Polyphenol-protein Complexes Research Articles

Construction and characteristics of EGCG-porcine serum albumin pickering emulsion: Based on noncovalent interactions mechanism

Pickering emulsion prepared by the interaction between polyphenols and protein can improve the stability of protein-based emulsion. The purpose of this study was to explore the complex formation mechanism of epigallocatechin gallate (EGCG)-porcine serum albumin (PSA) complex and the preparation of food-grade Pickering emulsion. By the UV and fluorescence spectral analysis, it was found that EGCG has an obvious fluorescence quenching effect on PSA, mainly static quenching. The results of synchronous, three-dimensional fluorescence and FT-IR spectroscopy showed that the hydrophobic microenvironment of aromatic amino acids and the secondary structure of PSA changed after EGCG was added. The results of molecular docking examined that EGCG and PSA form more stable complexes due to hydrogen bonds, and the binding energy was −4.43 kcal /mol. Compared with the PSA emulsion, the successfully prepared EGCG-PSA Pickering emulsion had smaller droplets and no obvious color in CLMS. The Pickering emulsion of EGCG-PSA had strong emulsification and high viscosity, which belonged to pseudoplastic non-Newtonian fluid. In addition, the free fatty acids release rate of EGCG-PSA Pickering emulsion was decreased by 9.9 %. The antioxidant performance of the EGCG-PSA Pickering emulsion was improved, and the DPPH radical scavenging rate and the ABTS+ radical scavenging rate reached the highest, which were 93.72 % and 57.16 % respectively. This study provides important insights into the interaction between EGCG and PSA, and a reference for the development of polyphenol-protein complex Pickering emulsion in food, medicine, cosmetics, and other fields.

A prediction method of interaction based on Bilinear Attention Networks for designing polyphenol-protein complexes delivery systems

Polyphenol-protein complexes delivery systems are gaining attention for their potential health benefits and food industry development. However, creating an ideal delivery system requires extensive wet-lab experimentation. To address this, we collected 525 ligand-protein interaction data pairs and established an interaction prediction model using Bilinear Attention Networks. We utilized 10-fold cross validation to address potential overfitting issues in the model, resulting in showed higher average AUROC (0.8443), AUPRC (0.7872), and F1 (0.8164). The optimal threshold (0.3739) was selected for the model to be used for subsequent analysis. Based on the model prediction results and optimal threshold, by verifying experimental analysis, the interaction of paeonol with the following proteins was obtained, including bovine serum albumin (lgKa = 6.2759), bovine β-lactoglobulin (lgKa = 6.7479), egg ovalbumin (lgKa = 5.1806), zein (lgKa = 6.0122), bovine α-lactalbumin (lgKa = 3.9170), bovine lactoferrin (lgKa = 4.5380), the first four proteins are consistent with the predicted results of the model, with lgKa >5. The established model can accurately and rapidly predict the interaction of polyphenol-protein complexes. This study is the first to combine open ligand-protein interaction experiments with Deep Learning algorithms in the food industry, greatly improving research efficiency and providing a novel perspective for future complex delivery system construction.

Extending the freshness of tilapia surimi with pulsed electric field modified pea protein isolate-EGCG complex

The development of natural polyphenol-protein complexes for preserving surimi holds great promise. The effects of pea protein isolate (PPI) - (−)-Epigallocatechin-gallate (EGCG) non-covalent and covalent complexes modified by pulsed electric field (PEF) on the preservation of tilapia surimi were evaluated. Results showed that the PEF-treated PPI-EGCG non-covalent complex extended the shelf life of surimi by more than 6 days. This complex reduced the microbial activity and delayed the lipid and protein oxidation of surimi during chilled storage. Total viable count (TVC), thiobarbituric acid reactive substances (TBARS), and total volatile base nitrogen (TVB-N) of surimi with PEF-treated PPI-EGCG non-covalent complex on day 15 were 31.65 %, 68.67 %, and 54.46 % lower than untreated surimi, respectively. Moreover, the rate of colour deterioration and off-odour development were also delayed. The major products of lipid oxidation in surimi were reduced by 37.91 % for hexanal, 43.14 % for pentanal, 73.24 % for 1-octen-3-ol, and 39.32 % for 1-penten-3-ol on day 15. Structural analyses and computer simulations revealed that PEF was able to unfold the structure of PPI, thereby exposing more binding sites for EGCG. PEF-treated PPI-EGCG non-covalent complex allowed the slow dissociation of EGCG from PPI and maintained the antimicrobial and antioxidant activities of EGCG in a long storage time. Therefore, PEF-treated PPI-EGCG non-covalent complex was considered as a potential preservative in fish and fish products.

The differential non-covalent binding of epicatechin and chlorogenic acid to ovotransferrin and the enhancing efficiency of immunomodulatory activity

Seeking safe and environmentally friendly natural immunomodulators is a pressing requirement of humanity. This study investigated the differential binding characteristics of two polar polyphenols (PP), namely epicatechin (EC) and chlorogenic acid (CA), to ovotransferrin (OVT), and explored the relationship between structural transformations and immunomodulatory activity of OVT-PP complexes. Results showed that CA exhibited a stronger affinity for OVT than EC, mainly driven by hydrogen bonds and van der Waals forces. Complexation-induced conformational variations in OVT, including static fluorescence quenching, increased microenvironment polarity surrounding tryptophan and tyrosine residues, and the transition from disordered α-helix to stable β-sheet. Furthermore, the structural conformation transformation of OVT-PP complexes facilitated the enhancement of immunomodulatory activity, with the OVT-CA (10:2) complex demonstrating the best immunomodulatory activity. Principal component analysis (PCA) and Pearson correlation analysis revealed the immunomodulatory activities of the OVT-PP complexes were influenced by surface hydrophobicity (negatively correlated), β-sheet percentage and polyphenol binding constants. It could be inferred that PP complexation increased the surface polarity of OVT, consequently enhancing its immunomodulatory activity by promoting cell membrane affinity and antigen recognition. This study provides valuable guidance for effectively utilizing polyphenol-protein complexes in enhancing immunomodulatory activity.

Molecular Mechanisms and Applications of Polyphenol-Protein Complexes with Antioxidant Properties: A Review.

Proteins have been extensively studied for their outstanding functional properties, while polyphenols have been shown to possess biological activities such as antioxidant properties. There is increasing clarity about the enhanced functional properties as well as the potential application prospects for the polyphenol-protein complexes with antioxidant properties. It is both a means of protein modification to provide enhanced antioxidant capacity and a way to deliver or protect polyphenols from degradation. This review shows that polyphenol-protein complexes could be formed via non-covalent or covalent interactions. The methods to assess the complex's antioxidant capacity, including scavenging free radicals and preventing lipid peroxidation, are summarized. The combination mode, the type of protein or polyphenol, and the external conditions will be the factors affecting the antioxidant properties of the complexes. There are several food systems that can benefit from the enhanced antioxidant properties of polyphenol-protein complexes, including emulsions, gels, packaging films, and bioactive substance delivery systems. Further validation of the cellular and in vivo safety of the complexes and further expansion of the types and sources of proteins and polyphenols for forming complexes are urgently needed to be addressed. The review will provide effective information for expanding applications of proteins and polyphenols in the food industry.

Reducing the Flocculation of Milk Tea Using Different Stabilizers to Regulate Tea Proteins

The regulation of flocs derived from polyphenol-protein formation in milk tea has not been fully explored. In this study, the flocculation of milk tea was regulated by adding 10 kinds of stabilizers with different characteristics. The stability coefficient and centrifugal precipitation rate were used as indexes. The optimal concentration ratio of the complex stabilizer was identified using the response surface methodology (RSM), being 0.04% for Arabic gum, 0.02% for β-cyclodextrin and 0.03% for Agar. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the characteristics of different stabilizers in milk tea, and our findings were as follows: (1) The relative strength of the peaks in different stable systems was different. The absorption peaks were mainly near the wave numbers 3376 cm-1, 2928 cm-1, 1655 cm-1, 1542 cm-1, 1408 cm-1, 1047 cm-1 and 925 cm-1. (2) The milk tea system was an amorphous structure. The diffraction peak of the composite system was observed to be about 20°. The crystallinity of the milk tea in the compound group was 33.16%, which was higher than that of the blank group (9.67%). (3) The compound stabilizer reduced flocculation, and the stabilizing agents improved the surface order of milk tea. These results indicate that the combination of polysaccharide stabilizers (Arabic gum and agar) and oligosaccharide stabilizers (β-CD) in certain proportions can regulate the flocculation of milk tea and improve its stability. The potential research avenues involving polyphenol-protein complex instability systems and their applications in food development are expanded by this work.

Effect of Lonicera edulis polysaccharide on reducing oral dyeing of lonicera edulis juice

Fluorescence spectroscopy, particle size determination, and potential analysis were exploited to elucidate the effect of Lonicera edulis polysaccharide on polyphenol protein. The results revealed that Lonicera edulis polysaccharides mediated the binding of polyphenols and proteins through competition and formation of ternary complexes and were also able to enhance the stability of the polyphenol-protein complex solution system. A certain electrostatic effect was also present in the process simultaneously. As confirmed by the dyeing test, to improve oral dyeing, the optimum conditions of adding polysaccharide, pectin, and casein were as follows: the dosage of the polysaccharide group was 1.2 mg/mL, coloring time was 100 min, pH value was 4.0. Pectin group added 0.8 mg/mL with coloring time 80 min, pH 5.0. The addition of casein was 1.2 mg/mL; the coloring time was 100 min with pH 5.0. The sample juice substantiated a significant improvement in the dyeing of porcine tongue mucosa. Under the optimal conditions, microscopic observation validates that the mucosal color of the porcine tongue epidermis was closer to that of unstained porcine tongue epidermis, which significantly improved astringency and oral staining.

Insights into interactions between food polyphenols and proteins: An updated overview

Polyphenols are widely distributed natural products, investigated intensively due to their health-beneficial effects and prevention of several human diseases. It is well known that polyphenols can easily form complexes with proteins in food processing and human digestion, leading to changes in the conformation and functionality of polyphenols and proteins. On the basis of dividing the common polyphenols into flavonoids, phenolic acids, and tannins, this paper reviews the progress and application of polyphenol–protein interactions during the past decade. Accordingly, this review might provide a better understanding on the mechanism of polyphenol–protein interactions, which is expected to provide guidance for food processing and studying on health effects of polyphenol compounds in the future. Novelty impact statement The interactions of flavonoids, phenolic acids, and tannins with proteins were reviewed. Reversible interactions are the main form of polyphenol–protein interactions, which are mainly attributed to hydrogen and hydrophobic bonding. Besides, the health effects of polyphenol–protein complexes mainly include the inhibition of protease and toxic protein aggregation.

Noncovalent Interactions of Sea Buckthorn Polyphenols with Casein and Whey Proteins: Effect on the Stability, Antioxidant Potential, and Bioaccessibility of Polyphenols

In this work, effect of casein and whey protein interaction on the stability, antioxidant potential, and bioaccessibility of sea buckthorn polyphenols was investigated. The results revealed that casein–polyphenol and whey protein–polyphenol interaction both decreased the in vitro antioxidant capacity of polyphenols. On the other hand, the protein–polyphenol complexes increased the stability of sea buckthorn polyphenols during simulated in vitro digestion. Moreover, both the casein–polyphenol and whey protein–polyphenol complexes exhibited an increased bioaccessibility of polyphenols (60.97–64.97%) in comparison to that of free polyphenolic extract (40.01%). The main bonding force between sea buckthorn polyphenols and the proteins was found to be a hydrophobic interaction, as revealed by ATR-FTIR, UV–vis, and fluorescence spectroscopy. The particle size of casein–polyphenol and whey protein–polyphenol complexes was in the nanosize region (650–983 nm). The low span factors of polyphenol–protein complexes revealed the narrow range of particle size distribution and thus more homogeneity in the particle size. This finding highlights that the interaction between casein and whey proteins with sea buckthorn polyphenols could protect these bioactive compounds against the influence of simulated digestion.

Bioactive coconut protein concentrate films incorporated with antioxidant extract of mature coconut water

Coconut is a very important fruit worldwide. Coconut milk cake and mature coconut water (CW) are the by-products from coconut processing. Therefore, it is of interest to exploit coconut milk cake and CW as a source of protein and antioxidant, respectively. In particular, antioxidant compounds from CW were extracted using a solvent (acetone and diethyl ether) and the evaporation compared with coconut water concentrate (CWC) which was extracted using evaporation. CWC had a 4-times higher total phenolic content than that of CW. Even though the solvent extract had a higher total phenolic content than the evaporation-only extract, the antioxidant capacity of the solvent extract of CWC and the evaporation-only (CWC) was not significantly different. Moreover, using CW as a solvent also reduced the amount of glycerol needed to form a satisfactory coconut protein film. The use of CW as a solvent and the incorporation of CWC significantly increased the film solubility and water vapor permeability but improved the film mechanical properties. The total phenolic content and antioxidant capacity increased in protein films incorporated with CWC and using CW as a solvent. Fourier transform infrared spectroscopy showed interactions among the antioxidant compounds from CW, CWC and protein. The formation of a polyphenol-protein complex doubled the film elongation. Thus, the coconut protein film produced using CW as a direct solvent and incorporated with CWC can provide an environmentally friendly active packaging material for agricultural and food product applications.

Dynamics of bacterial and archaeal amoA gene abundance after additions of organic inputs combined with mineral nitrogen to an agricultural soil

Dynamics of ammonia-oxidizing bacterial (AOB) and archaeal (AOA) abundance was assayed in a tropical Humic Nitisol during two cropping seasons of a long-term field experiment situated in the central highlands of Kenya. Since 2002, soils were treated yearly with biochemically contrasting organic inputs (4 Mg C ha−1 year−1) of Tithonia diversifolia (TD; C/N ratio: 13; lignin: 8.9 %; polyphenols: 1.7 %), Calliandra calothyrsus (CC; 13; 13; 9.4) and Zea mays (ZM; 59; 5.4; 1.2) combined with and without 120 kg CaNH4NO3 ha−1 season−1. In 2012 and 2013, soils (0–15 cm) were sampled at young growth (EC30) and flowering (EC60) stages of maize and subjected to DNA-based amoA gene quantification. ZM and TD increased AOB abundance by 9 and 19 %, respectively, compared to CC, while AOA remained unaffected. This was ascribed to high organic N in TD and lower lignin and polyphenol contents in ZM than in CC. In CC, formation of polyphenol-protein complexes limited microbial access to N. Sole use of mineral N or its combination with organic inputs decreased AOA abundance by 35 % but not AOB as a consequence of pH reduction by mineral N. Overall, AOB was more responsive than AOA to input quality that became most pronounced under optimal soil moisture conditions found in 2013 and at EC60 in 2012. We recommend prolonged study periods, considering also rRNA-based analyses to explore the dynamics of active nitrifying communities as a consequence of interrelations of contrasting organic inputs, crop growth stages and seasonality in agricultural soils.

Response of ammonia-oxidizing bacteria and archaea to biochemical quality of organic inputs combined with mineral nitrogen fertilizer in an arable soil

There exists a considerable knowledge gap about the effect of biochemical quality of organic inputs and their combination with inorganic N on abundance and community composition of ammonia-oxidizing archaea (AOA) and bacteria (AOB). Here, we investigated in a Humic Nitisol of 10-year old field experiment in Kenya the effect of contrasting organic inputs (i.e., Tithonia diversifolia (TD; C/N ratio: 13, Lignin: 8.9%; Polyphenols: 1.7%), Calliandra calothyrsus (CC; 13; 13; 9.4) and Zea mays (ZM; 59; 5.4; 1.2); rate of 4MgCha−1year−1) combined with mineral N fertilizer (120kg CaNH4NO3ha−1 growing season−1) on amoA gene-based abundance (i.e., functional potential) and community composition of AOB and AOA. AOB abundance was significantly lower in CC and ZM compared to TD, whereas AOA abundance was significantly lower in CC compared to ZM and TD. This reduction was attributed to a considerable N stress induced by limited organic N availability in ZM and polyphenol-protein complexes in CC. High abundance of AOA under ZM was attributed to their affinity to ammonium under N limiting conditions. Abundance shifts matched observed community composition differences between TD versus ZM (AOB) as well as TD versus ZM and CC (AOA). Mineral N irrespective of organic input type depressed abundance of AOA, but not AOB. This implied utilization of ammonium from fertilizer and organic N by AOB, while AOA mainly utilized ammonium from organic N. Our findings suggested input type dependent effects on AOB/AOA abundance and community composition, but influence of other factors such as soil type, seasonality and crop growth stages remain uncertain. These factors should not only be studied on basis of the functional potential of ammonia oxidizing prokaryotes as given in this study, but also by rRNA analyses to capture the active proportion of existent AOB and AOA.

Polyphenol-Protein Complexes and Their Consequences for the Redox Activity, Structure and Function of Honey. A Current View and New Hypothesis – a Review

There is increasing evidence that protein complexation by honey polyphenols is changing honey structure and function. This relatively less investigated fi led of honey research is presented in a context of known mechanism of formation of the stable polyphenol-protein complexes in other foods. At a core of these interactions lies the ability of polyphenols to form non-covalent and covalent bonds with proteins leading to transient and/or irreversible complexes, respectively. Honey storage and thermal processing induces non-enzymatic oxidation of polyphenols to reactive quinones and enables them to form covalent bonds with proteins. In this short review, we present data from our laboratory on previously unrecognized types of protein-polyphenol complexes that differed in size, stoichiometry, and antioxidant capacities, and the implications they have to honey antioxidant and antibacterial activities. Our intent is to provide a current understanding of protein-polyphenol complexation in honey and also some new thoughts /hypotheses that can be useful in directing future research.

Lasting influence of biochemically contrasting organic inputs on abundance and community structure of total and proteolytic bacteria in tropical soils

The SOM field experiments in Kenya, which have been initiated in 2002 on two contrasting soils (clayey Humic Nitisol (sand: 17%; silt: 18%; clay: 65%) at Embu, sandy Ferric Alisol (sand: 66%; silt: 11%; clay: 22%) at Machanga), were used for exploring the effect of nine year annual application of biochemically contrasting organic inputs (i.e., Zea mays (ZM; C/N ratio: 59; (lignin + polyphenols)-to-N ratio: 9.8); Tithonia diversifolia (TD; 13; 3.5); Calliandra calothyrsus (CC; 13; 6.7)) on the soil bacterial decomposer community. Soil samples were taken at the onset of the rainy season before application of fresh organic inputs in March 2011. We studied the abundance (quantitative PCR) and community structure (T-RFLP analysis) of the total (i.e., 16S rRNA gene) and specifically proteolytic (i.e., npr gene encoding neutral metalloproteases) bacteria. Alterations of the soil microbial decomposer community were related to differences of quantity (i.e., soil carbon (TC)) and particularly composition of SOC, where mid-infrared spectroscopic (DRIFTS) information, and contents of extractable soil polyphenol (PP) and the newly introduced PP-to-TC ratio served as SOC quality indicators. For total bacteria, effect of organic input quality was minor in comparison to the predominant influence of soil texture. Elevated soil PP content, driven by polypheneol rich organic inputs, was not suppressive for overall bacterial proliferation, unless additional decomposable C substrates were available as indicated by PP-to-TC ratios. In contrast to the total bacterial community, biochemical quality of organic inputs exposed a stronger effect on functionally specialized bacterial decomposers, i.e., proteolytic bacteria. The npr gene abundance was depressed in the TD treated soils as opposed to soils receiving CC, and showed a positive correlation with soil PP. It was suggested that the high presence of lignin and polyphenol relative to the N content in organic inputs was increasing the npr gene abundance to counteract most likely the existence of polyphenol–protein complexes aggravating protein degradation. We concluded from our study that integration of spectroscopic, geochemical (i.e., soil PP) and molecular soil data provides a novel pathway to enhance our understanding of the lasting effect of organic input quality induced SOC quality changes on bacterial decomposers and particularly proteolytic bacteria driving soil organic N cycling.

Artemisia dracunculus L. polyphenols complexed to soy protein show enhanced bioavailability and hypoglycemic activity in C57BL/6 mice

ObjectiveScientifically validated food-based interventions are a practical means of addressing the epidemic of metabolic syndrome. An ethanolic extract of Artemisia dracunculus L. (PMI-5011) containing bioactive polyphenols, such as 2′, 4′–dihydroxy-4-methoxydihydrochalcone (DMC-2), improved insulin resistance in vitro and in vivo. Plant polyphenols are concentrated and stabilized when complexed to protein-rich matrices, such as soy protein isolate (SPI), which act as effective food-based delivery vehicles. The aim of this study was to compare the bioaccessibility, bioavailability, and efficacy of polyphenols extracted from A. dracunculus and delivered as PMI-5011 (ethanolic extract alone), formulated with the non-food excipient Gelucire®, (5011- Gelucire), or sorbed to SPI (5011-Nutrasorb®). MethodsPMI-5011, 5011-Gelucire or 5011-Nutrasorb each containing 162 μg of DMC-2 was delivered to the TNO intestinal model-1 of the human upper gastrointestinal tract to compare the effect of delivery vehicle on DMC-2 bioaccessibility. C57BL6/J mice were orally administered 5011-Nutrasorb or PMI-5011 to compare effects of polyphenol–protein complexation on acute hypoglycemic activity and bioavailability of DMC-2 in serum. ResultsAt 500 mg/kg, 5011-Nutrasorb and PMI-5011 had similar hypoglycemic activity in a high-fat diet-induced diabetes mouse model despite the fact that 5011-Nutrasorb delivered 15 times less DMC-2 (40 versus 600 μg/kg). This can be partially explained by eight times greater DMC-2 absorption into serum from 5011-Nutrasorb than from PMI-5011. TNO intestinal model-1 experiments confirmed higher total bioaccessibility of DMC-2 in vitro when delivered in 5011-Nutrasorb (50.2%) or Gelucire-5011 (44.4%) compared with PMI-5011 (27.1%; P = 0.08). ConclusionComplexation with soy protein makes antidiabetic A. dracunculus polyphenols more bioavailable and bioaccessible.

Binding Sites of Resveratrol, Genistein, and Curcumin with Milk α- and β-Caseins

The binding sites of antioxidant polyphenols resveratrol, genistein, and curcumin are located with milk α- and β-caseins in aqueous solution. FTIR, CD, and fluorescence spectroscopic methods and molecular modeling were used to analyze polyphenol binding sites, the binding constant, and the effects of complexation on casein stability and conformation. Structural analysis showed that polyphenols bind casein via hydrophilic and hydrophobic interactions with the number of bound polyphenol molecules (n) 1.20 for resveratrol, 1.42 for genistein, and 1.43 for curcumin with α-casein and 1.14 for resveratrol, 1.27 for genistein, and 1.27 for curcumin with β-casein. The overall binding constants of the complexes formed are K(res-α-casein) = 1.9 (±0.6) × 10(4) M(-1), K(gen-α-casein) = 1.8 (±0.4) × 10(4) M(-1), and K(cur-α-casein) = 2.8 (±0.8) × 10(4) M(-1) with α-casein and K(res-β-casein) = 2.3 (±0.3) × 10(4) M(-1), K(gen-β-casein) = 3.0 (±0.5) × 10(4) M(-1), and K(cur-β-casein) = 3.1 (±0.5) × 10(4) M(-1) for β-casein. Molecular modeling showed the participation of several amino acids in polyphenol-protein complexes, which were stabilized by the hydrogen bonding network with the free binding energy of -11.56 (resveratrol-α-casein), -12.35 (resveratrol-β-casein), -9.68 (genistein-α-casein), -9.97 (genistein-β-casein), -8.89 (curcumin-α-casein), and -10.70 kcal/mol (curcumin-β-casein). The binding sites of polyphenols are different with α- and β-caseins. Polyphenol binding altered casein conformation with reduction of α-helix, indicating a partial protein destabilization. Caseins might act as carriers to transport polyphenol in vitro.

Probing the binding sites of resveratrol, genistein, and curcumin with milk β-lactoglobulin

We determined the binding sites of curcumin (cur), resveratrol (res), and genistein (gen) with milk β-lactoglobulin (β-LG) at physiological conditions. Fourier transform infrared spectroscopy, circular dichroism, and fluorescence spectroscopic methods as well as molecular modeling were used to determine the binding of polyphenol–protein complexes. Structural analysis showed that polyphenols bind β-LG via both hydrophilic and hydrophobic contacts with overall binding constants of Kcurcumin–β-LG = 4.4 (± .4) × 104 M−1, Kresveratrol–β-LG = 4.2 (± .2) × 104 M−1, and Kgenistein–β-LG = 1.2 (± .2) × 104 M−1. The number of polyphenol molecules bound per protein (n) was 1 (cur), 1.1 (res), and 1 (gen). Molecular modeling showed the participation of several amino acid residues in polyphenol–protein complexation with the free binding energy of −12.67 (curcumin–β-LG), −12.60 (resveratrol–β-LG), and −10.68 kcal/mol (genistein–β-LG). The order of binding was cur > res > gen. Alteration of the protein conformation was observed in the presence of polyphenol with a major reduction of β-sheet and an increase in turn structure, causing a partial protein structural destabilization. β-LG might act as a carrier to transport polyphenol in vitro.

Bovine Serum Albumin Significantly Improves the DPPH Free Radical Scavenging Potential of Dietary Polyphenols and Gallic Acids

Polyphenol-protein interaction (PPI) is reversible in that polyphenol-protein complex can be dissociated and release the free polyphenols. The aim of this study is to evaluate the contribution of polyphenol-protein interaction on improving the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging capacity of polyphenols. The DPPH radical scavenging potential of polyphenols was determined from 1 to 7 days under aerobic condition. The DPPH radical scavenging capacity of polyphenols depended on the structures of dietary polyphenols and gallic acids. The DPPH radical scavenging percentages of Group H polyphenols were weakened when kept in room temperature from 1 to 7 days. BSA rapid weakened the DPPH radical scavenging activity of polyphenols on the first day. However, the DPPH scavenging capacities of polyphenols in the presence of BSA overwhelmingly improved with increasing time. These results illustrated that BSA not only prolongs the effective time, but also improved the DPPH radical scavenging potential of polyphenols. The increasing DPPH scavenging percentages of polyphenols slightly decreased with increased affinities of BSA-polyphenol complexes.

Recent developments on polyphenol–protein interactions: effects on tea and coffee taste, antioxidant properties and the digestive system

Tea and coffee are widely consumed beverages across the world and they are rich sources of various polyphenols. Polyphenols are responsible for the bitterness and astringency of beverages and are also well known to impart antioxidant properties which is beneficial against several oxidative stress related diseases like cancer, cardiovascular diseases, and aging. On the other hand, proteins are also known to display many important roles in several physiological activities. Polyphenols can interact with proteins through hydrophobic or hydrophilic interactions, leading to the formation of soluble or insoluble complexes. According to recent studies, this complex formation can affect the bioavailability and beneficiary properties of both the individual components, in either way. For example, polyphenol-protein complex formation can reduce or enhance the antioxidant activity of polyphenols; similarly it can also affect the digestion ability of several digestive enzymes present in our body. Surprisingly, no review article has been published recently which has focused on the progress in this area, despite numerous articles having appeared in this field. This review summarizes the recent trends and patterns (2005 onwards) in polyphenol-protein interaction studies focusing on the characterization of the complex, the effect of this complex formation on tea and coffee taste, antioxidant properties and the digestive system.

Effect of Milk and Brewing Method on Black Tea Catechin Bioaccessibility

The aim of this study was to investigate whether milk reduces the bioaccessibility of tea catechins, which would compromise tea beneficial effects ascribed to polyphenols. Adding milk to black tea has been shown to lead to polyphenol-protein complexes. So far, data on the intestinal stability of polyphenol-protein complexes are scarce. English black tea (0.93 ± 0.06 mol/L total catechins) and Indian black tea (1.83 ± 0.08 mol/L catechins) were prepared with skimmed or full-fat milk and subjected to simulated gastric, small intestinal, and brush border digestion. Adding milk (5.6-40%) to tea results in a decrease of total catechin (TCAT) recovery. However, the bioaccessibilities of TCAT of tea with milk versus tea controls were comparable (p > 0.05). The type of milk did not influence TCAT recovery during all digestive stages (p > 0.05). Polyphenol-protein complexes are degraded during digestion. It is very unlikely that consumption of tea with or without milk will result in differences in catechin plasma concentration.