Procyanidin Research Articles

Inhibitory effects of polyphenols on the Maillard reaction in low lactose milk and the underlying mechanism

In this study, low lactose milk (LLM) was heat-treated under different conditions and stored at 4, 25 and 37°C for 15 d, after which the changes in the Maillard reaction (MR) of LLM were investigated. The contents of α-dicarbonyl compounds and 5-hydroxymethylfurfural(5-HMF) in LLM after the addition of polyphenols were determined via HPLC, and the inhibitory effects of 3 different concentrations of epigallocatechin gallate (EGCG), dihydromyricetin (DMY), and procyanidin (PC) on the MR of LLM were studied. The fluorescence intensity of LLM was measured at 290, 300 and 310 K, the fluorescence quenching types and binding constants of PC on casein were investigated, and thermodynamic analysis was carried out. These results suggest that the optimal heat treatment conditions were 80°C for 15 s and that the optimal storage conditions were 4°C. In the α-dicarbonyl compound capture and 5-HMF inhibition tests, PC had the greatest inhibitory effect at a concentration of 0.2 mg/mL, with an inhibition rate of 48.19%. Therefore, PC is more stable than the other 2 polyphenols. The mechanism of inhibition involves the formation of matrix complexes between PC and casein in LLM, resulting in static quenching of the LLM and thus a reduction of the inhibitory effect. The thermodynamic analysis revealed that the binding of PC to casein was an exothermic reaction, and the combination of the 2 was driven mainly by hydrogen bonding and van der Waals forces. This study lays a theoretical foundation for the development of LLM.

Optimization of pH-responsive microgel for the co-delivery of Weizmannia coagulans and procyanidins to enhance survival rate and tolerance

The purpose of this study was to prepare a pH-responsive microgel for co-delivering Weizmannia coagulans 99 (BC99) and procyanidins (PCs) to enhance the survival rate and tolerance of probiotics in complex micro-environment. The effects of different concentrations of PCs on the properties of microgels were optimized, and found that the spherical microgels had higher encapsulation efficiency (90.27 ± 2.51 %) and smaller size when the concentration of PCs was 20 μg/mL. The interaction among PCs, pectin and protein could effectively improve the survival rate of BC99 under different pH, bile salt, digestive enzyme and temperature conditions, maintain their stability in acidic gastric fluid, and realize the release of probiotics in neutral intestinal fluid. Moreover, the microgel was able to protect BC99 against H2O2 and antibiotics. This work provides a pH-responsive co-loaded microgels for BC99 and PCs, and has the potential in the loading and delivery of other probiotics and polyphenols.

Litchi Procyanidins Ameliorate DSS-Induced Colitis through Gut Microbiota-Dependent Regulation of Treg/Th17 Balance.

Ulcerative colitis (UC) is a common chronic, relapsing inflammatory bowel condition. Procyanidins (PC) are known for their antiangiogenic, anti-inflammatory, antioxidant, and antimetastatic properties. However, there is comparatively limited information on how PC interacts with UC. In this study, 5 mg/10 mL/kg body weight of PC was administered to mice with dextran sulfate sodium (DSS)-induced colitis mice. PC treatment prolonged the survival period of mice, ameliorated UC symptoms, reduced damage to the intestinal mucosal barrier, and increased the protein expression of ZO-1 and occludin in the DSS-treated mice. Importantly, PC treatment significantly reduced gene expression related to Th17 cell differentiation, including STAT3, SMAD3, TGF-β, and JAK1. The results of the flow cytometry analysis indicated significant increase in the number of Treg cells and a concomitant decrease in the proportion of Th17 cells in the colon following PC treatment. Additionally, PC increased the abundance of gut microbiota such as Bacteroidota, Oscillospiraceae, Muribaculaceae, and Desulfovibrionaceae, as well as the concentrations of acetate acid, propionate acid, and butyrate acid in the feces. PC also activated short-chain fatty acid receptors, such as G-protein coupled receptor 43 in the colon, which promoted the proliferation of Treg cells. The depletion of gut microbiota and subsequent transplantation of fecal microbiota demonstrated that PC's effects on gut microbiota were effective in improving UC and restoring intestinal Th17/Treg homeostasis in a microbiota-dependent manner. This suggests that PC could be a promising functional food for the prevention and treatment of UC in the future.

Craft Beer Produced by Immobilized Yeast Cells with the Addition of Grape Pomace Seed Powder: Physico-Chemical Characterization and Antioxidant Properties.

The aim of this study was to produce and to characterize craft beer fermented by immobilized yeast cells with the addition of Prokupac grape pomace seed powder (2.5% and 5%), to obtain a beer enriched with phenolic compounds and improved sensory characteristics. The immobilization of the yeast cells was performed by electrostatic extrusion, while the obtained calcium alginate beads were characterized by light and scanning electron microscopy. Phenolic and hop-derived bitter compounds in beer with or without grape pomace seed powder (GS) phenolics were identified using UHPLC Q-ToF MS. The results indicated that GS adjunct significantly shortened the fermentation process of wort and increased the content of phenolic compounds, especially ellagic acid, flavan-3-ols and pro(antho)cyanidins in the final products compared to the control beer. A total of twenty (iso)-α-acids and one prenylflavonoid were identified, although their levels were significantly lower in beers with GS phenolics compared to the control beer. Beers with GS phenolics showed good antioxidant properties as measured by the reduction of ferric ions (FRP) and the scavenging of ABTS•+ and DPPH• radicals. The concentration of immobilized viable yeast cells was higher than 1 × 108 CFU/g wet mass after each fermentation without destroying the beads, indicating that they can be reused for the repeated fermentation of wort. Beers produced with 5% GS added to the wort exhibited the best sensory properties (acidity, astringency, bitterness intensity, mouthfeel, aftertaste and taste), and highest overall acceptability by the panelists. The results showed that grape pomace seed powder present a promising adjunct for the production of innovative craft beer with good sensory properties and improved functionality.

Tilapia gelatin films by incorporating metal-polyphenol network formed by procyanidin and zinc ion for pork preservation

There is a lack of information about the application of metal polyphenol networks (MPN) in the food industry nowadays. Herein, the MPN was prepared by procyanidin (PC) and zinc ion (Zn2+), and introduced into tilapia gelatin films. The MPN-modified films showed broader thickness, higher UV-Vis light barrier property, and lower water sensitivity and water vapor property than PC-modified films. When the molar ratio of Zn2+ to PC being 3:8, the incorporation of MPN induced the highest tensile strength of films reaching 82.47 MPa, good activity against oxidation, and improved inhibition activity to Staphylococcus aureus and Escherichia coli. The MPN-modified gelatin films could suppress the bacteria growth, and attenuate the generation of total volatile basic nitrogen and thiobarbituric acid reactive substances, causing the shelf life of pork extended by five and three days compared with the control and PC-modified films, respectively. The results suggested that MPN provided great potential in the application of food packaging.

Controlled delivery of procyanidin through magnesium oxide nanoparticles (MgO NPs) to improve the activity and mineralization of osteoblasts under oxidative stress in vitro

Excessive reactive oxygen species (ROS) in the microenvironment of osteoporosis (OP) not only accelerate the bone absorption, but also affect the osteogenic and mineralized effect of osteoblasts. Procyanidins (PC) have been reported to have anti-oxidation effects, but low bioavailability. This study aimed to explore the effect of magnesium oxide nanoparticles (MgO-PC NPs)-loaded PC on the osteogenesis and mineralization of osteoblasts that stimulated by H2O2. PC was loaded onto MgO NPs and characterized by transmission electron microscopy, energy dispersive spectroscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. After primary screening by cytotoxicity assay, MgO-PC NPs containing 20 μM of PC were chosen for further studies. In H2O2-stimulated osteoblasts, dichlorodihydrofluorescein diacetate probe, Cell Counting Kit-8, quantitative real-time polymerase chain reaction, alkaline phosphatase staining/activity and Alizarin red staining were used to detect the ROS production, cell viability and osteogenic and mineralized markers of osteoblasts. PC was loaded onto MgO NPs to successfully receive MgO-PC NPs with a diameter of about 144 nm and negative potential. PC can sustain release from MgO-PC NPs for at least 16 d. The controlled release of PC from MgO-PC NPs can effectively eliminate ROS and thereby promoted the cell activity. Most importantly, the osteogenesis and mineralization of osteoblasts under oxidative stress were also significantly reversed by MgO-PC NPS. Thus, these findings indicate that MgO-PC NPs may be developed as a potential therapeutic strategy for OP.

Oxidative Evolution of Different Model Rosé Wines Affected by Distinct Anthocyanin and Tannin Contents

The quality of rosé wines significantly depends on their phenolic composition, particularly tannins, anthocyanins, and their derivatives, which determine the perceived color of these products and their color evolution throughout the storage and shelf-life periods. This study investigated the impact of phenolic content on the oxidation and color evolution of five different model rosé wines obtained by blending a fixed amount of grape tannins with varying concentrations of oenocyanin to modulate their respective ratio and color intensity. The solutions were monitored for color and pigment changes promoted by oxidation in a Fenton-like environment. The findings revealed a potential correlation between the initial phenolic concentration and the different degrees of oxidation within each solution, resulting in significant variations in CIELAB data. Overall, all solutions exhibited a substantial decrease in redness, with losses ranging from 23% in the darkest solution to 43% in the lightest one compared to their initial levels. Additionally, their color profiles shifted toward yellow hues, up to triple the original value, indicating the degradation of the pigments responsible for the characteristic rosé color. Greater amounts of anthocyanins preserved higher Fe(II) concentrations over time, suggesting the antioxidant role of these compounds. The whole dataset also permitted the evaluation of the different oxidation susceptibilities of individual anthocyanins, among which derived pigments, such as vitisins, proved to be notably more stable than native pigments, particularly delphinidin and petunidin.

Rapid Detection of Tannin Content in Wine Grapes Using Hyperspectral Technology.

Wine grape quality is influenced by the variety and growing environment, and the quality of the grapes has a significant impact on the quality of the wine. Tannins are a crucial indicator of wine grape quality, and, therefore, rapid and non-destructive methods for detecting tannin content are necessary. This study collected spectral data of Pinot Noir and Chardonnay using a geophysical spectrometer, with a focus on the 500-1800 nm spectrum. The spectra were preprocessed using Savitzky-Golay (SG), first-order differential (1D), standard normal transform (SNV), and their respective combinations. Characteristic bands were extracted through correlation analysis (PCC). Models such as partial least squares (PLS), support vector machine (SVM), random forest (RF), and one-dimensional neural network (1DCNN) were used to model tannin content. The study found that preprocessing the raw spectra improved the models' predictive capacity. The SVM-RF model was the most effective in predicting grape tannin content, with a test set R2 of 0.78, an RMSE of 0.31, and an RE of 10.71%. These results provide a theoretical basis for non-destructive testing of wine grape tannin content.

Characterization of crude extracts from willow barks and their performance as proanthocyanidin -based coagulants in water treatment

This work investigates the proanthocyanidin profile of willow bark crude extracts and these materials were cationized and preliminarily tested as biocoagulants for water treatment. The characteristics of crude extracts proanthocyanidin were investigated using size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). XPS analysis indicates that the crude extracts contain significant amounts of sugars. Furthermore, SEC and liquid-state NMR spectroscopy showed that crude extract contains roughly 3–4 flavan-3-ol units with procyanidin (PC)/ prodelphinidin (PD) ratio of roughly 3–5. Thus, the modified form of tannin (proanthocyanidin-enriched) coagulants obtained the higher cationic charge density. The coagulation experiments with kaolin-river water mixture suggested that all the selected willow hybrids’ tannin coagulants were effective in settling the particles down. This study indicates that the value of willow bark can be significantly improved by the usage of crude extracts for water treatment.

Design and preparation of novel antioxidant and antibacterial films containing procyanidins and phycocyanin for food packaging.

The purpose of this study was to design a novel antioxidant and antibacterial film for food packaging using food-grade raw materials. The films were designed and fabricated based on carboxymethyl chitosan and pectin incorporated with procyanidins (PCs) and phycocyanin (Phy) by the tape casting method. The effects of different proportions of PCs and Phy on the properties and functions of the prepared films were studied. The results showed that the thickness of films could range from 55 to 70 μm, with dense network structure and uniform distribution of elements. Compared with C-Film group, the film loaded with PCs and Phy had lower water solubility and swelling rate, and higher tensile strength and elongation at break. FITR and XRD spectra revealed the molecular interaction mechanism among carboxymethyl chitosan, pectin, PCs and Phy, which could effectively endow the films with ultraviolet barrier properties. Moreover, the addition of PCs and Phy could effectively improve the antioxidant capacity and antibacterial effect of films, for example, the free radical scavenging abilities of most films were above 80% when the concentration of PCs was 40 μg mL-1. In view of these functional properties, the prepared film containing PCs and Phy have been successfully used in food packaging, which was proved by the preservation experiment of grapes. This study can provide theoretical and technical guidance for the preparation of biodegradable antibacterial films, and their application in the food packaging field.

Optimization of the extraction procedure of polyphenols from red Pinot Noir grape seeds

Grape seed extract (GSE) in the last years is commercialized as a valuable ingredient in the food industry. The aims of this study are to optimize the extraction procedure of polyphenols from seeds of red Pinot Noir grape and to evaluate the phenolic content, antioxidant and antimicrobial potential of the obtained extract. Two conventional methods (with shaker and magnetic stirrer) and two non-conventional methods (with ultrasonic bath and microwave oven) were used for the extraction of the polyphenols from seeds. The optimal conditions for the production of GSE were - magnetic stirrer, 70% aqueous ethanol, 3 h, room temperature. The extraction yield and total phenol content of the obtained extract were 12% and 111.22 mg gallic acid/g dry weight, respectively. The contents of total flavonoids (TF), procyanidins (PC), total anthocyanins and ascorbic acid of the GSE were determined. The obtained GSE was rich in TF (51.50 mg quercetin/g) and PC (170.45 mg catechin/g). Antioxidant capacities of the extract were evaluated by 2,2-diphenyl-1-picrylhydrazyl (579.33 μM Trolox/g) and 2,2′-azino-bis (3ethylbenzothiazoline-6-sulfonic acid) assays (2203.50 μM Trolox/g). The extract has a high antimicrobial effect against B. cereus and B. subtilis. The obtained Pinot Noir GSE will be suitable additive for food products.

Preparation and characterisation of wheat starch-based aerogels for procyanidin encapsulation to enhance stability

Procyanidins (PC) are formed by the polymerisation of flavan-3-ol monomers, which have excellent bioactivity and present great health benefits.

Red Wine Inspired Chemistry: Hemisynthesis of Procyanidin Analogs and Determination of Their Protein Precipitation Capacity, Octanol-Water Partition, and Stability in Phosphate-Buffered Saline.

Ten dimeric procyanidin (PC) analogs were hemisynthesized from catechin or epicatechin and from five different aldehydes using the same mechanism that produces the important acetaldehyde-mediated adducts of proanthocyanidins (PAs) and anthocyanins in red wine. Protein precipitation capacity (PPC), octanol-water partition coefficient (log P) and stability of the PC analogs were determined. The emphasis was on the PPC because it has been shown to correlate with anthelmintic activity against gastrointestinal nematodes in ruminants and with other beneficial bioactivities in animals, as well. The PPC of PC analogs was greatly improved compared to natural PC dimers, but the capacity was not as great as that of a PC trimer or epigallocatechin gallate. The log P of PC analogs varied from hydrophobic to hydrophilic depending on the intramolecular linkage. Great variation was observed in stabilities of PC analogs in phosphate buffered saline, and the mixtures of degradation products were characterized using high-resolution mass spectrometry.

Bassia longifolia (= Madhuca longifolia): Isolation of flavan-3-ols and their contribution to the antibacterial and antidiabetic activity in vitro

Bassia longifoliaKOENIG (= Madhuca longifolia (L.) is an evergreen tree that is widely distributed throughout Nepal, India, and Sri Lanka. The bark has various traditional uses: as a paste in the treatment of cuts and wounds or internally as a decoction that is given to diabetic patients. Chemical-analytical and pharmacological investigations regarding the bark are not sufficiently available. We focused on the isolation of flavan-3-ols from the methanolic extract and their contribution to the described traditional uses in wound healing and diabetes treatment. Therefore, an antibacterial assay and an α-glucosidase assay were performed. The isolation process was performed by a combination of Sephadex®-, MCI®-Gel-, and RP-18 chromatography. The structures of the isolated compounds were elucidated by 1H- and 13C-NMR-spectroscopy including COSY, ROESY, HSQC, and HMBC methods. Optical characterization was performed by polarimetry and circular dichroism. Two monomeric, seven dimeric, six trimeric, and one tetrameric flavan-3-ols were found including one dimer and three trimers with rare epiafzelechin units. Two compounds were isolated for the first time. A fraction containing higher oligomeric and polymeric proanthocyanidins (PAs) was examined by 13C NMR spectroscopy and revealed an average degree of polymerization of 8–9. PA with cis-configurated subunits predominated at 90 % and the presence of further monohydroxylated flavan-3-ols was revealed. Minimal inhibitory concentrations (MICs) were investigated by the serial microdilution broth assay with Staphylococcus aureus. The bacterial suspension was inoculated on agar plates for determining the MICs. The α-glucosidase assay was performed in 96 well plates with α-glucosidase from Bacillus stearothermophilus. For the detection of enzyme inhibition, p-nitrophenyl-α-d-glucopyranoside was used as a substrate and after incubation absorbance was measured at 405 nm. Antibacterial effects were only found for fractions enriched with PAs or containing higher oligomeric and polymeric flavan-3-ols. All tested substances showed high α-glucosidase inhibition. Whereby 4β→8 conjugated dimers and the monomers showed the lowest inhibition, procyanidin (PC) B5 as 4β→6 conjugated and cinnamtannin A2 as tetrameric flavan-3-ol showed the highest. PAs with epiafzelechin units are rarely found in nature but their reoccurring appearance in B. longifolia could be characteristic of this plant. For its traditional uses, the antibacterial activity of the PA-enriched fractions could contribute to the wound healing process when applied to the injured skin. Moreover, all tested substances and fractions showed α-glucosidase inhibition, which could also explain the use of a decoction in the treatment of diabetes. In conclusion, pharmacological investigations could provide scientific evidence for traditional uses of B. longifolia.

Targeted metabolomics reveals key phenolic changes in pecan nut quality deterioration under different storage conditions.

Pecan nuts are highly enriched in phenolic compounds, which contribute to the health benefits of pecans. Phenolic compounds represent the main oxidation reaction substrates, thus leading to quality deterioration, namely pellicle browning or a decrease in beneficial effects during pecan storage. Hence, four different storage conditions were performed for 180 d to simulate real production situations. Targeted metabolomics was chosen to identify the specific phenolic compounds involved in quality deterioration under different storage conditions in 0, 90, and 180 d samples. A total of 118 phenolic compounds were detected, nine of which were identified for the first time in pecan. The total phenolic content (TPC) and antioxidant capacities initially demonstrated high scores, after which they tended to decrease during the storage process. The significantly modified phenolic compounds during storage were selected as the metabolite markers of pecan quality deterioration, including catechin, procyanidin (PA) trimer, PA tetramer, trigalloyl hexahydroxydiphenoyl (HHDP) glucose, and tetragalloyl hexoside. Fresh pecan kernels resulted in more pronounced changes in hydrolysable tannins (HTs), whereas dry kernels resulted in the most accentuated changes in condensed tannins (CTs). To the best of our knowledge, this is the first attempt to study individual phenolic changes during storage of pecan in such massive amounts. The results can offer a valuable theoretical basis for future control of pecan quality deterioration through phenolics during storage.

Size-controllable food-grade nanoparticles based on sea cucumber polypeptide with good anti-oxidative capacity to prolong lifespan in tumor-bearing mice

Liver cancer, a malignancy with a rising global incidence, poses a significant challenge in achieving effective treatment outcomes. As food-derived nutrient, sea cucumber peptide (SCP) has shown promising anticancer effects. Therefore, we explored the nanodelivery systems to encapsulate SCP to enhance its stability in the gastrointestinal tract and improve absorption within the tumor microenvironment. This study aimed to develop size-controllable multifunctional nanoparticles using SCP, procyanidins (PCs), and vanillin through molecular assembly via a one-pot Mannich condensation approach. These food-grade nanoparticles demonstrated water solubility and exhibited a spherical structure with sizes ranging from 441 to 1360 nm, depending on the concentration of the reactants. In vitro cell experiments demonstrated that SCP nanoparticles modified with PCs effectively reduced the generation of reactive oxygen species from H2O2 and acrylamide while maintaining normal levels of mitochondrial membrane potential. Furthermore, in vivo nutrition intervention studies conducted on tumor-bearing mice revealed that mice treated with SCP nanoparticles exhibited a survival rate of 40 %, which was significantly higher than the 0 % and 20 % survival rates observed in the control and SCP-treated groups, respectively. These findings suggest that SCP nanoparticles, possessing antioxidative properties and controllable sizes, hold potential for precision nutrition in the field of cancer treatment.

Procyanidins: A promising anti-diabetic agent with potential benefits on glucose metabolism and diabetes complications.

Diabetes mellitus (DM) is a complex disease with alarming worldwide health implications and high mortality rates, largely due to its complications such as cardiovascular disease, nephropathy, neuropathy, and retinopathy. Recent research has shown that procyanidins (PC), a type of flavonoid, have strong antioxidant and free radical elimination effects, and may be useful in improving glucose metabolism, enhancing pancreatic islet cell activity, and decreasing the prevalence of DM complications. This review article presents a systematic search for peer-reviewed articles on the use of PC in the treatment of DM, without any language restrictions. The article also discusses the potential for PC to sensitise DM medications and improve their efficacy. Recent in vivo and in vitro studies have demonstrated promising results in improving the biological activity and bioavailability of PC for the treatment of DM. The article concludes by highlighting the potential for novel materials and targeted drug delivery methods to enhance the pharmacokinetics and bioactivity of PC, leading to the creation of safer and more effective anti-DM medications in the future.

Fabrication and performance evaluation of PLCL-hCOLIII small-diameter vascular grafts crosslinked with procyanidins

Cardiovascular disease has become one of the main causes of death. It is the common goal of researchers worldwide to develop small-diameter vascular grafts to meet clinical needs. Collagen is a valuable biomaterial that has been used in the preparation of vascular grafts and has shown good results. Recombinant humanized collagen (RHC) has the advantages of clear chemical structure, batch stability, no virus hazard and low immunogenicity compared with animal-derived collagen, which can be developed as vascular materials. In this study, Poly (l-lactide- ε-caprolactone) with l-lactide/ε-caprolactone (PLCL) and type III recombinant humanized collagen (hCOLIII) were selected as raw materials to prepare vascular grafts, which were prepared by the same-nozzle electrospinning apparatus. Meanwhile, procyanidin (PC), a plant polyphenol, was used to cross-link the vascular grafts. The physicochemical properties and biocompatibility of the fabricated vascular grafts were investigated by comparing with glutaraldehyde (GA) crosslinked vascular grafts and pure PLCL grafts. Finally, the performance of PC cross-linked PLCL-hCOLIII vascular grafts were evaluated by rabbit carotid artery transplantation model. The results indicate that the artificial vascular grafts have good cell compatibility, blood compatibility, and anti-calcification performance, and can remain unobstructed after 30 days carotid artery transplantation in rabbits. The grafts also showed inhibitory effects on the proliferation of SMCs and intimal hyperplasia, demonstrating its excellent performance as small diameter vascular grafts.

The combined anticancer of peanut skin procyanidins and resveratrol to CACO-2 colorectal cancer cells.

Colorectal cancer is one of the leading causes of cancer deaths worldwide. Currently, chemotherapy is the primary way for colorectal cancer, but with severe side effects. Therefore, it is urgent to find safer and more effective adjuvant treatment methods. At present, natural active substances are promising alternatives, as numerous studies have demonstrated possible synergistic anticancer effects in plant-active polyphenols. In the present study, the combined effect of procyanidins (PC) (from peanut skin) and resveratrol (RES) (from peanut buds) on the synergistic anticancer potential was investigated. CACO-2 and HCT-8 cells were served as colorectal cancer models, and HEPG-2 and HUH-7 cells were served as liver cancer models to observe the effects of PC and RES alone or in combination on the growth and proliferation of these four types of cancer cells. The results revealed that both PC and RES could inhibit the cells' proliferation in a manner with concentration-dependent, but they exerted synergistic anticancer effects only on CACO-2 cells. PC and RES could synergistically inhibit CACO-2 cell clone formation, inducing apoptosis of CACO-2 cells and blocking their cell cycle in G0/G1 phase. Additionally, as observed by the results of Western blot assay, the combined effect of PC and RES also inhibited the phosphorylation of Thr308, Ser473, and ERK and promoted the phosphorylation of IKBα and NF-κB in CACO-2 cells. These findings collectively indicate that PC combined with RES might exert synergistic anticancer effects by regulating AKT, ERK, and NF-κB signaling pathways.

Subtle distinction in molecular structure of flavonoids leads to vastly different coating efficiency and mechanism of metal-polyphenol networks with excellent antioxidant activities

Metal-polyphenol networks (MPNs) are of immense scientific interest because of their simple and rapid process to deposit on various substrates or particles with different shapes. However, there are rare reports on the effect of polyphenol molecular structure on coating efficiency and mechanism of MPNs. Herein, three typical flavonoid polyphenols, catechin (Cat), epigallocatechin (EGC) and procyanidin (PC), with the same skeleton (C6-C3-C6) but subtle distinction in molecular structure, were selected to build MPN coatings with ferric ions (Fe3+). And various techniques combined with the density functional theory (DFT) were applied to deeply reveal the roles of coordinative phenolic hydroxyl groups as well as noncovalent interactions (hydrogen bonding and π − π stacking) in the formation of flavonoid-based MPNs. We found that more accessible numbers of coordinative phenolic hydroxyl groups, the higher coating efficiency. In these flavonoid-based MPNs, the single-complex is the predominant during the coordinative modes between phenolic hydroxyl and Fe3+, not the previously reported mono-complex, bis-complex and/or tris-complex. Besides coordinative interaction, noncovalent interactions also contribute to MPNs formation, and hydrogen bonds prevail in the noncovalent interaction compared with π-π stacking. And these engineered MPN coatings can endow the substrate with excellent antioxidant activities. This study contributes to in-depth understanding the building mechanism of flavonoid-based MPNs, and increasing coating efficiency by choosing proper polyphenols.