pH- and ionic strength-dependent interaction between cyanidin-3-O-glucoside and sodium caseinate

First insights into the binding mechanism and colour effect of the interaction of grape seed 11S globulin with malvidin 3-O-glucoside by fluorescence spectroscopy, differential colorimetry and molecular modelling

Recently, the search for alternative proteins endogenous to grapes to be used as wine colour protecting agents became an important research trend. In this study, the molecular interaction between the grape seed 11S globulin from winemaking by-product and malvidin-3-O-glucoside was investigated by fluorescence, differential colorimetry and molecular modelling. Fluorescence studies revealed the formation of grape seed protein- pigment complex whose KS was 8.5 × 104 M-1 and binding sites, n = 1.3. Malvidin-3-O-glucoside showed darker and more vivid bluish colour of in the presence of 11S globulin, suggesting the flavylium cation protection in a hydrophobic region of the protein. Docking analysis and molecular dynamics simulation indicated that malvidin-3-O-glucoside interacts mainly with the acidic subunit (40 kDa) of the 11S globulin monomer (60 kDa). An average of two hydrogen bonds and Van der Wall forces were the main interaction forces found for the protein-pigment complex, whose stability was confirmed by root-means-square deviation.

A comparative evaluation of anti-tumor activity following oral and intravenous delivery of doxorubicin in a xenograft model of breast tumor

Purpose

Natural materials have been extensively studied for oral drug delivery due to their biodegradability and other unique properties. In the current research, we fabricated sodium caseinate nanomicelles (NaCNs) using casein as a natural polymer to develop a controlled-release oral delivery system that would improve the therapeutic potential of doxorubicin (DOX) and reduce its toxicity.

Methods

DOX-loaded NaCNs were synthesized and thoroughly characterized, then subjected to in vivo anti-tumor evaluation and bio-distribution analysis in a 4T1-induced breast cancer model.

Results

Our findings indicated that the tumor would shrink by eight-fold in the group orally treated with DOX-NaCNs when compared to free DOX. The tumor accumulated drug 1.27-fold more from the orally administered DOX-NaCNs compared to the intravenously administered DOX-NaCNs, 6.8-fold more compared to free DOX, and 8.34-times more compared to orally administered free DOX. In comparison, the orally administered DOX-NaCNs lead to a significant reduction in tumor size (5.66 ± 4.36 mm3) compared to intravenously administered DOX-NaCNs (10.29 ± 4.86 mm3) on day 17 of the experiment. NaCNs were well tolerated at a single dose of 2000 mg/kg in an acute oral toxicity study.

Conclusion

The enhanced anti-tumor effects of oral DOX-NaCNs might be related to the controlled release of DOX from the delivery system when compared to free DOX and the intravenous formulation of DOX-NaCNs. Moreover, NaCNs is recognized as a safe and non-toxic delivery system with excellent bio-distribution profile and high anti-tumor effects that has a potential for oral chemotherapy.

Effects of organic acids on color intensification, thermodynamics, and copigmentation interactions with anthocyanins

Anthocyanins are attractive alternatives to synthetic colorants, but their low stability impedes practical applications. Intermolecular copigmentation can enhance both color intensity and stability. Herein, the copigmentation interactions of Kyoho grape skin anthocyanins (KSA) or cyanidin-3-O-glucoside (Cy-G) with organic acids were investigated. Color enhancement was evaluated at different acid molar ratios and treatment temperatures. The optimal copigmentation effects were observed for KSA/tannic acid (1:150) and Cy-G/tannic acid (1:100). Based on enthalpy variation, KSA/ferulic acid and Cy-G/ferulic acid exhibited the highest stability. The distinct color differences observed in the presence of different acids were attributed to structural effects. The influence of ferulic acid on various anthocyanins was also evaluated using theoretical approaches. Owing to steric hindrance, the acyl groups in KSA affected the spatial conformation, hydrogen bonding, and van der Waals interactions of the complexes. Further, hydroxyl groups decreased complex stability. These findings contribute to furthering the understanding of copigmentation effects.

Advances in dietary proteins binding with co-existed anthocyanins in foods: Driving forces, structure-affinity relationship, and functional and nutritional properties

Anthocyanins, which are the labile flavonoid pigments widely distributed in many fruits, vegetables, cereal grains, and flowers, are receiving intensive interest for their potential health benefits. Proteins are important food components from abundant sources and present high binding affinity for small dietary compounds, e.g., anthocyanins. Protein-anthocyanin interactions might occur during food processing, ingestion, digestion, and bioutilization, leading to significant changes in the structure and properties of proteins and anthocyanins. Current knowledge of protein-anthocyanin interactions and their contributions to functions and bioactivities of anthocyanin-containing foods were reviewed. Binding characterization of dietary protein-anthocyanins complexes is outlined. Advances in understanding the structure-affinity relationship of dietary protein-anthocyanin interaction are critically discussed. The associated properties of protein-anthocyanin complexes are considered in an evaluation of functional and nutritional values.

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.

Advances in preparation, interaction and stimulus responsiveness of protein-based nanodelivery systems

The improved understanding of the connection between diet and health has led to growing interest in the development of functional foods designed to improve health and wellbeing. Many of the potentially health-promoting bioactive ingredients that food manufacturers would like to incorporate into these products are difficult to utilize because of their chemical instability, poor solubility, or low bioavailability. For this reason, nano-based delivery systems are being developed to overcome these problems. Food proteins possess many functional attributes that make them suitable for formulating various kinds of nanocarriers, including their surface activity, water binding, structuring, emulsification, gelation, and foaming, as well as their nutritional aspects. Proteins-based nanocarriers are therefore useful for introducing bioactive ingredients into functional foods, especially for their targeted delivery in specific applications.This review focusses on the preparation, properties, and applications of protein-based nanocarriers, such as nanoparticles, micelles, nanocages, nanoemulsions, and nanogels. In particular, we focus on the development and application of stimulus-responsive protein-based nanocarriers, which can be used to release bioactive ingredients in response to specific environmental triggers. Finally, we discuss the potential and future challenges in the design and application of these protein-based nanocarriers in the food industry.

Covalent and non-covalent interactions of cyanidin-3-O-glucoside with milk proteins revealed modifications in protein conformational structures, digestibility, and allergenic characteristics

Currently, there is a need to explore the effects of different types of protein-anthocyanin complexations, as well as the possible changes in the nutrition and allergenicity of the formed complexes. Here, we systematically investigated the covalent and non-covalent interactions between cyanidin-3-O-glucoside (C3G) and two major milk proteins, α-casein (α-CN) and β-lactoglobulin (β-LG). Fluorescence quenching data showed that, under non-covalent conditions, C3G quenched the fluorescence of the two proteins via a static process, with the interaction forces being revealed; for covalent products, decreased fluorescence intensities were observed with red shifts in the λ_max. Multiple spectroscopic analyses implied that C3G-addition induced protein structural unfolding through transitions between the random coil and ordered secondary components. With a two-stage simulated gastrointestinal (GI) digestion model, it was seen that covalent complexes, not their non-covalent counterparts, showed reduced protein digestibility, ascribed to structural changes resulting in the unavailability of enzyme cleaving sites. The GI digests displayed prominent 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation-scavenging abilities (3.8-11.1 mM Trolox equivalents per mL digest), in contrast to the markedly reduced 1,1-diphenyl-2-picrylhydrazyl radical-scavenging capacities. Additionally, covalent protein-C3G complexes, but not their non-covalent counterparts, showed lower IgE-binding levels in comparison to the native control. This study provides new understanding for the development of anthocyanin-milk protein systems as functional ingredients with health-beneficial properties.

Thermal degradation of cyanidin-3-O-glucoside: Mechanism and toxicity of products

The thermal degradation behavior of cyanidin-3-O-gluoside (Cy3G) in nitrogen and air was studied using thermogravimetric analysis (TGA), thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatography/mass spectrometry (Py-GCMS). The results show that the thermal degradation of Cy3G in nitrogen and in air can be divided into three steps. The total degradation rate was 63.09% in nitrogen and 99.42% in air, and the total activation energy (E_a) was 65.85 and 80.98 kJ·mol^-1, respectively. The TG-FTIR analysis showed that Cy3G is significantly decomposed at 200-300 °C. The Py-GCMS analysis shows that the first step in the thermal degradation of Cy3G in nitrogen is the cleavage of glycosidic bonds to give cyanidin and glucoside. The glucoside and cyanidin then degrade further to give mainly low molecular weight compounds, together with furan derivatives, pyran derivatives and aromatic compounds. The phenols and furans found in the pyrolysis products are known to have a degree of toxicity.

Interactions between caseins and food-derived bioactive molecules: A review

Caseins are recognized as safe for consumption, abundant, renewable and have high nutritional value. Casein molecules are found in different aggregation states and their multiple binding sites offer the potential for delivering biomolecules with nutritional and/or health benefits, such as vitamins, phytochemicals, fibers, lipids, minerals, proteins, peptides, and pharmaceutical compounds. In the present review, we highlight the interactions between caseins and food-derived bioactive molecules, with a special focus on the aggregation states of caseins and the techniques used to produce and study the particles used for delivering. Research on interactions between caseins-minerals and casein-pharmaceutical molecules are not included here. This review aims to support the development of new and innovative functional foods in which caseins can be used as designed delivery systems.

Occurrence, environmental implications and risk assessment of Bisphenol A in association with colloidal particles in an urban tropical river in Malaysia

Phase distribution of emerging organic contaminants is highly influential in their presence, fate and transport in surface water. Therefore, it is crucial to determine their state, partitioning behaviour and tendencies in water environments. In this study, Bisphenol A was investigated in both colloidal and soluble phases in water. BPA concentrations ranged between 1.13 and 5.52 ng L⁻¹ in the soluble phase and n.d-2.06 ng L⁻¹ in the colloidal phase, respectively. BPA was dominant in the soluble phase, however, the colloidal contribution ranged between 0 and 24% which implied that colloids can play a significant role in controlling BPA’s transportation in water. Urban and industrial areas were the main sources of BPA while forest areas displayed lower levels outside the populated domains. pH levels were between 6.3 and 7.4 which might have affected BPA’s solubility in water to some extent. The particle size distribution showed that the majority of the particles in river samples were smaller than 1.8 µm in diameter with a small presence of nanoparticles. Zeta potential varied between − 25 and − 18 mV, and these negative values suggested instability of particles. Furthermore, BPA was positively correlated with BOD, COD and NH₃–N which might indicate that these organic compounds were released concurrently with BPA. RQ assessment showed low levels of risk towards algae and fish in the study area.

Nanoemulsions and acidified milk gels as a strategy for improving stability and antioxidant activity of yarrow phenolic compounds after gastrointestinal digestion

The aim of this study was to improve the stability and antioxidant activity of yarrow phenolic compounds upon an in vitro simulated gastrointestinal digestion. Therefore, two types of caseins-based delivery systems, sodium caseinate stabilized nanoemulsions (NEs) and glucono delta-lactone acidified milk gels (MGs), were formulated containing an ultrasound-assisted yarrow extract (YE) at two concentrations (1 and 2.5 mg/mL). Formulations with 1 mg/mL of YE were chosen based on their higher encapsulation efficiency to perform the in vitro digestion experiments. After digestion, YE-loaded NEs only partially protected phenolic compounds from degradation; meanwhile the phenolic composition of YE including in MGs after digestion was quite similar to undigested YE. Moreover, the antioxidant activity of MGs after digestion was higher than NEs digested samples, which confirms the higher protection of YE phenolic compound by the milk gels systems. This research demonstrated the potential use of acidified MGs as carriers to improve the stability and antioxidant activity of yarrow phenolic compounds. Therefore, these matrices could be employed to develop new dairy products enriched with phenolic compounds.

pH dependence of the binding interactions between humic acids and bisphenol A - A thermodynamic perspective

The wide application of bisphenol A (BPA) leads to the emergence of BPA residuals in natural water environments. Dissolved organic matter (DOM) existed in water can bind with BPA, hence influencing the migration and transformation of BPA in aquatic environments. pH is a crucial factor governing the binding interactions between DOM and BPA. However, the mechanisms driven the binding process under different pH conditions are still unclear. In this study, the interactions between BPA and humic acids (HA), a primary component of DOM, are investigated over a wide pH range of 3-12 by integrating fluorescence quenching, dynamic light scattering and microcalorimetry. pH dependence of the binding interactions between HA and BPA are interpreted from a thermodynamic perspective. The results indicate that HA can spontaneously interact with BPA to form a stable HA-BPA complex. With the increasing pH, the binding interactions change from entropy driven to entropy-enthalpy co-driven. Hydrophobic force dominate the binding interactions under acidic condition. The synergy of hydrophobic force and hydrogen bond promotes the binding process under neutral condition. Under alkaline conditions, electrostatic repulsion participates the binding process in addition to hydrophobic force and hydrogen bond, weakening the binding strength. Therefore, neutral pH is favorable for HA to bind with BPA, consequently enhancing the dissolution of BPA in natural water bodies. The results are beneficial to better understand the pH dependent distribution of BPA in aquatic environments.

Inhibition of urease activity by humic acid extracted from sludge fermentation liquid

This study achieved effective extraction of humic acid from sludge fermentation liquid, and the inhibition of urease activity by the extract were investigated in the urea decomposition. The addition of extract could remarkably inhibit urease activity and extend the releasing time of ammonia nitrogen. The interaction between the extract and urease took times, and the inhibition was irreversible. The results of fluorescence analysis revealed that the inhibition of urease activity was correlated to the amount of humic acid extracted. The mechanisms of inhibition were proposed that the functional groups of humic acid might interact with the thiol group of urease and formed a larger particle size of complex to inhibit the activity of urease. The extraction of humic acid from sludge fermentation liquid can not only recover the resource from the fermentation liquid, but also provide a potential urease inhibitor for the sustained-release effect of the soil organic nitrogen fertilizer.

The Chemical Reactivity of Anthocyanins and Its Consequences in Food Science and Nutrition

Owing to their specific pyrylium nucleus (C-ring), anthocyanins express a much richer chemical reactivity than the other flavonoid classes. For instance, anthocyanins are weak diacids, hard and soft electrophiles, nucleophiles, prone to developing π-stacking interactions, and bind hard metal ions. They also display the usual chemical properties of polyphenols, such as electron donation and affinity for proteins. In this review, these properties are revisited through a variety of examples and discussed in relation to their consequences in food and in nutrition with an emphasis on the transformations occurring upon storage or thermal treatment and on the catabolism of anthocyanins in humans, which is of critical importance for interpreting their effects on health.