Copigmentation Complexes Research Articles

Black chokeberry (Aronia melanocarpa) copigmentation reaction: Thermodynamic and kinetic investigations

Two type of parameters (thermodynamics and kinetics) were used to determine thermal stability of copigmentation process in black chokeberry: chlorogenic acid system. According to thermodynamic investigations copigmentation complex was destroyed at high temperature and restored again at low temperature. Different parameters kinetic rate constant, energy of activation and z-factor were presented and the reaction Based on them the order of the reaction was determined as first order.

Solubility of Quercetin in Wines

Quercetin solubility at 18 °C and 0 °C was determined in an hydroalcoholic buffer solution with pH 3.20 and in four Italian wines to study the formation of quercetin precipitate mechanism in wines. The wines selected were Barbera 2018 for the typically high content in bisulfite bleachable pigments, red Cirò 2014, for its typically high content of flavonoids, Sangiovese 2014, for the presence of quercetin deposits in bottle, and white Cirò 2018, for the absence of red pigments. All the samples were spiked with 30 mg/L quercetin. The amount of quercetin solubilized at 18 °C and 0 °C in the hydroalcoholic buffer was much lower than in wines, while that solubilised in Barbera was much higher compared to red Cirò, Sangiovese and white Cirò. Solubilised quercetin was lower in all wine samples stored at 0 °C than in those at 18 °C. The pigment composition of the three red wines examined suggested that the over-solubility of quercetin could be due to the formation of soluble co-pigmentation complexes between quercetin and monomer anthocyanins and/or bisulphate-bleachable flavanol-anthocyanin pigments. A positive correlation between quercetin solubility and bleachable pigment was noted: the richer the wine in bleachable pigments, the higher the solubility of quercetin. Quercetin haze formation appeared due to the release of quercetin from co-pigmentation complexes during wine maturation and storage ,as its counterpart, anthocyanins, form non-bleachable pigments or are degraded in hydrolytic or oxidation reactions. Quercetin in aged red wines seemed to reach a content similar to that of white wine spiked with quercetin. Nevertheless, the quercetin content of aged red wines in which a quercetin haze has been found could be lower than that when added white wine, due to its degradation probably being induced by oxidation reactions. Finally, the solubilized quercetin content in white Cirò, which was higher than the hydroalcoholic buffer solution, suggested that there may be different substances in wines than pigments that prevent the growth of quercetin crystals. However, their nature was not determined in this study.

Copigmentation and stabilization of anthocyanins using organic molecules and encapsulation techniques

Natural colorants/pigments such as anthocyanins, carotenoids, betalains, and chlorophylls have been generally used in the food industry as coloring agents. However, there are challenges related to color fading during food processing, storage, and commercialization due to the low stability of natural colorants compared to synthetic ones. Among them, anthocyanins are potential food colorants due to their color, low toxicity, and biological properties. However, the low chemical and thermal stability of anthocyanins have limited their use on a commercial scale. Copigmentation is the most commonly used technique for anthocyanin stabilization. This technique provides many advantages associated with the stability of anthocyanins. Natural anthocyanin pigments and copigments (e.g. polymers, phenolic compounds, and carbohydrates) form non-covalent complexes, which stabilize and modulate colors in a wide range of plants, fruits, and food products derived from them (including wines, jams, purees, and syrups). Over the past decade, research studies have been conducted to understand the molecular structure of copigment and the mechanism of copigmentation. This review summarizes this phenomenon to provide a comprehensive description of the interactions between anthocyanin and copigment (the dispersion and electrostatic components of π − π stacking, the hydrophobic effect, and hydrogen-bonding) occurring in copigmentation complexes. The trend of integrating copigmentation and encapsulation has been recently started to develop. In this paper, we also attempt to provide a comprehensive view of the effective approaches including spray and freeze-drying, emulsification, gelation, and their combinations for encapsulating copigmented anthocyanins.

Acetylation of Malvidin-3-O-glucoside Impedes Intermolecular Copigmentation: Experimental and Theoretical Investigations.

Malvidin-3-O-(6-O-acetyl)-glucoside is usually the most abundant acylated anthocyanin in red wines. In this work, intermolecular copigmentation of malvidin-3-O-(6-O-acetyl)-glucoside and malvidin-3-O-glucoside with three phenolic copigments was carried out in model wine solutions, and the influence of the acetylation group was evaluated emphatically using experimental and theoretical approaches. This study found that there was no distinct coloring difference in the two anthocyanins themselves; however, the hyperchromic effects were smaller in malvidin-3-O-(6-O-acetyl)-glucoside solutions with the existence of insufficient copigments. Thermodynamic analysis confirmed that malvidin-3-O-(6-O-acetyl)-glucoside showed weaker affinity (smaller K values) toward the three copigments compared with its non-acylated form. Theoretical analysis also indicated that the existence of the acetylation group changed the spatial conformations and non-covalent interactions (hydrogen bonds and van der Waals forces) of the copigmentation complexes, which might be due to the potential steric hindrance effect. In conclusion, the results revealed that the acetylation group on anthocyanin glycosyl could impede intermolecular copigmentation.

Intermolecular copigmentation between five common 3-O-monoglucosidic anthocyanins and three phenolics in red wine model solutions: The influence of substituent pattern of anthocyanin B ring

In this study, intermolecular copigmentation between five primary wine monoglucosidic anthocyanins (cyanidin-3-O-glucoside, peonidin-3-O-glucoside, delphinidin-3-O-glucoside, petunidin-3-O-glucoside, and malvidin-3-O-glucoside) and three common wine phenolics (gallic acid, (−)-epicatechin, and quercetin-3-O-glucoside) were investigated through experimental and theoretical methods, and the influence of substituent pattern of anthocyanin B ring was studied emphatically. Chromatic and thermodynamic analysis showed there were great differences among these different pigment-copigment systems. Spatial conformations of the 15 copigmentation complexes were obtained through theoretical calculation, and diverse π-π stacking modes were observed. These results indicated that the substituent pattern of anthocyanin B ring had significant impact on its affinity to copigments, and more, the structures of pigments and copigments determined the color expression and stability of copigmentation together.

Oenin/Syringic Acid Copigmentation: Insights From a Theoretical Study.

On the basis of the dispersion-corrected density functional theory, a computational model is proposed to describe the oenin/syringic acid copigmentation and to explore the non-covalent interaction between the anthocyanin and the copigment in the framework of implicit solvent approach. The predicted binding free energy and visible spectrum shift of this copigmentation complex are in accordance with the experimental observations. The used model provides a good structural description of oenin/syringic acid complex and suggests that the intermolecular hydrogen bonding, in which the hydroxyl-rich sugar moiety in oenin plays a key role, may be the determinant for the formation and nature of the copigmentation complex.

Oenin and Quercetin Copigmentation: Highlights From Density Functional Theory.

Making use of anthocyanin copigmentation, it is possible to effectively improve color quality and stability of red wines and other foods. This can be done by selecting strong copigments, but a 1-fold experimental screening usually entails a high cost and a low efficiency. The aim of this work is to show how a theoretical model based on density functional theory can be useful for an accurate and rapid prediction of copigmentation ability of a copigment. The present study, concerning the copigmentation between oenin and quercetin under the framework of implicit solvent, indicates that, in these conditions, the intermolecular hydrogen bonds play an important role in the system stabilization. The dispersion interaction slightly affects the structure, energies and UV-Vis spectral properties of the copigmentation complex.

Quantum Chemical Investigation of the Intramolecular Copigmentation Complex of an Acylated Anthocyanin

Anthocyanins are the natural plant pigments responsible for most of the red, blue and purple colors of flowers and fruit. One method of stabilization of the color of anthocyanins in nature is intramolecular copigmentation, in which a copigment molecule covalently attached to one of the sugar residues complexes with the anthocyanin cation chromophore. In the present work, two quantum chemical methodologies, time-dependent density functional theory (TD-DFT) and second.order algebraic diagrammatic construction (ADC(2)), were employed to predict the absorption spectra in vacuum and conductor-like screening model (COSMO) water of a natural anthocyanin containing an ester of coumaric acid (copigment) bound to the sugar residue of a cyanidin chromophore. ADC(2) in water adequately reproduces the experimental spectra with and without intramolecular copigmentation, pointing to this theoretical technique as a promising approach for predicting the spectroscopic properties of natural (and nature-inspired) dyes and pigments.

Anthocyanin pigment stability of Cornus mas-Macrocarpa under treatment with pH and some organic acids.

The use of colors in food industry is essential for the creation of new products or their improvement. As an important pigment group, anthocyanin could be used as a natural coloring pigment in foods. This study aims at exploring strategies that result in color stability of anthocyanin in pear‐shaped variety of blueberry (Cornus mas–Macrocarpa). In this study, the effects of different pH values (1, 2, 3, 4) as well as various concentrations (0, 120, 240, 480, 960 mg/L) of five copigments, including tannic, caffeic, benzoic, and coumaric acids, on anthocyanin copigment complexes (ratio 1:1) were investigated. The studied copigments were tannic, caffeic, benzoic, and coumaric acids. Anthocyanin was influenced by the highest concentration of 960 mg/L copigment in the presence of different pHs. Five groups were considered, one of which contained anthocyanin without copigment and the rest consisted of copigments. To evaluate the response of copigmentation through spectrophotometer, absorbance from samples was measured after 30 min of adding copigment to anthocyanin in the range of 450–600 nm wavelengths. The results showed that caffeic acid possessed the greatest anthocyanin stability compared to other copigments and it was the best copigment. An increase in the concentrations of copigments led to a higher level of anthocyanin stability and changes in hyperchromic and bathochromic. Moreover, the results revealed that the strongest hyperchromic effect for all organic acids was observed in pH 2, and the strongest bathochromic changes were observed in pH 4.

Colorimetric study of malvidin-3-O-glucoside copigmented by phenolic compounds: The effect of molar ratio, temperature, pH, and ethanol content on color expression of red wine model solutions

In the recent research, the copigmentations of malvidin-3-O-glucoside with eight types of phenolic copigments have been investigated. The influence of the pigment/copigment molar ratio, the reaction temperature, the pH and the ethanol content of solutions has been examined. The results showed that the copigmentation effect was dependent on not only the particular structures of the phenolic compounds but also the factors of the reaction systems. The increase of the copigment concentration can strengthen the copigmentation effect, improve the solution color, and enhance the red-purple features. Different temperatures had different influences on the copigmentation reactions. The destruction of the copigmentation complexes can result in the hypsochromic shift of the reaction solution when the temperature was higher than 20°C. The bathochromic shift of the solution gradually progressed with the increase of the pH value. A significant copigmentation feature was spotted when pH reached 3.0, which demonstrates obvious red-purple characterization. The addition of the ethanol weakened the copigmentation effect. According to measurement through color analysis, it was found that the color differences caused by ethanol in red wine were typically attributed to quantitative changes. Remarkably, all of the above delicate color deviations caused by the structural or environmental factors can be precisely and conveniently depicted via the CIELAB space analysis.

Effect of chlorogenic acid on spectral properties and stability of acylated and non-acylated cyanidin-3-O-glycosides

Spectral characteristics and heat stability (90°C, 5h) of six isolated, structurally related cyanidin-3-O-glycosides from black carrot were investigated in aqueous solutions (pH 3.6 and 4.6) supplemented with chlorogenic acid (molar anthocyanin:co-pigment ratios 1:62.5–1:250). Chlorogenic acid supplementation generally increased absorbance of non-acylated anthocyanins by up to 97.9 and 122.9% at pH 3.6 and 4.6, respectively, being mainly attributed to the formation of intermolecular anthocyanin:co-pigment complexes. The effect significantly decreased when the chain length of the 3-O-linked non-acylated anthocyanins was increased from mono- to di- to triglycosyl moieties, possibly due to steric interferences of bound sugars and co-pigments. Intermolecular co-pigmentation was investigated for the first time for feruloylated and sinapoylated cyanidin-3-O-triglycosides. They exhibited weaker effects (10.8–16.0%) at pH 4.6, and no spectral response was observed at pH 3.6. Chlorogenic acid addition evoked weak enhancement of thermal pigment stability at pH 3.6, while it was highly detrimental for all anthocyanins at pH 4.6.

Stability of blueberry (Cornus mas – Yulyush) anthocyanin pigment under pH and co-pigment treatments

ABSTRACTIn this study, the effects of different pH values and co-pigments, including tannic, caffeic, benzoic, and coumaric acids, in various concentrations on anthocyanin co-pigment complexes (ratio 1:1) were investigated. The anthocyanin was extracted from a round sweet variety of blueberry and subjected to the highest co-pigment concentration (960 mg/l) at different pH values. The results showed that caffeic acid produced the highest stability of anthocyanin compared to the other co-pigments. In addition, benzoic acid had the lowest hyperchromic and bathochromic changes. A positive correlation was found between the co-pigment concentrations and the stability of anthocyanin as well as hyperchromic and bathochromic changes. The results also demonstrated that higher pH values resulted in further destruction of anthocyanin. Furthermore, the absorption rate of anthocyanin in the anthocyanin–co-pigment complex within lower pH values was more compared with the higher ones. The strongest hyperchromic and bathochromic effects for all organic acids were observed in pH values 1 and 4, respectively. It can be concluded that among the tested co-pigments, caffeic acid was the best co-pigment, while benzoic acid was the weakest, which was not suitable for anthocyanin in the round sweet variety of blueberry.

Stabilizing and Modulating Color by Copigmentation: Insights from Theory and Experiment.

Natural anthocyanin pigments/dyes and phenolic copigments/co-dyes form noncovalent complexes, which stabilize and modulate (in particular blue, violet, and red) colors in flowers, berries, and food products derived from them (including wines, jams, purees, and syrups). This noncovalent association and their electronic and optical implications constitute the copigmentation phenomenon. Over the past decade, experimental and theoretical studies have enabled a molecular understanding of copigmentation. This review revisits this phenomenon to provide a comprehensive description of the nature of binding (the dispersion and electrostatic components of π-π stacking, the hydrophobic effect, and possible hydrogen-bonding between pigment and copigment) and of spectral modifications occurring in copigmentation complexes, in which charge transfer plays an important role. Particular attention is paid to applications of copigmentation in food chemistry.

The color expression of copigmentation between malvidin-3-O-glucoside and three phenolic aldehydes in model solutions: The effects of pH and molar ratio

Copigmentation was investigated in model solutions between the anthocyanin malvidin-3-O-glucoside and three phenolic aldehydes (vanillic, syringic and coniferyl aldehydes) as a function of the pH and the pigment/copigment molar ratio. Tristimulus colorimetry was applied to evaluate the chromatic variations induced by copigmentation process. The results indicated that the greatest magnitude of copigmentation was obtained at pH 3.0 and molar ratio of 1:100, being significantly higher with coniferyl aldehyde, followed by syringic and vanillic aldehydes. The equilibrium constant (K) and Gibbs free energies (ΔG°) determined here show a spontaneous exothermic reaction. Theoretical calculations (ΔGbinding, ΔE) specified the relative arrangement of the pigment and copigment molecules within the complexes. In addition, an atoms in molecules (AIM) analysis was used to explore the main driving forces contributing to the formation of copigmentation complexes.

Copigmentation between malvidin-3-O-glucoside and hydroxycinnamic acids in red wine model solutions: Investigations with experimental and theoretical methods

The copigmentation effect between malvidin-3-O-glucoside and three hydroxycinnamic acids (p-coumaric, caffeic and ferulic acids) on the color expression was assessed in red wine model solutions. The colorimetric parameters indicated that the increasing concentration of these copigments could enhance the color intensity of the wine-like solutions (hyperchromic effect and bathochromic shift), and displayed the darker and more vivid bluish chromatic properties. The equilibrium constant (K), stoichiometric ratio (n) and thermodynamic parameters (∆G°, ∆H°, ∆S°) were determined by the spectrophotometric methods, showing the generally spontaneous exothermic character of the process. In addition, quantum chemical investigations were performed to interpret the absorption differences. The results showed that the ferulic acid was the more powerful copigment compared with the other two hydroxycinnamic counterparts, indicating that the copigmentation was not only correlated to the concentration of the copigments but also strongly dependent on their molecular structures. AIM analysis was also used to explore the driving forces contributing to the copigmentation, which suggested that the hydrogen bond and van der Waals interactions were the main driving forces for the three pigment–copigment complexes.

Copigmentation of malvidin-3-O-glucoside with five hydroxybenzoic acids in red wine model solutions: Experimental and theoretical investigations

In the present research, the copigmentations of malvidin-3-O-glucoside with five hydroxybenzoic cofactors (p-hydroxybenzoic acid, protocatechuic acid, gallic acid, vanillic acid, and syringic acid) were investigated. The influence of the concentration of these cofactors and the reaction temperature was examined. The equilibrium constant (K), stoichiometric ratio (n) and the thermodynamic parameters (ΔG°, ΔH°, ΔS°) related to the copigmentation were also reported here. Theoretical calculations were performed to identify the relative arrangement between the pigment and cofactors in the copigmentation complexes. Besides, the comparison of the relative binding free energies (ΔΔGbinding) derived from the theoretical calculations and experimental data were made, and the binding strength of these copigmentation complexes was discussed with the interaction energies (ΔE). AIM analysis was also used to explore the main driving forces contributing to the copigmentation. In the comparison of the five studied cofactors, syringic acid had a stronger copigmentation effect than the other four phenolic acids investigated.

The Effects Catechin on Stability of Grape Anthocyanin – Copigment Complex

The color of anthocyanins is unstable and quickly decolourized by reactions. Thus anthocyanins in living cells may have mechanisms for resistance to maintain color stability. Copigmentation is the main color – stabilizing mechanism. In this study copigmentation of anthocyanin in Seedless Red grape were investigated with catechin copigment. The dependence of the copigmentation process on the heating, UV and copigment concentration was studied. Five levels of copigment concentrations as: 0, 120, 240, 480, 960 (mg/l) were examined. The copigmentation effects increased with copigment contain. During UV irradiation, anthocyanin-copigmentation complex showed higher stability in comparison with anthocyanins. Also UV irradiation has the biggest effect on the copigmentation complex in comparision with heating. Keyword: Anthocyanin, Catechin, Copigment, Heating, Seedless Red

Structural Features of Copigmentation of Oenin with Different Polyphenol Copigments

The copigmentation binding constants (K) for the interaction of different copigments with oenin (major red wine anthocyanin) were determined. All tests were performed in a 12% ethanol citrate buffer solution (0.2 M) at pH 3.5, with an ionic strength adjusted to 0.5 M by the addition of sodium chloride. Over the past years, several copigmentation studies were made and many copigments were tested, but none of them included prodelphinidin B3 or a dimeric-type adduct like oenin-(O)-catechin, probably due to the difficulty in obtaining them. The data yielded from this study allowed concluding that (a) the presence of a pyrogallol group in the B ring of the flavan-3-ol structure slightly increases the copimentation potential and (b) within all copigments tested oenin-(O)-catechin was revealed to be the best. According to computational studies performed on epicatechin/oenin, epigallocatechin/oenin, procyanidin B3/oenin, and oenin-(O)-catechin/oenin complexes, the ΔGbinding energy of the oenin-(O)-catechin/oenin complex is the most negative compared to the other copigmentation complexes, hence being more stable and thermodynamically favored. All structural data show that oenin-(O)-catechin and epigallocatechin are closer to the pigment molecule, which is in accordance with these two copigments having the highest experimental copigmentation binding constants for oenin.

Photoprotection and the Photophysics of Acylated Anthocyanins

The proposed role of anthocyanins in protecting plants against excess solar radiation is consistent with the occurrence of ultrafast (5-25 ps) excited-state proton transfer as the major de-excitation pathway of these molecules. However, because natural anthocyanins absorb mainly in the visible region of the spectra, with only a narrow absorption band in the UV-B region, this highly efficient deactivation mechanism would essentially only protect the plant from visible light. On the other hand, ground-state charge-transfer complexes of anthocyanins with naturally occurring electron-donor co-pigments, such as hydroxylated flavones, flavonoids, and hydroxycinnamic or benzoic acids, do exhibit high UV-B absorptivities that complement that of the anthocyanins. In this work, we report a comparative study of the photophysics of the naturally occurring anthocyanin cyanin, intermolecular cyanin-coumaric acid complexes, and an acylated anthocyanin, that is, cyanin with a pendant coumaric ester co-pigment. Both inter- and intramolecular anthocyanin-co-pigment complexes are shown to have ultrafast energy dissipation pathways comparable to those of model flavylium cation-co-pigment complexes. However, from the standpoint of photoprotection, the results indicate that the covalent attachment of co-pigment molecules to the anthocyanin represents a much more efficient strategy by providing the plant with significant UV-B absorption capacity and at the same time coupling this absorption to efficient energy dissipation pathways (ultrafast internal conversion of the complexed form and fast energy transfer from the excited co-pigment to the anthocyanin followed by adiabatic proton transfer) that avoid net photochemical damage.

Influence of Copigment Derived from Tasmannia Pepper Leaf on Davidson's Plum Anthocyanins

Davidson's plum (Davidsonia pruriens, F. Muell.), a native to Australian rainforests, large, crimson-red fruit, which superficially resembles plum, has been commercially cultivated in Australia since 1990s. The current production volume exceeds market demands therefore this study was designed to evaluate the suitability of Davidson's plum extract as a source of anthocyanin-based food colorant. The stability of the Davidson's plum extract towards heat treatment at 95 °C was higher than that of commercial mulberry colorant, but inferior to colorants derived from red cabbage and purple sweetpotato. An addition of a variety of phenolic acids significantly increased color intensity indicating the formation of copigmentation complexes. Commercial chlorogenic acid as well as extract from a native Australian herb rich in chlorogenic acid, Tasmannia pepper leaf (Tasmannia lanceolata, R. Br.), were both tested in model soft drink solutions subjected to light irradiation and heat treatment. In both cases, the addition of the copigment resulted in a lasting increase in color intensity. In conclusion, Davidson's plum extract can successfully be utilized as a source of natural food color. Extract from Tasmania pepper leaf can be used as a co-pigment for Davidson's plum anthocyanins. The color properties of an anthocyanin colorant derived from the native Australian fruit Davidson's plum are comparable to those of mulberry, which is currently applied as a food colorant in Australian food products. Utilization of Davidson's plum fruit as a source of natural color will allow the industry to increase the range of natural pigments and will create new opportunities for the emerging native food industry.