’s active center which corroborated the findings of the inhibition and kinetic studies. Overall, these results support the applicability of these compounds as pigmentation modulators. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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15 pages, 2525 KiB  
Article
Acylated Anthocyanins from Red Cabbage and Purple Sweet Potato Can Bind Metal Ions and Produce Stable Blue Colors
Int. J. Mol. Sci. 2021, 22(9), 4551; https://doi.org/10.3390/ijms22094551 - 27 Apr 2021
Cited by 10 | Viewed by 3378
Abstract
Red cabbage (RC) and purple sweet potato (PSP) are naturally rich in acylated cyanidin glycosides that can bind metal ions and develop intramolecular π-stacking interactions between the cyanidin chromophore and the phenolic acyl residues. In this work, a large set of RC and [...] Read more.
Red cabbage (RC) and purple sweet potato (PSP) are naturally rich in acylated cyanidin glycosides that can bind metal ions and develop intramolecular π-stacking interactions between the cyanidin chromophore and the phenolic acyl residues. In this work, a large set of RC and PSP anthocyanins was investigated for its coloring properties in the presence of iron and aluminum ions. Although relatively modest, the structural differences between RC and PSP anthocyanins, i.e., the acylation site at the external glucose of the sophorosyl moiety (C2-OH for RC vs. C6-OH for PSP) and the presence of coordinating acyl groups (caffeoyl) in PSP anthocyanins only, made a large difference in the color expressed by their metal complexes. For instance, the Al3+-induced bathochromic shifts for RC anthocyanins reached ca. 50 nm at pH 6 and pH 7, vs. at best ca. 20 nm for PSP anthocyanins. With Fe2+ (quickly oxidized to Fe3+ in the complexes), the bathochromic shifts for RC anthocyanins were higher, i.e., up to ca. 90 nm at pH 7 and 110 nm at pH 5.7. A kinetic analysis at different metal/ligand molar ratios combined with an investigation by high-resolution mass spectrometry suggested the formation of metal–anthocyanin complexes of 1:1, 1:2, and 1:3 stoichiometries. Contrary to predictions based on steric hindrance, acylation by noncoordinating acyl residues favored metal binding and resulted in complexes having much higher molar absorption coefficients. Moreover, the competition between metal binding and water addition to the free ligands (leading to colorless forms) was less severe, although very dependent on the acylation site(s). Overall, anthocyanins from purple sweet potato, and even more from red cabbage, have a strong potential for development as food colorants expressing red to blue hues depending on pH and metal ion. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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11 pages, 1310 KiB  
Article
Polyacylated Anthocyanins in Bluish-Purple Petals of Chinese Bellflower, Platycodon grandiflorum
Int. J. Mol. Sci. 2021, 22(8), 4044; https://doi.org/10.3390/ijms22084044 - 14 Apr 2021
Cited by 8 | Viewed by 1881
Abstract
The bluish-purple petals of Chinese bellflower, Platycodon grandiflorum (kikyo in Japanese), contain platyconin (1) as the major anthocyanin. Platyconin (1) is a polyacylated anthocyanin with two caffeoyl residues at the 7-position, and its color is stable in a diluted, [...] Read more.
The bluish-purple petals of Chinese bellflower, Platycodon grandiflorum (kikyo in Japanese), contain platyconin (1) as the major anthocyanin. Platyconin (1) is a polyacylated anthocyanin with two caffeoyl residues at the 7-position, and its color is stable in a diluted, weakly acidic aqueous solutions. HPLC analysis of the fresh petal extract showed the presence of several minor pigments. Photo-diode array detection of minor pigments suggested that some of these were polyacylated anthocyanins. To establish the relationship between structure and stability of the acylated anthocyanins and to obtain information on their biosynthetic pathways, minor pigments were isolated from the petals, and their structures were determined by MS and NMR analyses. Four known (25) and three new anthocyanins (68) were identified, which contained a delphinidin chromophore, and four of these (58) were diacylated anthocyanins, in which the acyl-glucosyl-acyl-glucosyl chain was attached at the 7-O-position of the delphinidin chromophore. These diacylated anthocyanins exhibited a bluish-purple color at pH 6, which was stable for more than a week. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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18 pages, 20531 KiB  
Article
Evolution of Flavylium-Based Color Systems in Plants: What Physical Chemistry Can Tell Us
Int. J. Mol. Sci. 2021, 22(8), 3833; https://doi.org/10.3390/ijms22083833 - 07 Apr 2021
Cited by 14 | Viewed by 2408
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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15 pages, 4029 KiB  
Article
BrLETM2 Protein Modulates Anthocyanin Accumulation by Promoting ROS Production in Turnip (Brassica rapa subsp. rapa)
Int. J. Mol. Sci. 2021, 22(7), 3538; https://doi.org/10.3390/ijms22073538 - 29 Mar 2021
Cited by 2 | Viewed by 2646
Abstract
In ‘Tsuda’ turnip, the swollen root peel accumulates anthocyanin pigments in a light-dependent manner, but the mechanism is unclear. Here, mutant g120w which accumulated extremely low levels of anthocyanin after light exposure was identified. Segregation analysis showed that the anthocyanin-deficient phenotype was controlled [...] Read more.
In ‘Tsuda’ turnip, the swollen root peel accumulates anthocyanin pigments in a light-dependent manner, but the mechanism is unclear. Here, mutant g120w which accumulated extremely low levels of anthocyanin after light exposure was identified. Segregation analysis showed that the anthocyanin-deficient phenotype was controlled by a single recessive gene. By using bulked-segregant analysis sequencing and CAPS marker-based genetic mapping analyses, a 21.6-kb region on chromosome A07 was mapped, in which a calcium-binding EF hand family protein named BrLETM2 was identified as the causal gene. RNA sequencing analysis showed that differentially expressed genes (DEGs) between wild type and g120w in light-exposed swollen root peels were enriched in anthocyanin biosynthetic process and reactive oxygen species (ROS) biosynthetic process GO term. Furthermore, nitroblue tetrazolium (NBT) staining showed that the ROS level decreased in g120w mutant. Anthocyanins induced by UV-A were abolished by the pre-treatment of seedlings with DPI (an inhibitor of nicotinamide adenine nucleoside phosphorylase (NADPH) oxidase) and decreased in g120w mutant. These results indicate that BrLETM2 modulates ROS signaling to promote anthocyanin accumulation in turnip under UV-A and provides new insight into the mechanism of how ROS and light regulate anthocyanin production. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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16 pages, 8768 KiB  
Article
Apoptotic Effects of Anthocyanins from Vitis coignetiae Pulliat Are Enhanced by Augmented Enhancer of the Rudimentary Homolog (ERH) in Human Gastric Carcinoma MKN28 Cells
Int. J. Mol. Sci. 2021, 22(6), 3030; https://doi.org/10.3390/ijms22063030 - 16 Mar 2021
Cited by 4 | Viewed by 1910
Abstract
Evidence suggests that augmented expression of a certain gene can influence the efficacy of targeted and conventional chemotherapies. Here, we tested whether the high expression of enhancer of the rudimentary homolog (ERH), which serves as a prognostic factor in some cancers, can influence [...] Read more.
Evidence suggests that augmented expression of a certain gene can influence the efficacy of targeted and conventional chemotherapies. Here, we tested whether the high expression of enhancer of the rudimentary homolog (ERH), which serves as a prognostic factor in some cancers, can influence the efficacy of anthocyanins isolated from fruits of Vitis coignetiae Pulliat, Meoru in Korea (AIMs) on human gastric cancer cells. The anticancer efficacy of AIMs was augmented in ERH-transfected MKN28 cells (E-MKN28 cells). Molecularly, ERH augmented AIM-induced caspase-dependent apoptosis by activating caspase-3 and -9. The ERH-augmented apoptotic effect was related to mitochondrial depolarization and inhibition of antiapoptotic proteins, XIAP, and Bcl-2. In addition, reactive oxygen species (ROS) generation was augmented in AIMs-treated E-MKN28 cells compared to AIMs-treated naïve MKN28 cells. In conclusion, ERH augmented AIM-induced caspase-dependent mitochondrial-related apoptosis in MKN28 cells. A decrease in expression of Bcl-2 and subsequent excessive ROS generation would be the mechanism for ERH-augmented mitochondrial-related apoptosis in AIMs-treated MKN28 cells. A decrease in expression of XIAP would be another mechanism for ERH-augmented caspase-dependent apoptosis in AIMs-treated MKN28 cells. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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Review

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25 pages, 633 KiB  
Review
Effects of Berry Anthocyanins on Cognitive Performance, Vascular Function and Cardiometabolic Risk Markers: A Systematic Review of Randomized Placebo-Controlled Intervention Studies in Humans
Int. J. Mol. Sci. 2021, 22(12), 6482; https://doi.org/10.3390/ijms22126482 - 17 Jun 2021
Cited by 21 | Viewed by 5381
Abstract
Supplementation with anthocyanins, which are a type of flavonoids mainly found in various berries, is hypothesized to be a promising approach to lower the risk of developing cognitive decline. The aim of this systematic review was to provide a comprehensive overview of dietary [...] Read more.
Supplementation with anthocyanins, which are a type of flavonoids mainly found in various berries, is hypothesized to be a promising approach to lower the risk of developing cognitive decline. The aim of this systematic review was to provide a comprehensive overview of dietary intervention trials describing effects of berry anthocyanins on cognitive performance in humans, while also addressing potential underlying mechanisms. A total of 1197 articles were identified through a systematic search, and 49 studies reporting effects on cognitive performance (n = 18), vascular function (n = 22), or cardiometabolic risk markers (n = 32) were included. Significant improvements were observed on memory, while some of the studies also reported effects on attention and psychomotor speed or executive function. Vascular function markers such as brachial artery flow-mediated vasodilation were also affected and consistent evidence was provided for the beneficial effects of berry anthocyanins on endothelial function. Finally, studies reported improvements in blood pressure, but effects on metabolic risk markers (e.g. carbohydrate and lipid metabolism) were less consistent. In conclusion, this review provides evidence for the beneficial effects of berry anthocyanins on cognitive performance as memory improved. Whether observed anthocyanin-induced improvements in vascular function and blood pressure underlie beneficial effects on cognitive performance warrants further study. Full article
(This article belongs to the Special Issue Anthocyanins: Chemistry and Bioactivity)
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