Epigallocatechin Research Articles

PCL/Fucoidan nanofiber membrane loaded HP-β-CD/EGC inclusion complexes for food packaging based on self-assembly strategy

In this study, 2-Hydroxypropyl-β-cyclodextrin (HP-β-CD)/Epigallocatechin (EGC) inclusion complexes were prepared by ultrasound-guided, and Polycaprolactone (PCL)/Fucoidan (FD) nanofiber membranes were rapidly prepared by electrospinning technology. The test results showed that the average diameter of the nanofiber film increased from 1429.11 to 1728.12 nm, the water vapor permeability was enhanced, the crystallinity was reduced, and the surface was hydrophilic. Infrared spectroscopy and thermal analysis showed that hydrogen bonds were formed between the inclusion complexes and PCL/FD nanofibrous membranes, which improved the thermal stability of the fibrous membrane. The membrane exhibited the sustained release characteristics of EGC within 240 h and exhibited excellent antibacterial properties in vitro and in vivo. These results indicated that the developed nanofibrous membranes have promising applications in food packaging.

Efficient enzymatic synthesis of theaflavin and its production mechanism.

In this study, a novel preparation method of theaflavin (TF) has been established. Our findings indicated that the formation of TF was significantly enhanced by using an ice bath (2-3°C). Additionally, increasing the ratio of (-)-epigallocatechin (EGC) under the ice bath could further improve its yield. This approach prevented the appearance of a dark solution within 3h, effectively protecting TF from oxidation. Our study on the generation mechanism of TF suggested that EGC-quinone I (EGC-Q-I) with two carbanions could potentially serve as one of synthons based on the retrosynthetic analysis of the bicyclo[3.2.1]octane-type intermediate. Subsequently, quantum mechanical calculations further supported this hypothesis. Practical Application: In this study, we have developed a novel method for the synthesis of theaflavin (TF), demonstrating that the use of ice bath significantly enhanced its yield. Increasing the ratio of (-)-epigallocatechin (EGC) under the ice bath further improved TF yields and prevented darkening of the solution for at least 3h, thereby protecting TF from oxidation. Our study suggested that EGC-quinone I is a potential synthon based on the retrosynthetic analysis of the bicyclo[3.2.1]octane-type intermediate (BOI). This hypothesis is supported by QM calculations.

Green tea extracts and substantial catechin derivatives: Evaluation of their potential against breast cancer

Breast cancer is one of the most predominant types of cancer. Although assorted treatment options are available to cope with breast cancer (e.g. chemotherapy, radiotherapy, surgery, hormone therapy, targeted therapy), chemotherapy regimens still hold vital importance. Studies on the discovery of drug-candidate molecules that can create an alternative in the treatment of breast cancer continue at full speed. At this point, nature has a substantial place offering great diversity. Natural products may exhibit anticancer properties directly through molecular targets such as genes or indirectly through metabolic pathways. Moreover, they may be adjuvant agents and contribute to conventional therapy, and thus, they can enhance the efficacy of chemotherapeutics or even ease their side effects. Green tea, a critical dietary source of polyphenols and flavonoids, is obtained from the minimally fermented or unfermented leaves of the Camellia sinensis L. plant and is used in traditional Chinese medicine for many important conditions, including cancer. The phytochemical content of green tea is extremely rich, including (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC); (-)-epicatechin-3-gallate (ECG) and (-)-epicatechin (EC) as the main catechins in the composition of green tea. Within the scope of our study, we proposed the cytotoxicity and toxicity comparison of the water and 80% ethanolic extract of the green tea extracts as well as of (-)-epicatechin (EC) and (-)-epigallocatechin (EGC) in terms of their cytotoxicity and toxicity based on the structure-activity relationship on breast cancer. Therefore, we tested aqueous and 80% ethanolic extracts of green tea and EGC and EC on MDA-MB-231, MDA-BMB-468, MCF-7 and SK-BR-3 breast cancer cells. Their toxicity on healthy rat myoblastoma H9c2 cells was further examined. Resazurin reduction assay was used to detect cytotoxicity and toxicity. Both water and 80% ethanolic extract of green tea exhibited remarkable cytotoxicity on MCF-7 cancer cells deserving further investigation, including phytochemical characterization of the extract. Epigallocatechin was also cytotoxic on MCF-7 cells with an IC50 value of 20.07 µM. The possible therapeutic potentials of green tea extracts and their substantial catechin derivatives were assessed for breast cancer therapy.

The SAR analysis of dietary polyphenols and their antagonistic effects on bortezomib at physiological concentrations.

Background: Bortezomib (BTZ), a primary treatment for MM, but its effectiveness can be reduced by interactions with vicinal diol moieties (VDMs) in polyphenols. Despite this, it's debated whether BTZ therapy necessitates avoiding polyphenol-rich products, given the low bioavailability of polyphenols. Additionally, it remains unclear whether the structure of polyphenols contributes to their BTZ antagonism. Therefore, our study aims to unravel the structure-activity relationship of dietary polyphenols and their BTZ antagonism at daily diet-achievable physiological concentrations. Methods: We assessed the antagonistic effects of 25 polyphenols against BTZ using cell viability assays in RPMI 8226 cells. ChemGPS-NP helped analyze the structural similarity. Additionally, long-term cytotoxicity assays evaluated these effects at physiologically relevant concentrations. Results: By cell viability assays, we found a positive correlation between the number of VDMs in gallotannins and their BTZ antagonism. Moreover, the origin and configuration of VDMs, rather than the total VDM concentration, play a pivotal role in the combined antagonistic effects against BTZ in gallotannins. Additionally, ChemGPS-NP analysis indicated that the aromaticity and C-3 hydroxyl group in flavonoids' C-rings enhance their BTZ antagonism. Finally, long-term cytotoxicity assays reveal that gallic acid (GA), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), at their physiological concentrations-attainable through tea consumption-significantly and synergistically antagonize BTZ. Conclusion: Due to the potential for these polyphenols to reduce the effectiveness of BTZ, it is advisable for MM patients undergoing BTZ treatment to reduce their consumption of foods high in VDM-containing polyphenols.

Tea polyphenol EGC suppresses colorectal cancer cell proliferation both in vitro and in vivo via downregulation of STAT3

Epigallocatechin (EGC) is one of the main bioactive polyphenols in green tea. This study aims to determine the anti-tumor effect of EGC against colorectal cancer. Our results revealed that treatment of EGC led to significant suppression of cell proliferation and apoptosis in three colorectal cancer cells. Western blot confirmed that EGC activated Caspase-3 and PARP, down-regulated the phosphorylation of STAT3 and decreased Bcl-2 expression. Luciferase-reporter-activity assay further determined that EGC suppressed the promoter activity of STAT3 and downregulated the transcription of STAT3. Besides, in vivo study proved that EGC (100 mg/kg) resulted in significant suppression of tumor volume and tumor weight (decreased by 63.7 %) in mice bearing SW620 tumors. Tumor organoid assays demonstrated the inhibitory efficacy of EGC in colorectal organoids. In conclusion, our study present evidence that EGC inhibited colon cancer cell proliferation both in vitro and in vivo by down-regulation phosphorylated STAT3 and activated downstreams.

Comprehensive analysis of fresh tea (Camellia sinensis cv. Lingtou Dancong) leaf quality under different nitrogen fertilization regimes

Our study investigated the impact of nitrogen fertilization at 0, 150, 300, and 450 kg/ha on the non-volatile and volatile substances, as well as gene expression in fresh leaves from Lingtou tea plants. We found that applying nitrogen at 450 kg/ha notably increased total polyphenols (TPs) and free amino acids (AAs) while decreasing the TP to AA ratio (TP/AA) and total catechins (TC) contents. Chlorophyll, caffeine (CAF) and theanine accumulated to a greater extent with nitrogen application rates of 150, 300, and 450 kg/ha, respectively, six substances – TP, CAF, TC, theanine, epigallocatechin (EGC), and AA – as key contributors to the taste quality of LTDC. Additionally, five substances with variable importance in projections (VIP) ≥ 1 and odor activation values (OAV) ≥ 1, notably linalool and cis-linalool oxide (furanoid), significantly contributed to the tea's overall aroma. Furthermore, applying 300 kg/ha nitrogen upregulated the dihydroflavonol reductase (DFR)gene, likely causing catechin decrease.

Exploring the potential of deep eutectic solvents for extracting bioactive compounds from tea: Insights from molecular dynamics simulations

Deep eutectic solvents (DESs) are sustainable alternatives to traditional solvents used for natural compound extraction. In this study, the possibility of extracting alkaloids, flavonoids, and catechin compounds from tea plants is investigated using four different binary eutectic solvents through molecular dynamics (MD) simulations and Density functional theory (DFT) calculations. The structural and thermodynamic characteristics of the solvents, as well as their interactions with the tea's bioactive components, are explored. In this study, choline chloride (CHO) is combined with 1,2-butanediol (1,2BUT), 1,3-butanediol (1,3BUT), 1,4-butanediol (1,4BUT), and 2,3-butanediol (2,3BUT) to produce four different types of solvents. According to the obtained results from the MD simulation, the interaction of the target compounds with the different DESs varied significantly, some of the solvents are more soluble and show a good selectivity for certain compounds. The average total interaction energy of target molecules with the solvents follows the order Epigallocatechin (EGC) > Epicatechin gallate (ECG) > Epigallocatechin gallate (EGCg) > Kaempferol (KAM) > Theobromine (TBM) > Caffeine (CAF) > Catchin (CAT). Therefore, among the target molecules, EGC interacts more effectively with solvents. The interaction energy of this molecule with the solvent is changed from −24 kJ/mol to −95 kJ/mol. Overall; this study highlights the importance of considering the specific target compounds when selecting a binary eutectic solvent for extraction and provides a theoretical basis for further experimental investigations.

Green Tea Catechins as Potential Drug Scaffolding Molecules in Structural Studies with Diverse Protein Targets

Abstract: Previous studies provide substantial evidence that catechins, polyphenol bioactive compounds, exhibit medicinal benefits. These polyphenols are found in abundance in green teas, including a combination of the four major types of catechins: (-)-Epicatechin (EC), (-)-Epicatechin-3-gallate (ECG), (-)- Epigallocatechin (EGC), and (-)- Epigallocatechin-3-gallate (EGCG). Although all four exhibit medicinal benefits, the catechin cited in the literature the most is EGCG, so derivatives of this catechin were selected for these studies. Literature searches identified catechins as biologically active compounds for a diverse set of diseases ranging from cancer, metabolism, neurological, and neuromuscular ailments. A diverse set of potential protein targets for docking with catechin derivatives was first identified as a list (n = 48). The targets were then selected based on the presence of 3D protein coordinates for these targets provided by the Rutgers Consortium for Structural Biology (RCSB) Protein Data Bank (PDB) (n = 10). The surfaces of the 3D protein targets were evaluated with computational methods to identify potential binding sites for the EGCG catechin derivatives. Static and flexible docking was done using target protein binding sites performed with the catechin derivatives followed by molecular dynamics (MD). MD protocols were run to confirm binding in the physiological range and environment. In summary, the results of computational protocols confirmed predicted binding by docking with MD of several catechin derivatives to be used as scaffolds once validated in lab-based assays. Possible changes to these scaffolding molecules that could result in tighter, more specific binding is discussed.

Genome-Wide Association Studies of Biluochun Tea Plant Populations in Dongting Mountain and Comprehensive Identification of Candidate Genes Associated with Core Agronomic Traits by Four Analysis Models.

The elite germplasm resources are key to the beautiful appearance and pleasant flavor of Biluochun tea. We collected and measured the agronomic traits of 95 tea plants to reveal the trait diversity and breeding value of Biluochun tea plant populations. The results revealed that the agronomic traits of Biluochun tea plant populations were diverse and had high breeding value. Additionally, we resequenced these tea plant populations to reveal genetic diversity, population structure, and selection pressure. The Biluochun tea plant populations contained two groups and were least affected by natural selection based on the results of population structure and selection pressure. More importantly, four non-synonymous single nucleotide polymorphisms (nsSNPs) and candidate genes associated with (-)-gallocatechin gallate (GCG), (-)-gallocatechin (GC), and caffeine (CAF) were detected using at least two GWAS models. The results will promote the development and application of molecular markers and the utilization of elite germplasm from Biluochun populations.

Novel Oxidation Oligomer of Chlorogenic Acid and (-)-Epigallocatechin and Its Quantitative Analysis during the Processing of Keemun Black Tea.

Not only do flavan-3-ols participate in the formation of chromogenic oxidation products such as theaflavins, but chlorogenic acid (3-caffeoylquinic acid, CQA) is also involved in the enzymatic oxidation during black tea processing. The critical oxidation product of CQA and (-)-epigallocatechin (EGC) were identified as an adduct containing benzobicyclo[3.2.2]nonenone structure, which was named as the dichlorogeniccatechin (DCGC) oligomer. It was composed of two molecules of CQA and one molecule of EGC. The effects of the initial reactant ratio and reaction time on the generation of DCGC were also analyzed. A high proportion of CQA promoted the production of DCGC, but a high proportion of EGC inhibited the DCGC formation. In addition, the content of DCGC in Keemun black tea during processing was determined. The content of DCGC highly increased after withering but decreased after drying. This study provides a new perspective for the investigation of other oxidation oligomers in black tea.

The Analysis and Rapid Non-Destructive Evaluation of Yongchuan Xiuya Quality Based on NIRS Combined with Machine Learning Methods

This paper attempts to analyze and assess Yongchuan Xiuya tea quality quickly, accurately, and digitally. The sensory evaluation method was first used to assess Yongchuan Xiuya tea quality, and then near infrared spectroscopy (NIRS) was obtained, and standard methods were applied to the testing of the chemical components. Next, principal component analysis (PCA) and the correlation coefficient method were used to comprehensively screen out the representative components. Finally, NIRS combined with partial least squares regression (PLSR) and back propagation artificial neural network (BP-ANN) methods were applied to build quality evaluation models for Yongchuan Xiuya tea, respectively, and external samples were employed to examine the practical application results of the best model. The cumulative variance contribution rate of the first three principal components of the ingredients in tea was 97.73%. Seven components closely related to tea quality were screened out, namely, amino acids, total catechin, epigallocatechin gallate (EGCG), tea polyphenols, water extracts, epicatechin gallate (ECG), and epigallocatechin (EGC) (p < 0.01). Between the two models established to predict the tea quality, the model built by the PLS method had the better results, whose coefficient of determination of prediction (Rp2) and root mean square error of prediction (RMSEP) were 0.7955 and 1.2263, respectively, and the best results were obtained by the nonlinear BP-ANN model, whose Rp2 and RMSEP were 0.9315 and 0.6787, respectively. The 10 external Yongchuan Xiuya samples were employed to test the best BP-ANN model, and the results of R2 and RMSEP were 0.9579 and 0.6086, respectively, meaning that the model has good robustness. Therefore, the model established by NIRS combined with the BP-ANN method can be used to assess Yongchuan Xiuya tea quality rapidly, accurately, and digitally, and it can also provide new ideas and methods for evaluating the quality of other teas.

Gallation and B-Ring Dihydroxylation Increase Green Tea Catechin Residence Time in Plasma by Differentially Affecting Tissue-Specific Trafficking: Compartmental Model of Catechin Kinetics in Healthy Adults.

Catechins in green tea extract (GTE) (epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin (EC), epicatechin gallate (ECG)) vary in bioactivity. We developed a physiologically relevant mathematical model of catechin metabolism to test the hypothesis that fractional catabolic rates of catechins would be differentially affected by their structural attributes. Pharmacokinetic data of plasma and urine catechin concentrations were used from healthy adults (n = 19) who ingested confections containing 0.5 g GTE (290 mg EGCG, 87 mg EGC, 39 mg EC, 28 mg ECG). A 7-compartmental model of catechin metabolism comprised of the gastrointestinal tract (stomach, small and large intestine), liver, plasma, extravascular tissues, and kidneys was developed using a mean fraction dose of EGCG, ECG, EGC, and EC. Fitting was by iterative least squares regression analysis, and goodness of fit was ascertained by the estimated variability of parameters (FSD < 0.5). The interaction of gallation and B-ring dihydroxylation most greatly extended plasma residence time such that EGC > EC = EGCG > EGC. The interaction between gallation and B-ring dihydroxylation accelerated the transfer from the upper gastrointestinal tract to the small intestine but delayed subsequent transfers from the small intestine through the liver to plasma and from kidneys to urine. Gallation and B-ring dihydroxylation independently delayed the transfer from plasma to extravascular tissues, except the uptake to kidneys, which was slowed by gallation only. This multi-compartment model, to be validated in a future study, suggests that gallation and B-ring dihydroxylation affect catechin catabolism in a tissue-specific manner and thus their potential bioactivity.

Antioxidant Capacity of Black Tea Obtained Using Tyrosinase and Tannase Treatment

Black tea has a lower antioxidant capacity than other teas, such as green tea, white tea, and oolong tea. Tannase and tyrosinase can be used as a treatment to improve the quality of black tea infusion. Tannase has been reported to be an effective way to enhance antioxidant activity in black tea infusion. Meanwhile, tyrosinase could produce higher theaflavin content than thearubigin. Research about Ready-to-Drink (RTD) black tea preparation with the addition of tannase and tyrosinase to fresh tea leaves before pasteurization has not been reported. This study aimed to find a good combination of tannase (1 mg/ml) and tyrosinase (111; 446; 1785 U/ml) to produce high antioxidant activity of RTD black tea. The results showed that higher tyrosinase concentration decreased the antioxidant activity (DPPH and reducing power), epicatechin (EC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG) content yet increased the theaflavin content and theaflavin (TF)/thearubigin (TR) ratio in the tannase-tyrosinase treated black tea. Still, the highest concentration of tyrosinase (1785 U/ml) in tannase-tyrosinase black tea produces higher antioxidant activities, gallic acid, EC, and EGC content than commercial black tea and tyrosinase without tannase-treated black tea. Thus, the combination of tannase (1 mg/ml) and tyrosinase (1785 U/ml) could be the best treatment to produce high-antioxidant black tea.

Comparative Analysis of Bioactive Phenolic Compounds and Fatty Acids in Seeds and Seedlings of Canadian Alfalfa, Sainfoin, and Fenugreek

The interest in under-utilized crops as a functional food for animals and humans has been increasing recently with advancing research and the need for crop improvement. Canadian forage crops including alfalfa (Medicago sativa L.) and fenugreek (Trigonella foenum-graecum L.) are marketed in various forms due to their traditionally known health benefits. Sainfoin (Onobrychis viciifolia Scop.) is another forage crop with potential health benefits containing beneficial nutraceuticals. In this study, we assessed selected bioactive phenolic compounds and fatty acids in seeds and seedlings of Canadian-grown alfalfa, sainfoin, and fenugreek. Various phenolic compounds were detected in all three forage crop seeds and seedlings. In general, Sainfoin seeds were high in phenolic compounds relative to that of alfalfa and fenugreek. Chlorogenic acid, epigallo catechin, and gallic acid were at high concentrations at 56.6, 86.8, and 64.7 µg.g−1, respectively, compared to other phenolic compounds in sainfoin seeds. The fatty acids content (%) was significantly affected by the seedling stage and crop type. Some of the bioactive compounds present in seeds were not detected in seedling stages. The comparative bioactive phenolic compounds and fatty acid assessments of these forage legumes could potentially be used as biomarkers for the selection and development of favorable cultivars for animal and human nutrition. In addition, these crops could be used for isolating these bioactive compounds, and thus increasing their agri-food value.

Chemical and biological characteristics of Sri Lankan white tea

White tea is the rarest of all kinds of tea and has numerous health benefits. Sri Lankan white tea fetches the highest premium price on the market because of its distinct color and flavor. This is the first report on the chemical and biological activities of Sri Lankan white tea. This study evaluated the total polyphenol content, major catechins, including, (+)-catechin, (-)-epigallo catechin-3-gallate (EGCG), epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), and caffeine content of white tea collected from different elevations in Sri Lanka. The inhibitory effects of white tea on α-amylase, α-glucosidase, lipase, acetylcholine esterase, xanthine oxidase, and tyrosinase enzymes were evaluated. Ferric reducing antioxidant power (FRAP), DPPH, and ABTS radical scavenging activities were performed to determine the antioxidant capacity. The total polyphenol and catechin contents of white tea ranged from 18.21 % to 22.52 % and 5.32–12.22 %, respectively. White tea exhibited xanthine oxidase, acetylcholine esterase, and α-glucosidase inhibitory activity with the IC50 values in the range of 2.51–48.96, 14.2–54.21 and 6.38–33.14 ppm., respectively. Sri Lankan white tea has strong antioxidant activity as well as acetylcholine esterase, α-glucosidase, and xanthine oxidase inhibitory activities. In addition, white tea showed moderately inhibiting activities of lipase and tyrosinase.

Effects of Key Components on the Antioxidant Activity of Black Tea.

Many components (such as tea polyphenols, catechins, theaflavins, theasinensins, thearubigins, flavonoids, gallic acid, etc.) in black tea have antioxidant activities. However, it is not clear which components have a greater influence on the antioxidant activity of black tea. In this study, the antioxidant activity and contents of tea polyphenols, catechins, theaflavins, thearubigins, theabrownins, TSA, total flavonoids, amino acids, caffeine, and total soluble sugar were analyzed in 51 black teas. Principal component analysis (PCA), orthogonal partial least-squares discrimination analysis (OPLS-DA), and the correlation analysis method were used for data analysis. The results showed that catechins in tea polyphenols were the most important components that determine the antioxidant activity of black tea. Among them, epicatechin gallate (ECG), epi-gallocatechin gallate (EGCG), epicatechin (EC), and epi-gallocatechin (EGC) were significantly positively correlated with the antioxidant activity of black tea, and theabrownin was negatively correlated with the antioxidant activity of black tea. Furthermore, this study analyzed the correlation between the changes in catechin and its oxidized polymers with antioxidant activity during black tea fermentation; it verified that catechins were significantly positively correlated with the antioxidant activity of black tea, and theabrownin showed a negative correlation. And the antioxidant activity of catechins and their oxidation products in vitro and their correlation in black tea processing were used as validation. This study provides a comparison method for comparing the antioxidant activity of black tea.

Discriminating compounds identification based on the innovative sparse representation chemometrics to assess the quality of Maofeng tea

The rich flavors and antioxidant properties within Maofeng tea are mainly attributable to numerous secondary metabolites and thus may be related to quality. Motivated by this finding, our study presents a sparse representation (SR) scheme to analyze the content of various secondary metabolites and thus identify discriminating compounds (DCs) for the modelling of Maofeng tea quality. We first identified the DCs in terms of an interpretable sparse recovery strategy with LASSO regression. The optimal regularization term was estimated by a specific Karush–Kuhn–Tucker (KKT) optimal condition. Then, qualitative analysis models were trained with screened DCs and utilized to predict the quality of unseen Maofeng samples. For this purpose, 96 Maofeng samples of 6 different quality grades were collected, and standardized stoichiometry techniques determined 21 quality-related bioactive compounds and empirical quality indicators. The experimental results show that epigallocatechin (EGC), epicatechin (EC), gallocatechin gallate (GCG) and total catechins (TC) were identified as significant discriminating features, and the KNN algorithm provided the best assessment accuracy of 95.79%. Overall, the result demonstrates the superior performance of benchmarks for enhancing the reliable prediction of Maofeng tea quality, not only prediction accuracy but also providing interpretable assessment.

A combination of green tea polysaccharide conjugate and bovine serum albumin and its emulsion-stabilizing characteristics

Tea polysaccharide conjugates (TPC) and bovine serum albumin (BSA) have emulsifying properties, but they have certain shortcomings when used alone as emulsifiers. This study aimed to combine TPC and BSA to form a complex for applications to achieve the complementary advantages between them. The TPC/BSA complex was physicochemically characterized, and the results showed an improvement in its surface hydrophobicity. TPC/BSA emulsions with different concentrations (0.20–1.00 wt%) were prepared using TPC/BSA complex as the emulsifier. The effects of heat treatment, pH, and metal ions on the stability of TPC/BSA and BSA emulsions were investigated, and TPC/BSA emulsion systems loaded with epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were constructed. TPC/BSA emulsion droplets were smaller than 1.00 wt% TPC emulsion droplets, and the particle size of 0.20 wt% TPC/BSA emulsion increased slightly during storage at 25 °C. Further, 0.20 wt% TPC/BSA emulsions became less stable after heat treatment, whereas the particle size of other concentrations did not change significantly after treatment at 70 ℃–90 °C. TPC/BSA emulsions were more stable at pH 6.0–9.0. Both were less affected by Na+, weakly affected by Ca2+ than BSA emulsion, and significantly affected by Al3+. TPC/BSA emulsion had a good protection effect on EGCG and EGC. The presence of EGCG and EGC improved the stability of the emulsion system, which remained stable for 90 days.

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.

Molecular insights into the α-glucosidase inhibition and antiglycation properties affected by galloyl moiety in (-)-epigallocatechin-3-gallate.

Diabetes mellitus poses a substantial threat to public health due to rising morbidity and mortality. α-Glucosidase is one of the key enzymes affecting diabetes. Herein, (-)-epigallocatechin-3-gallate (EGCG) and (-)-epigallocatechin (EGC) were applied to clarify the role of galloyl moiety of tea polyphenols in the inhibition of glycation and α-glucosidase activity. The structure-activity relationship of the galloyl moiety in (-)-epigallocatechin-3-gallate (EGCG) on α-glucosidase was investigated in terms of inhibition kinetics, spectroscopy, atomic force microscopy and molecular docking. Bovine serum protein-fructose model was employed to determine the effect of the galloyl moiety on glycation. The results indicated that the introduction of a galloyl moiety enhanced the capacity of EGCG to inhibit glycation and α-glucosidase activity. The IC50 value of EGC is approximately 2400 times higher than that of EGCG. Furthermore, the galloyl moiety in EGCG altered the microenvironment and secondary structure of α-glucosidase, resulting in a high binding affinity of EGCG to α-glucosidase. The binding constant of EGCG to α-glucosidase at 298 K is approximately 28 times higher than that of EGC. Overall, the galloyl moiety of EGCG plays a crucial role in inhibiting glycation and α-glucosidase activity, which helps to enhance the molecular understanding of the structure and function of the polyphenol galloyl moiety in the science of food and agriculture. This article is protected by copyright. All rights reserved.