Oenin and Quercetin Copigmentation: Highlights From Density Functional Theory

Intermolecular interactions between malvidin-3-O-glucoside and caffeic acid: Structural and thermodynamic characterization and its effect on real wine color quality

The copigmentation effect between malvidin-3-O-glucoside and caffeic acid was comprehensive inquiry on the model wine solution, theoretical simulation and real wine. Thermodynamic parameters were determined by UV/Visible spectroscopy and Isothermal titration calorimetry (ITC). Theoretical data were obtained employing a dispersion-corrected density functional approach. The effects in real wines were investigated by adding the caffeic acid during different fermentation periods. Results shown that the copigmentation reaction between caffeic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersions forces. Computations show that the polyhydroxyl sugar moiety and phenolic hydroxyl groups are the key active sites. The addition of caffeic acid in post-alcohol fermentation samples evidences an improving color characteristics in the wine.

Gallic acid improves color quality and stability of red wine via physico-chemical interaction and chemical transformation as revealed by thermodynamics, real wine dynamics and benchmark quantum mechanical calculations

The aim of this study was to explore the copigmentation effect of gallic acid on red wine color and to dissect its mechanism at the molecular level. Three-dimensional studies, e.g., in model wine, in real wine and in silico, and multiple indicators, e.g., color, spectrum, thermodynamics and phenolic dynamics, were employed. The results showed that gallic acid significantly enhanced the color quality and stability of red wine. Physico-chemical interactions and chemical transformations should be the most likely mechanism, and physico-chemical interactions are also a prerequisite for chemical transformations. QM calculations of the physico-chemical interactions proved that the binding between gallic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersion forces. The sugar moiety of malvidin-3-O-glucoside and the phenolic hydroxyl groups of gallic acid affect the formation of hydrogen bonds, while the dispersion interaction was related to the stacking of the molecular skeleton.

Advancements in the promotion of pyranoanthocyanins formation in wine: A review of current research

Pyranoanthocyanin (PACN) is a class of anthocyanin (ACN)-derived pigments found in aged red wines, which has certain advantages over the prototype ACN in terms of stability, and biological activity. However, the efficiency and yield of PACNs in the natural fermentation system are low. This article summarizes five frequently employed physical processing techniques that can accelerate the formation of PACN. From a mechanistic standpoint, these techniques can produce large amounts of active substances, further promoting the extracellular release of phenolics and the formation of some cofactors and PACNs' pyran rings. Precursor substances and environmental factors affecting PACN yields are also pointed out. It mainly included the parent ring substitution in ACNs, the type and quantity of glycosides, the electron donating ability and concentration of cofactors, etc. Thus, this article aims to provide an overview of the advancements in processing techniques, thereby facilitating their wider utilization in the food and beverage industry.

Supramolecular Study of the Interactions between Malvidin-3-O-Glucoside and Wine Phenolic Compounds: Influence on Color

Supramolecular study of the interactions between the major wine anthocyanin, malvidin-3-O-glucoside (Mv3G) and different wine phenolic compounds (quercetin 3-O-β-glucopyranoside (QG), caffeic acid, (-)-epicatechin, (+)-catechin, and gallic acid) has been performed at two different molar ratios (1:1 and 1:2) in acidic medium where flavylium cation predominates (pH ≤ 2). Color variations have been evaluated by differential colorimetry using CIELAB color space. These studies have been complemented with isothermal titration calorimetry assays and molecular dynamics simulations. The color of Mv3G flavylium cation is modified by the interaction with QG toward more bluish and intense colors. Interaction constants between the anthocyanin and the different phenolic compounds were obtained, ranging from 9.72 × 108 M-1 for QG to 1.50 × 102 M-1 for catechin. Hydrophobic interactions and H-bonds are the main driving forces in the pigment/copigment aggregation, except for the interactions where caffeic acid is involved, in which hydrophobic interactions acquire greater preponderance.

Investigating the Role of Odorant-Polymer Interactions in the Aroma Perception of Red Wine: A Density Functional Theory-Based Approach

The aroma of red wine results from the intricate interplay between aroma compounds (odorants) and complex polymers generated during fermentation. This study combines density functional theory (DFT), human sensory experiments, and nuclear magnetic resonance to investigate the impact of odorant-polymer interactions on wine aroma. Molecular aggregation patterns of odorants with polymer segments are identified, indicating the crucial role of intermolecular noncovalent interactions, such as hydrogen bonds and van der Waals interactions, in stabilizing odorant-polymer conformations. Certain odorants, including 3-isobutyl-2-methoxypyrazine and cis-whisky lactone, exhibit high binding affinity to specific polymer segments, such as (+)-catechin and p-coumaric acid, resulting in substantial changes in the perceived aroma. Their strong binding affinities correlate with changes in sensory experiments for binary mixtures. The results provide insights into the molecular mechanisms of odorant-polymer interactions in red wine with the potential of DFT calculations as a tool for predicting and tailoring red wine aroma.

A comparative metabolomics investigation of flavonoid variation in faba bean flowers

INTRODUCTION

Faba bean (Vicia faba L.) flowers are edible and used as garnishes because of their aroma, sweet flavor and attractive colors. Anthocyanins are the common plant pigments that give flowers their vivid colors, whereas non-anthocyanin flavonoids can serve as co-pigments that can modify the color intensity of flowers.

OBJECTIVES

To explore the polyphenol diversity and differences in standard and wing petals of faba bean flowers; and identify glycosylated flavonoids that contribute to flower color.

METHODS

Flower standard and wing petals from 30 faba bean genotypes (eight color groups with a total of 60 samples) were used for polyphenol extraction. Samples were analyzed using a targeted method and a semi-untargeted analysis using liquid chromatography-high resolution mass spectrometry (LC-HRMS) combined with photodiode array (PDA) detection. Compound Discoverer software was used for polyphenol identification and multivariate analysis.

RESULTS

The semi-untargeted analysis guided by the PDA detected 90 flavonoid metabolites present in faba bean flower petals. Ten anthocyanins largely influenced the flower colors, but other flavonoids (63 flavonols and 12 flavones) found with variable levels in different flower color groups appeared to also influence color, especially in mixed colors.

CONCLUSION

Analysis of the different colored faba bean flowers confirmed that the color variation between the flowers was mainly controlled by anthocyanins in brown, red and purple-red flowers. Of the other flavonoids, multiglycosylated kaempferols were abundant in white and brown flowers, monoglycosylated kaempferols were common in red and purple-red flowers, and quercetin and apigenin glycosides were abundant co-pigments in purple-red flowers.

Visual Representation of Red Wine Color: Methodology, Comparison and Applications

A visual and easy-to-implement representation approach of red wine color is proposed in this work. The wine color under standard conditions, called feature color, was reproduced in the form of a circular spot. The feature color was further decomposed into two orthogonal aspects, the chromatic and light-dark components, characterized in the form of chromaticity distribution plane and lightness distribution plane, respectively. The color characterization of wine samples showed that this method well represented the color characteristics and can provide intuitive visual perception of wine color, in a way that is more reliable and convenient than the photographic method. The applications for monitoring the color evolution during winery and laboratory fermentation and the age discrimination of 175 commercial red wines suggest that this visual method is effective for color management and control of wine during fermentation and aging. The proposed method is a convenient way to present, store, convey, understand, analyze and compare the color information of wines.

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.

Natural Blues: Structure Meets Function in Anthocyanins

Choices of blue food colourants are extremely limited, with only two options in the USA, synthetic blue no. 1 and no. 2, and a third available in Europe, patent blue V. The food industry is investing heavily in finding naturally derived replacements, with limited success to date. Here, we review the complex and multifold mechanisms whereby blue pigmentation by anthocyanins is achieved in nature. Our aim is to explain how structure determines the functionality of anthocyanin pigments, particularly their colour and their stability. Where possible, we describe the impact of progressive decorations on colour and stability, drawn from extensive but diverse physico-chemical studies. We also consider briefly how this understanding could be harnessed to develop blue food colourants on the basis of the understanding of how anthocyanins create blues in nature.

Phenolic matrix effect on aroma formation of terpenes during simulated wine fermentation - Part I: Phenolic acids

In this study, fermentations were performed using simulated grape juice supplemented with terpene glycosides (TGs), extracted from Vitis vinifera L. Meili, and phenolic acids (gallic acid or p-coumaric acid). Free terpenes were detected using solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) every day during the fermentation, and the aromas of final wines were evaluated by panelists. Quantum mechanical (QM) calculations performed at density functional level of theory were used to uncover the structural and thermodynamic properties of the binding between phenolic acids and free terpenes (or TGs). Results showed that phenolic acids remarkably inhibited TG hydrolysis and free terpene volatilization, and affected wine aroma perception. QM calculations revealed that phenolic acids can bind to linalool and its glycoside spontaneously (ΔG < 0) via hydrogen bonding and dispersive forces. These findings indicate that the matrix effect of phenolic acids can effectively control the release and modulate the global feature of wine aromas.

Polyphenols: Natural Antioxidants to Be Used as a Quality Tool in Wine Authenticity

Polyphenols are a diverse group of compounds possessing various health-promoting properties that are of utmost importance for many wine sensory attributes. Apart from genetic and environmental parameters, the implementation of specific oenological practices as well as the subsequent storage conditions deeply affect the content and nature of the polyphenols present in wine. However, polyphenols are effectively employed in authenticity studies. Provision of authentic wines to the market has always been a prerequisite meaning that the declarations on the wine label should mirror the composition and provenance of this intriguing product. Nonetheless, multiple cases of intentional or unintentional wine mislabeling have been recorded alarming wine consumers who demand for strict controls safeguarding wine authenticity. The emergence of novel platforms employing instrumentation of exceptional selectivity and sensitivity along with the use of advanced chemometrics such as NMR (nuclear magnetic resonance)- and MS (mass spectrometry)-based metabolomics is considered as a powerful asset towards wine authentication.

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.

Tuning Optical Properties of Chalcone Derivatives: A Computational Study

The conformational feature of noncovalent complexes of two borondifluoride chalcone derivatives was assessed using DFT-D2. The corresponding optical properties were analyzed based on time-dependent density functional theory calculations. As already described in such complexes, the π-stacking interaction existing between both fragments allowed formation of a new absorption band corresponding to the S0 → S1 transition. However, this band appears very close to the most intense band corresponding the S0 → S2 transition.

Antioxidant properties and free radical scavenging mechanisms of cyclocurcumin

Cyclocurcumin has a strong ability to scavenge ˙OH by its 4′-OH phenolic hydroxyl via a hydrogen-atom transfer mechanism in a physiological environment.