Molecular binding between anthocyanins and pectic polysaccharides – Unveiling the role of pectic polysaccharides structure

Effect of dietary fiber addition on the content and in vitro bioaccessibility of antioxidants in red raspberry puree

The aim of the present study was to understand how the addition of pectin (2.5% and 5%) affected the content and bioaccessibility of phenolics in red raspberry puree. The results showed that the concentration of antioxidants in red raspberry puree was reduced with the addition of pectin. Similarly, addition of pectin to red raspberry puree significantly reduced the total phenolic content (15-20%), total antioxidant capacity (18-70%), and total monomeric anthocyanin (25-30%) after in vitro digestion. On the other hand, significant decreases in the bioaccessible amount of cyanidin (41%), cyanidin-3-glucoside (14%), cyanidin-3-rutinoside (17%), pelargonidin 3-glucoside (16%), and peonidin (28%) were observed after the addition of pectin (5% (w/w)) compared to the control (p < 0.05) as analyzed with the HPLC method. According to the LC-MS/MS analysis of red raspberry samples, five flavonoids (rutin, quercetin, kaempferol, myricetin, and phlorizin) and six phenolic acids (gallic acid, caffeic acid, chlorogenic acid, sinapic acid, p-coumaric acid, and ferulic acid) were detected. The effect of in vitro gastrointestinal digestion varied depending on the type of the phenolic compounds. Sinapic acid and phlorizin were not detected at all in the intestinal phase, indicating that they were completely degraded during digestion. The percentage bioaccessibility of gallic acid (49-88%), rutin (6-16%), and quercetin (23-33%) was decreased proportionally with the increase in the pectin content in red raspberry purees (p < 0.05). On the other hand, only 5% pectin addition to red raspberry puree resulted with a significant decrease in the amount of bioaccessible caffeic acid (8% to 5%), kaempferol (24% to 13%), ferulic acid (26% to 10%), and myricetin (91% to 57%) (p < 0.05). Overall, the present study highlighted that incorporation of pectin to red raspberry puree reduced the amount of bioaccessible polyphenols.

Natural and Synthetic Flavylium-Based Dyes: The Chemistry Behind the Color

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.

Recent advances in interactions between polyphenols and plant cell wall polysaccharides as studied using an adsorption technique

Polyphenols include flavonoids, phenolic acids, tannins and lignans which are known to have antioxidant, UV protection and antimicrobial properties. Among them the most commonly investigated are flavonoids and phenolic acids, which, due to their plant origin, may interact with the plant cell wall (PCW) components, specifically with its polysaccharides. Knowledge concerning the nature of the interactions between these components may be used in the production of functional food or in the development of food packaging materials with additional properties. The content of polyphenols in such products is responsible for their colour and taste, and may also act as a natural preservative. On the other hand, the PCW components may have protective role of polyphenols which has impact on their release in the human digestive system. Therefore, this review is an attempt to summarize the current state of knowledge that emerged after 2017 concerning the interaction of PCW components with polyphenols, with a particular focus on hemicellulose and pectin.

Grape polysaccharides: compositional changes in grapes and wines, possible effects on wine organoleptic properties, and practical control during winemaking

Polysaccharides present in grapes interact with wine sensory-active compounds (polyphenols and volatile compounds) via different mechanisms and can affect wine organoleptic qualities such as astringency, color and aroma. Studies on the role that grape polysaccharides play in wines are reviewed in this paper. First, the composition of grape polysaccharides and their changes during grape ripening, winemaking and aging are introduced. Second, different interaction mechanisms of grape polysaccharides and wine sensory-active compounds (flavanols, anthocyanins and volatiles) are introduced, and the possible effects on wine astringency, color and aroma caused by these interactions are illustrated. Finally, the control of the grape polysaccharide content in practice is discussed, including classical winemaking methods (applying different maceration enzymes, temperature control, co-fermentation, blending), modern vinification technologies (pulsed electric field, ultrasound treatment), and the development of new grape polysaccharide products.

Improved color stability of anthocyanins in the presence of ascorbic acid with the combination of rosmarinic acid and xanthan gum

This study investigated the protective effect and mechanism of action of combined use of rosmarinic acid (RA) and xanthan gum (XG) on the stability of anthocyanins (ACNs) in the presence of l-ascorbic acid (pH 3.0). The addition of RA and XG, alone and in combination, significantly enhanced the color stability of ACNs, and the combined use of RA and XG showed the best effect. FTIR, 1H NMR, AFM and computational molecular simulation analyses revealed that the improvement in ACN stability following the combined addition of RA and XG was due to intermolecular interactions such as hydrogen bonding and van der Waals forces. In the ACN-RA-XG ternary complexes, XG had stronger binding interactions with ACNs than RA. Our findings provide a valuable potential to enhance the stability of ACNs in the presence of ascorbic acid with the combined use of RA and XG.

Combination of copigmentation and encapsulation strategies for the synergistic stabilization of anthocyanins

Copigmentation and encapsulation are the two most commonly used techniques for anthocyanin stabilization. However, each of these techniques by itself suffers from many challenges associated with the simultaneous achievement of color intensification and high stability of anthocyanins. Integrating copigmentation and encapsulation may overcome the limitation of usage of a single technique. This review summarizes the most recent studies and their challenges aiming at combining copigmentation and encapsulation techniques. The effective approaches for encapsulating copigmented anthocyanins are described, including spray/freeze-drying, emulsification, gelation, polyelectrolyte complexation, and their combinations. Other emerging approaches, such as layer-by-layer deposition and ultrasonication, are also reviewed. The physicochemical principles underlying the combined strategies for the fabrication of various delivery systems are discussed. Particular emphasis is directed toward the synergistic effects of copigmentation and encapsulation, for example, modulating roles of copigments in the processes of gelation and complexation. Finally, some of the major challenges and opportunities for future studies are highlighted. The trend of integrating copigmentation and encapsulation has been just started to develop. The information in this review should facilitate the exploration of the combination of multistrategy and the fabrication of robust delivery systems for copigmented anthocyanins.

Preparation, characterization, antioxidant and anti-inflammatory activities of acid-soluble pectin from okra (Abelmoschus esculentus L.)

Currently, there are few studies on acid-soluble pectin from okra, especially in biological activity for antioxidant and anti-inflammatory. In this study, the antioxidant properties of acid-soluble okra pectin components and their anti-inflammatory were explored. Firstly, two acid-soluble okra pectic fractions, namely crude acid-soluble okra pectin (CAOP) and acid-soluble okra pectin (AOP), were obtained and exhibited structural and compositional variation. The two pectic fractions contained a low degree of esterification (42.0-46.5%) and a relatively high uronic acid content (31.6-37.3%). AOP was composed of galacturonic acid (79.1 mol/%), galactose (4.3 mol/%), rhamnose (14.5 mol/%) and xylose (2.1 mol/%), and the molecular weight was 92.8 kDa. Morphological and thermal properties of acid-soluble okra pectin components were also investigated. Compared to CAOP, AOP expressed better antioxidant activity, and suppressed the NO production in LPS-induced RAW 264.7 macrophages. All the above results indicated that AOP had the potential to act as a natural antioxidant or a functional anti-inflammatory food, which would broaden the development and utilization of okra resources.

Dendrimers as Color-Stabilizers of Pyranoanthocyanins: The Dye Concentration Governs the Host-Guest Interaction Mechanisms

Anionic dendrimers have recently emerged as hosts (H) for the color stabilization of the flavylium cation of anthocyanin guests (G). The interaction with a promising, more hydrophobic pyranoanthocyanin illustrates how the structure and concentration of the dye modulate the host-guest interaction mechanisms. NMR and UV-vis titrations (host over guest, from G/H ratio 2089 to 45) showed that at relatively low dendrimer-to-dye concentrations, ion pairs at the dendrimer periphery prevail over dye encapsulation. This promotes the deaggregation of the dye, not previously observed with anthocyanins, and related to the more hydrophobic nature of this dye (deshielding of the dye ¹H signals, higher T ₂ relaxation times, constant diffusion coefficient). As the dendrimer concentration increases, the dye encapsulation, earlier unseen with structurally simpler flavylium dyes, becomes dominant (shielding and broadening of the dye ¹H signals and lower T ₂ and diffusion coefficient). The interaction parameters of the encapsulation process (K ∼ 4.51 × 10⁴ M^-1, n ∼ 150) indicate the binding of ca. one pyranoanthocyanin molecule by each sulfate terminal group. Our results provide insights into the ability of dendrimers to host structurally diverse pyranoflavylium-based dyes and how the structure of the latter modulates the range of interactions involved. The encapsulation ability of this dendrimer to such pH-sensitive dyes is envisioned for the host-guest sensing applications such as pH-responsive systems used for example in food smart packaging.

The potential of anthocyanins in smart, active, and bioactive eco-friendly polymer-based films: A review

Among the bioactive compounds that are considered important for the food industry, anthocyanins, which are flavonoid compounds presenting antioxidant activity and are responsible for beneficial health effects, have received researchers' attention in the last decades. In addition, anthocyanins are highly reactive and can be used as indicators of foodstuff quality conditions, particularly as a packaging ingredient. Considering this line of work, the eco-friendly film is a novel packaging technology that arose from the concern to reduce non-renewable resources and their impact on the environment. These films can be vehicles for loading bioactive compounds such as anthocyanins. Among the contribution of films in the food industry, we can highlight several potential applications: i) smart film: assess food quality and safety, transmitting food information to consumers and increasing the reliability of their consumption without breaking the packaging; ii) active film: use to preserve food quality through the release of active agents; and iii) bioactive film: carry substances in desired concentrations until their controlled or rapid diffusion within the gastrointestinal tract so that they can promote its benefit to human health. Thus, this review presents anthocyanin extract's potential as a powerful tool to improve the development of eco-friendly films, directing its purpose to the application as smart, active, and bioactive films.

Revising the formation and electronic properties in flavylium derivatives. A theoretical tandem towards optimized DSSCs

A study of benzopyrylium derivatives obtained from a luminescent precursor, including the optical pathway, bonding analysis, and transmission properties, toward green energy applications.

Grape pectic polysaccharides stabilization of anthocyanins red colour: Mechanistic insights

Grape pectic polysaccharides-malvidin-3-O- β -d-glucoside binding was studied, aiming to unveil the impact of structural diversity of polysaccharides on anthocyanins-polysaccharides interactions. Polysaccharides were extracted with solutions of imidazole (ISP) and carbonate at 4 °C (CSP-4 °C) and room temperature (CSP-RT) and also recovered from the dialysis supernatant of the remaining cellulosic residue after the aqueous NAOH extraction of hemicellulosic polysaccharides (Sn-CR). Polysaccharides richer in homogalacturonan domains, like those present in the CSP-4 °C fraction had approximately 50-fold higher binding affinity to malvidin-3-O- β-d-glucoside, than polysaccharides with side chains (as ISP and CSP-RT extractable polysaccharides). CSP-4 °C polysaccharides showed a positive effect on malvidin-3-O- β-d-glucoside colour fading. Hydration equilibrium constant of malvidin-3-O- β-d-glucoside in the presence of CSP-4 °C polysaccharides was higher, showing the preferential stabilization of the flavylium cation. The results showed that anthocyanins colour stabilization can be promoted by pectic polysaccharide structures such as those extracted by cold carbonate.

Interactions between cell wall polysaccharides and polyphenols: Effect of molecular internal structure

Cell wall polysaccharides (CPSs) and polyphenols are major constituents of the dietary fiber complex in plant-based foods. Their digestion (by gut microbiota) and bioefficacy depend not only on their structure and quantity, but also on their intermolecular interactions. The composition and structure of these compounds vary with their dietary source (i.e., fruit or vegetable of origin) and can be further modified by food processing. Various components and structures of CPSs and polyphenols have been observed to demonstrate common and characteristic behaviors during interactions. However, at a fundamental level, the mechanisms that ultimately drive these interactions are still not fully understood. This review summarizes the current state of knowledge on the internal factors that influence CPS-polyphenol interactions, describes the different ways in which these interactions can be mediated by molecular composition or structure, and introduces the main methods for the analysis of these interactions, as well as the mechanisms involved. Furthermore, a comprehensive overview is provided of recent key findings in the area of CPS-polyphenol interactions. It is becoming clear that these interactions are shaped by a multitude of factors, the most important of which are the physicochemical properties of the partners: their morphology (surface area and porosity/pore shape), chemical composition (sugar ratio, solubility, and non-sugar components), and molecular architecture (molecular weight, degree of esterification, functional groups, and conformation). An improved understanding of the molecular mechanisms that drive interactions between CPSs and polyphenols may allow us to better establish a bridge between food processing and the bioavailability of colonic fermentation products from CPSs and antioxidant polyphenols, which could ultimately lead to the development of new guidelines for the design of healthier and more nutritious foods.

Characterization, antioxidant activities, and inhibition on α-glucosidase activity of corn silk polysaccharides obtained by different extraction methods

The polysaccharides (CSPw, CSPc, CSPa, and CSPu) were prepared by hot water extraction, acid-assisted extraction, alkaline-assisted extraction, and ultrasound-assisted extraction from corn silk, respectively. High performance gel permeation chromatography (HPGPC), fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) results indicated that the extraction methods had an obvious impact on the molecular weight, structure, and morphology of the CSPs. Among the four polysaccharides, CSPu showed the highest inhibitory α-glucosidase activity, which might be related to its smaller molecular weight. Furthermore, kinetics analyses revealed that CSPu had significant inhibition of α-glucosidase in a non-reversible and competitive manner. Fluorescence quenching analysis illustrated that the interaction mechanism of CSPu and α-glucosidase was claimed as a static quenching mechanism. Isothermal titration calorimetry (ITC) analysis showed that the main driving forces for the interaction of CSPu with α-glucosidase was hydrogen bonding and the binding interactions of them occurred spontaneously.

Preparation of Lipid-Soluble Bilberry Anthocyanins through Acylation with Cinnamic Acids and their Antioxidation Activities

To enable the use of anthocyanins in food with high oil content, bilberry anthocyanins were acylated with cinnamic acids to address their poor lipid solubility. Structural analyses based on Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ¹H nuclear magnetic resonance analyses indicated that cinnamic acids were efficiently grafted onto 6-OH of glucoside and galactoside and 5-OH of arabinose through an esterification reaction. The higher the dose of the acylating agent, the higher the acylation degree (AD) and the lower the total anthocyanidin content (TAC) of bilberry anthocyanins. An-Ci4 presented the highest AD value (6.61%), and An-Ci3 exhibited the lowest TAC value (50.16 mg/g). After acylating with lipophilic cinnamic acids, the lipid solubility of acylated bilberry anthocyanins significantly improved. The color of the native bilberry anthocyanin solution dissolved in ethyl acetate and dioxane was transparent. By contrast, the acylated anthocyanin solution dissolved in these solvents was unmistakably red. In terms of the antioxidant activity, acylated bilberry anthocyanins demonstrated inferior performance in 2,2-diphenyl-1-picrylhydrazyl (DPPH) clearance but a better inhibition ratio in β-carotene bleaching assay compared with native bilberry anthocyanins. As AD value increased, the DPPH clearance of acylated anthocyanins decreased and their inhibition ratio increased in β-carotene bleaching assay.