The identification of species proves thus be difficult because of subtle structural changes, being necessary for this purpose to apply [ 38 ] complementary techniques. Anthocyanins may be forming part of complexes, may be present in matrices of a complex nature and may appear in distinct equilibrium forms [ 30 , 32 , 34 ], depending of the pH of the medium.
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Acid dissociation, rate constant and tautomerization constants are of great importance in the analysis of bioactive compounds and in the interpretation of their mechanisms of action. Time-consuming processes are involved [ ] in the isolation, purification and determination of the structures of anthocyanins, which must be accomplished with care. However, there is no universal sample pretreatment technique applicable to all kind of samples. The primary steps required, sampling, sample preservation and sample preparation, are not always properly documented [ ] in the analytical literature.
A number of strategies are used [ 37 , , ] for the characterization of phenolic samples in plant materials. In any case extraction techniques and semipreparative isolation methods are usually applied prior to the separation and quantification steps. After the first operations of drying and of powdering the plant material, it follows [ ]: i a previous extraction step of the plant materials as well as a preliminary consequent purification step; ii fractionation of the mixture in order to isolate pure pigments and iii the final characterization and identification of pure anthocyanins compounds Table 3.
Strategies for preparation and characterization of anthocyanin samples from plant materials [ 38 ]. In order to avoid sample oxidation, thermal degradation, chemical and biochemical changes under mild extraction conditions [ ] are recommended and drying, lyophilized, or frozen samples should be used.
The deterioration processes of the compounds may be avoided by the addition of antioxidants compounds, by using inert atmospheres or working in the absence of light. However, no definitive procedure for storage and collection has been established. To determine either the target analytes in their various conjugated forms or the aglycones is an important question [ , ] to answer. When dealing with plant, food products and biological matrices, the instant conjugates are usually search, whereas in the other instances it is necessary to carry out a preliminary hydrolysis, e.
Intentional hydrolysis for obtaining the aglycones of some flavonoid or derivatization of some fatty acids to esters is sometimes intentionally incorporated [ 79 ] to the extraction process. Extraction represents an important phase [ 34 , 38 , 39 , 79 , ] in the isolation, identification and utilization of anthocyanins. Anthocyanins are usually recovered by mean of a solvent extraction procedure.
Parameters such as solvent-extraction kind and its composition, liquid-to-solid ratio, extraction time and temperature require [ ] proper optimization. The flavylium cation form of anthocyanins is red and stable in a highly acidic medium. Thus, the extraction solution should be enough slightly acid to maintain the flavylium cation form [ ], but not so much as to cause partial hydrolysis of the acyl moieties in acylated anthocyanins.
Protocols of extraction and analysis of plant materials and biological fluids are, however, difficult to accomplish because of [ ] the structural diversity of anthocyanins and their susceptibility to heat, pH, metal complexes and copigmentation. Flavonoid glycosides are of a more polar nature, whereas aglicones are extracted either with alcohols or alcohol-water mixtures.
Cold acidified solvents polar organic solvents, water under mild conditions [ , ] are used for the extraction of anthocyanins. The organic solvent usually used is methanol.
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However, solvents such as acetone, ethanol, or acetonitrile may be used. These solvents system denature the cell membranes [ 93 ] also dissolving and stabilizing the anthocyanins. When a mineral acid is used it may assist [ ] to the loss of the attached acyl group. Sulfurous water also allows [ ] the reduction of organic solvent and cost extraction. Phytochemical recovery of a good antioxidant from various sources may be achieved by using solvent extraction.
The conventional solvent extraction procedure suffers from the drawback of requiring subsequent extraction and cleanup prior analysis. In addition, health and safety risks are associated with the use of large amounts of organic solvents, being on the other hand environmentally unfriendly. A modern trend toward [ ]: 1 the use of samples smaller in size, volume, or organic solvent content; 2 an extraction with increasing selectivity or specificity; 3 improved recoveries and reproducibility; 4 greater automation facilities.
Bioactive Heterocycles Vi Flavonoids And Anthocyanins In Plants And Latest Bioactive Heterocycles I
Selected applications of sample preparation techniques on anthocyanin compounds are listed in Table 4 [ — ], an extension of applications previously published by the authors in [ 39 ]. The applications of other novel nonthermal techniques will be the subject of further study. Figure 6 shows a schematic representation of a highly separation and purification methodology based on a macroporus polymeric adsorbent for the determination of anthocyanins in bilberry [ ].
Source: Ampliation from Ref. Schematic representation of a highly separation and purification of anthocyanins from bilberry based on macroporus polymeric adsorbent . The identification of anthocyanins has a critical role in taxonomic [ ] and adulteration [ ] studies, besides anthocyanins might replay synthetic days. HPLC, especially in the reversed phase, is the most widely used separation technique. However, even at low pH [ 31 , 32 , 35 , ] some interconversion between the anthocyanin flavylium cationic and carbinol pseudobasic forms occurs. Spectroscopy is the main technique used due to its simplicity and low cost providing very useful qualitative and quantitative information anthocyanins have a specific and intense absorbance band in the range of — nm [ — ], however the difficulty in obtaining reference compounds and the spectral similarities of the anthocyanins represent important drawbacks.
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Various MS instruments, as well as the advances in nuclear magnetic resonance NMR have given a fresh impetus to anthocyanin analysis [ 78 , 83 , ]. NMR identification of anthocyanin compounds [ 78 ] offers new promising approaches for analysis of complex phenolic mixtures.
NMR is based primarily on the analysis of 1 H NMR spectra but important structural information can also be provided by 13 C NMR [ ] and, especially for compounds that have many quaternary carbons, by combining homo and heteronuclear 2D and 3D techniques. However, the relatively high capital costs are still an impediment [ ] to their routine use in enforcement laboratories, a fact that must be taken into consideration.
The almost universal distribution of anthocyanins in flowering plants makes them also suitable for chemotaxonomic considerations [ ] both at the family and genus level. Differential anthocyanins profiles may be used [ ] for the detection and adulteration in specific commodities of berry fruit products.
Bioactive Heterocycles Vi Flavonoids And Anthocyanins In Plants And Latest Bioactive Heterocycles I
In the last few years, special attention has been paid [ ] to the isolation and characterization of compounds that may delay the onset of aging, as occurs with some berry phenolics. The extremely low levels of anthocyanins usually present in biological samples [ 57 , , , ] blood plasma and body tissues possess further challenges to their identification and quantification, together with the lack of commercially available anthocyanin standards.
In last decades, polyphenol chemistry has experienced an explosion of knowledge, being anthocyanins one of the most widely studied groups [ 27 , , ], due to its great potential for practical applications in various fields, contributing in addition this to obtain a better understanding of the chemistry of life. Anthocyanins occur in all plant tissues including leaves, stems, roots, flowers and fruits imparting color. Anthocyanins are responsible for the red, purple and dark blue colors of many fruits and berries [ 68 , — ].
Anthocyanins have antioxidant activity [ 55 , , — ] preventing radical formation. These nontoxic natural pigments have received considerable attention from such as food, pharmaceutical and nutritional industries due to their potential applications in color-processed food and medicines [ 31 , 33 , , ] which may replace synthetic dyes.
It was only a few decades ago that anthocyanins were regarded as highly degradable compounds and the research studies mainly were focused on their chemical structures, color stability, use as food constituents and changes in foods during storage. Anthocyanins are now recognized as food constituents with potential health benefits [ , ] and research related to these properties has markedly progressed at the molecular level.
Anthocyanins will continue to attract researchers across various disciplines, including those involved in the creation of new flower varieties with novel colors. Research on the health benefits of anthocyanins will provide information [ ] on underlying molecular mechanisms and absorption and metabolism. Moreover, once these benefits are proven in humans, development of foods and dietary supplements in a capsule form [ , , ] can be accelerated to promote the proven functions, i.
The development of analytical techniques to determine the identity and quantities of anthocyanins in natural products, as well as their effects in vivo and in vitro , is challenging.
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Solvent extraction involving the use of acidic solvents has been the most commonly used method [ 36 , 79 ] for the recovery of diverse compounds found in flavonoids, including anthocyanins. The traditional solid-liquid or liquid-liquid extraction offers good recovery. Nevertheless, they are often described as laborious, time and solvent consuming and prone to errors. However, in recent years there are trends toward other environmentally and economically friendlier extraction techniques [ 38 , 39 , , , , , ] using a smaller amount of nontoxic solvents and sample sizes, reducing working time and increasing selectivity, specificity, recovery and potential of automation.
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Downloaded: Abstract Anthocyanins are naturally occuring pigments belonging to the group of flavonoids, a subclass of the polyphenol family. Keywords anthocyanins pigments sample preparation extraction.
Introduction The progress in the last years in the interdisciplinary fields of chemistry, separation science, biology and pharmacy has boosted the natural product chemistry research [ 1 — 4 ], providing a valuable information about many classes of naturally occurring dietary phytochemicals. Polyphenols Plant phenols are among the most abundant and widely represented class of existing plant natural products [ 40 ] thanks to the continuous evolution of new genes brought about by gene duplication and mutation and subsequent recruitment and adaptation to specific functions.
Anthocyanins Anthocyanins are the largest group of phenolic pigments and the most important group of water-soluble pigments in plants [ 68 , 69 , — ], responsible for the red, purple and blue colors found in many fruits, vegetables, cereal grains and flowers, being odorless and nearly flavorless and contributing to taste as a moderately astringent sensation.
Chemical structure Chemically, anthocyanins are glycosylated polyhydroxy or polymethoxy derivatives of 2-phenylbenzopyrilium [ 68 , , ], usually with molecular weights ranging from to medium-size biomolecules and containing two benzyl rings A and B. Anthocyanidin Abbrev. Source: Ref. Antioxidant activity The relationship between diet and health has been known since ancient times and recent studies demonstrated the relevance of many food components in modulating health [ 1 ]. Color Anthocyanins are the pigment compounds responsible for pale yellow, orange, red, magenta, violet and blue colors [ ].
Copigmentation Copigmentation is almost always a variation toward blueness. Intake Anthocyanins are widely ingested by humans, mainly due to consumption [ ] of red fruits like berries and red grapes , vegetables such as red cabbage, red wines, cereals and purple corn. Pickup not available. About This Item We aim to show you accurate product information.