Addition Of Epigallocatechin Gallate Research Articles

The effect of epigallocatechin gallate on Streptococcus Gordonii biofilm formation

Background: Dental caries, as a primary disease in dentistry, is strongly influenced by the presence of biofilms. One of the Gram-positive bacteria that acts as an initiator in the biofilm formation process is Streptococcus gordonii. As the primary catechin in green tea, epigallocatechin gallate (EGCG) is easily found in our daily lives, and it has a broad spectrum of antimicrobial effects. Several studies have revealed that EGCG inhibited the growth of Gram-positive bacteria, including inhibiting biofilm formation by damaging the bacterial cell wall and reducing glucosyltransferase activity. However, there is still limited information that explains the effect of EGCG on S. gordonii bacterial biofilms. Purpose: This study aims to analyze the effect of EGCG in inhibiting the formation of S. gordonii bacterial biofilms. Methods: This study was an in-vitro experimental laboratory study, with samples divided into five groups, namely, the group containing BHIB-bacteria, the BHIB-bacteria-5% sucrose groups, and the treatment groups containing BHIB-bacteria-5% sucrose-EGCG with concentrations of 12.5%, 6.25%, and 3.125%, respectively, incubated for 24 hours. The data was analyzed using the Kruskal–Wallis test. Results: There was a significant difference in the formation of biofilms in S. gordonii bacteria with the addition of 5% sucrose in BHIB compared with the group of S. gordonii bacteria in BHIB. The highest biofilm formation in the group containing bacteria-BHIB-5% sucrose, while the lowest biofilm formation occurred in the treatment group containing bacteria-BHIB-5% sucrose-12.5% EGCG with significant difference between the group. Conclusion: The addition of EGCG 12.5% inhibits the formation of S. gordonii biofilms.

In Vitro Effect of Epigallocatechin Gallate on Heme Synthesis Pathway and Protoporphyrin IX Production.

Photodynamic therapy (PDT) treats nonmelanoma skin cancer. PDT kills cells through reactive oxygen species (ROS), generated by interaction among cellular O2, photosensitizer and specific light. Protoporphyrin IX (PpIX) is a photosensitizer produced from methyl aminolevulinate (MAL) by heme group synthesis (HGS) pathway. In PDT-resistant cells, PDT efficacy has been improved by addition of epigallocatechin gallate (EGCG). Therefore, the aim of this work is to evaluate the effect of EGCG properties over MAL-TFD and PpIX production on A-431 cell line. EGCG's role over cell proliferation (flow cytometry and wound healing assay) and clonogenic capability (clonogenic assay) was evaluated in A-431 cell line, while the effect of EGCG over MAL-PDT was determined by cell viability assay (MTT), PpIX and ROS detection (flow cytometry), intracellular iron quantification and gene expression of HGS enzymes (RT-qPCR). Low concentrations of EGCG (<50 µM) did not have an antiproliferative effect over A-431 cells; however, EGCG inhibited clonogenic cell capability. Furthermore, EGCG (<50 µM) improved MAL-PDT cytotoxicity, increasing PpIX and ROS levels, exerting a positive influence on PpIX synthesis, decreasing intracellular iron concentration and modifying HGS enzyme gene expression such as PGB (upregulated) and FECH (downregulated). EGCG inhibits clonogenic capability and modulates PpIX synthesis, enhancing PDT efficacy in resistant cells.

EGCG induced the formation of protein nanofibrils hydrogels with enhanced anti-bacterial activity

The functional properties of the amyloid fibrils could be further improved after physical modification. Simply adding epigallocatechin gallate (EGCG) to ovalbumin amyloid fibrils (OAFs) could successfully drive the formation of hydrogels through the self-assembly of hybrid supermolecules, however the functional properties of amyloid fibrils as well as the underlying formation mechanisms have not been well revealed. In present study, the rheological properties, thermal stability, and morphology of the resulting OAFs hydrogels were investigated, and the secondary structural changes of the proteins in OAFs hydrogels was analyzed. The results showed that the addition of EGCG would affect the diameter of OAFs, mainly as the concentration of EGCG increased from 0.1% to 2%, the diameter of OAFs increased from 3 nm to 5.5 nm. In addition, when the EGCG concentration increased from 0.1% to 0.5%, the content of β-sheet structure increased from 24.3% to 43.7%. Moreover, the OAFs hydrogels exhibited good viscoelasticity and heat resistance, as well as displayed good antioxidant activity and strong anti-bacterial activity against both Gram-negative and Gram-positive bacteria. The present study might provide a theoretical basis for antimicrobial food packaging based on animal amyloid fibrils hydrogels.

Cryoprotective effect of epigallocatechin gallate replacing sucrose on Hypophythalmichthys molitrix surimi during frozen storage.

The present study aimed to investigate the cryoprotective effect of epigallocatechin gallate (EGCG) replacing sucrose on surimi during frozen storage. Substitution or partial substitution of 0.1% EGCG for sucrose (1.5%) was added to surimi, and the surimi samples without and with commercial cryoprotectants (4% sucrose and 4% sorbitol) were used as the control group. The results obtained suggest that, with the increase in frozen storage time, the structural performance of surimi protein gradually weakened (e.g. the decrease in the surface hydrophobicity, the increase in the total sulfhydryl and solubility, and the protein myosin heavy chain bands became shallow) and surimi gel quality gradually deteriorated (e.g. the decrease in water-holding capacity, gel strength and all texture profile attributes). However, compared with the other three group surimi samples during the frozen period, the surimi proteins with partial replacement of sucrose by EGCG had a higher total sulfhydryl group content and solubility of proteins, as well as lower surface hydrophobicity of protein, suggesting that the addition of EGCG as a partial substitute for sucrose can enhance the antifreeze ability of surimi. Meanwhile, the surimi gel with the partial replacement of sucrose by EGCG had a higher water retention capacity, gel strength and texture attributes (e.g. hardness, springiness, cohesiveness, chewiness, and resilience), indicating that the addition of EGCG as a partial substitute for sucrose can inhibit the deterioration of surimi gel quality. Overall, EGCG partially replacing sucrose can play an alternative cryoprotectant with a lower sweetness to prevent the quality of surimi from deteriorating. © 2024 Society of Chemical Industry.

Community-engaged basic science in an NCI-designated comprehensive cancer center: antioxidants and chemotherapeutic efficacy.

While community engagement has been a longstanding aspect of cancer-relevant research in social and behavioral sciences, it is far less common in basic/translational/clinical research. With the National Cancer Institute's incorporation of Community Outreach and Engagement into the Cancer Center Support Grant guidelines, successful models are desirable. We report on a pilot study supported by the University of Maryland Greenebaum Comprehensive Cancer Center (UMGCCC), that used a community-engaged, data-driven process to inform a pre-clinical study of the impact of antioxidants on the efficacy of platinum-based chemotherapeutics. We conducted a survey of UMGCCC catchment area residents (n = 120) to identify commonly used antioxidants. We then evaluated the effect of individually combining commonly used antioxidants from the survey (vitamin C, green tea, and melatonin) with platinum agents in models of non-small cell lung cancer (A549), colon adenocarcinoma (SW620) and head and neck squamous cell carcinoma (FaDu). In vitro, the anti-neoplastic activity of each chemotherapy was not potentiated by any of the antioxidants. Instead, when combined at fixed ratios, most antioxidant-chemotherapy combinations were antagonistic. In vivo, addition of antioxidants did not improve chemotherapeutic efficacy and in a FaDu-tumor bearing model, cisplatin-mediated tumor growth inhibition was significantly impeded by the addition of epigallocatechin gallate, the main antioxidant in green tea. These initial findings do not support addition of antioxidant supplementation to improve platinum-based chemotherapeutic efficacy. This study's approach can serve as a model of how to bring together the two seemingly discordant areas of basic research and community engagement.

Preparation and characterization of egg white protein film incorporated with epigallocatechin gallate and its application on pork preservation.

The aim of this study was to develop the composite films with antioxidant and biodegradable activity based on egg white protein (EWP) and epigallocatechin gallate (EGCG). Water susceptibility, light transmittance, microstructure and antioxidant properties of the composite films without and with EGCG were fully characterized. It was noted that the addition of EGCG might decrease the moisture content, water solubility and swelling capacity. SEM micrographs revealed that discontinuous blocks and rough surfaces were caused by increasing concentration of EGCG, whereas compact and homogeneous particles appeared when the concentration of EGCG reached to 80μmol/L. Moreover, the biodegradability of the composite films was demonstrated by the soil degradation properties that they can be almost completely degraded within ten days. Experimental results on the application in chilled fresh pork showed that the EWP-based films could play an antioxidant role when incorporated with EGCG, indicating their great potential for food packaging.

Dual stimulus responsive borosilicate glass (BSG) scaffolds promote diabetic alveolar bone defectsrepair by modulating macrophage phenotype

The regeneration of alveolar bone is still clinical challenge, particularly accompanied with diabetes, causing metabolic disorder with a protracted low-grade inflammatory phenotype. As a result, the anticipated loading of biomaterials is highly suspicious in spontaneous modulation of cells function, which is mostly disturbed by constant inflammation. In this study, we developed glucose and hydrogen peroxide dual-responsive borosilicate glass (BSG) scaffolds loaded with epigallocatechin gallate (EGCG) to synergistically modulate the abnormal inflammation of diabetic alveolar bone defects. It was found that the release of EGCG by BSG could directly regulate the shift of macrophages from M1 to the M2 phenotype by promoting autophagy and lessening the inhibition of autophagic flux. Moreover, EGCG can also indirectly regulate the polarization phenotype of macrophages by reducing the activation of NF-κb in stem cells and restoring its immunoregulatory capacity. Therefore, the addition of EGCG to BSG scaffold in diabetes allows for a more striking modulation of the macrophage phenotype in a timely manner. The altered macrophage phenotype reduces local inflammation and thus increases the ability to repair diabetic alveolar bone, showing promise for the treatment of alveolar defect in diabetic patients.

Influence of Epigallocatechin Gallate on Quality of Cooked Harpiosquillid Mantis Shrimp (Harpiosquilla raphidea) Subjected to Multiple Freeze-Thaw Cycles

Effects of epigallocatechin gallate (EGCG) at 200 or 400 ppm on quality changes of cooked Harpiosquillid mantis shrimp (Harpiosquilla raphidea) (CHMS) meat subjected to varying freeze-thaw cycles (F-T-C; 0, 1, 3, and 5) were studied. With augmenting F-T-C, the CHMS meat underwent deterioration to higher extent as indicated by upsurges in exudate loss, tougher texture along with increased microbial counts. The addition of EGCG could retard those changes in a dose-dependent manner. Furthermore, EGCG prevented microbial growth as ascertained by lower counts and total volatile basic nitrogen (TVB) content. Lipid oxidation was also impeded in the presence of EGCG, especially at a high concentration as evidenced by lowered malondialdehyde (MDA), while maintaining polyunsaturated fatty acids, particularly EPA and DHA when F-T-C raised. Total disulfide bond content and surface hydrophobicity of CHMS added with EGCG were lower than those of the control. Those alterations were more retarded as EGCG concentration increased. Therefore EGCG at 400 ppm effectively prevented quality loss of CHMS meat during repeated F-T process.

The EGCG and α-Mangosteen Stimulate SHED-IL10 and SHED-LL37 Metabolite Concentration.

Stem cells of human exfoliated deciduous teeth (SHED) metabolites are secreted molecules from SHED, namely cytokines, chemokines, and growth factors. The metabolite can be used in various regenerative therapy based on cell-free immunomodulatory potential effects, like interleukin 10 (IL-10) and LL37. This molecule can stimulate with epigallocatechin gallate (EGCG) and α-mangosteen and has been proven to have anti-inflammatory and antibacterial effects. This study aimed to identify the effect of EGCG and α-mangosteen to SHED metabolite, called SHED-IL10 and SHED-LL37, from six passages to obtain the optimum stimulation and able to use as periodontitis regeneration treatment. The six different passages of SHED were prepared in Dulbecco's modified Eagle medium and added with EGCG 80% (10 μM), EGCG 95% (10 μM), or α-mangosteen (10 μM). After a 24 hours incubation, each passage was measured with the metabolite concentration, SHED-IL10 and SHED-LL37, with human IL-10 and LL37 using enzyme-linked immunosorbent assay. Each different concentration was then analyzed statistically. The addition of EGCG 95% is able to stimulate the SHED-IL10 optimum concentration in passage 1 (p < 0.01). But, in the different conditions, the addition of EGCG 80%, EGCG 95%, and α-mangosteen was able to stimulate the SHED-LL37 optimum concentration in passage 2 (p < 0.001). The addition of EGCG and α-mangosteen can stimulate the SHED-IL10 and SHED-LL37 concentrations. These two metabolites are promising as regenerative therapy through anti-inflammatory and antibacterial properties.

Abstract 2845: PpIX synthesis increases PDT resistant cells due to the modulating effect of EGCG on the heme synthesis pathway

Abstract Introduction: Photodynamic therapy (PDT) is a treatment for non melanoma skin cancer. PDT kills cells through reactive oxygen species (ROS), produced by interaction between cellular O2 and an excited photosensitizer (PS) by a specific light. One of the most used PS in dermatology is Protoporphyrin IX (PpIX) and its precursor methyl aminolevulinate (MAL). MAL enters into cells and is converted to PpIX by enzymes of the heme group synthesis pathway. The insertion of ferrous iron into PpIX forms a heme molecule, which has no PS action. A previous study shows that efficacy of PDT, in resistant cells, can be improved by addition of epigallocatechin gallate (EGCG), a green tea polyphenol. Therefore, the aim of this work is to evaluate the rol of EGCG on PPIX synthesis. Material and methods: It was used a A-431 cell line from skin squamous cell carcinoma. The EC50 of EGCG was determined by MTT assay after 24 hours. Clonogenic assay was carried out using EGCG 10, 20 and 40 μM, for 4 and 24 hours of incubation. To evaluate PpIX and ROS, A-431 cells were exposed to EGCG (10, 20, 40 μM) with or without MAL 2 mM. After 4 hours, some plates were irradiated with red light to generate ROS. PpIX and ROS were detected by flow cytometry. Gene expression of enzymes of heme synthesis was analyzed by RT-qPCR. Intracellular iron was measured using a commercial kit.  Results: EC50 determined a concentration of 50 μM of EGCG at 24 hours. EGCG concentrations from 10 μM reduced cell clonogenic capacity, even with only 4 hours of incubation. A-431 cells show PDT resistance with MAL 2 mM and a fluence of 4 J/cm2. The addition of EGCG to MAL-PDT showed a decrement of cell viability with an increase of PpIX and ROS. Besides, incubation with EGCG for 4 hours, triggered an increment of HMBS enzyme and decrease of FECH. In addition, EGCG reduced intracellular iron concentrations. Conclusion: These findings show that EGCG has a PDT enhancing effect, decreasing intracellular iron levels and modulating gene expression of heme synthesis enzymes, which are directly related with high levels of PpIX production and ROS levels, causing the death of resistant cells.Acknowledgements: Postdoctoral FONDECYT Nº 3210618, IDeA I+D FONDEF ID21I10027 Citation Format: Daniela León, Álvaro Gutiérrez, Helga Weber, Ramón Silva, María Elena Reyes, Tamara Viscarra, Kurt Buchegger, Carmen Ili, Priscilla Brebi. PpIX synthesis increases PDT resistant cells due to the modulating effect of EGCG on the heme synthesis pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2845.

Abstract 2422: In vivo pilot study of the effect of EGCG in photodynamic therapy on non melanoma skin cancer

Abstract Non-melanoma skin cancer (NSCLC) is the most frequent cancer in humans worldwide. Solar UV radiation is main risk factor to NSCLC developing in areas such as the face, neck, arms, etc. Basal cell carcinoma and precursor lesions of squamous cell carcinoma (SCC), such as actinic keratosis, Bowen’s disease, etc. can be treated with Photodynamic Therapy (PDT). PDT consists of applying a cream containing a photosensitizer on the skin lesion, to then being irradiated with light at a specific wavelength. The most used PS in skin cancer is methyl aminolevulinate (MAL). Light excites the photosensitizer, which interacts with intracellular O2, producing reactive oxygen species (ROS), triggering cancer cell death. One of the main advantages of PDT is that it offers satisfactory cosmetic results. However, its effectiveness is variable. Our previous results, using a PDT-resistant SCC cell model, showed that the addition of epigallocatechin gallate (EGCG) to PDT has a potentiated effect, killing 100% of these cells. Therefore, the aim of this work was to evaluate the effect of an EGCG-enhanced cream for PDT on squamous cell carcinoma lesions in an animal model.A two-step chemical carcinogenesis protocol (DMBA/TPA) was used in male and female mice of the Balb/c strain (21 animals). Once the animals developed the desired lesions, they were randomly separated into three groups. The first group received conventional cream (MAL 20%), the second group cream A (MAL 20% + EGCG 1%) and the third group B cream (MAL 20% + EGCG 3%). PDT was performed as follows: cream was applied for 4 hours on the lesion and then protected from the light with a patch. Subsequently, the excess cream was removed and the lesions were irradiated with 630 nm red light. The lesions were followed up for one month, measuring the size of the tumor and taking a final biopsy.We successfully develop an in vivo model of NSCLC using chemical inducers. Mice develops two kind of lesions: plane and/or papillar. All mice were treated with PDT using the three different formulations. Lesions reduced its size until a 50% more when treated with PDT plus EGCG. Formulation B (MAL 20% + EGCG 3%), was the most effective, given it had a greater on the relative reduction of the volume of the lesion. In conclusion, this in vivo pilot study evidences the enhancing effect of EGCG on PDT, encouraging the pursue to continue with the investigations on this matter, in order to improve the PDT and the quality of life of skin cancer patients. Citation Format: Carmen Gloria Ili, Daniela Leon, Maria Elena Reyes, Kurt Buchegger, Francisca Acevedo-Canala, Pablo Guzman, Claudia Nicklas, Cecicia Orlandi, Priscilla Brebi. In vivo pilot study of the effect of EGCG in photodynamic therapy on non melanoma skin cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2422.

Fabrication and characterization of gelatin-EGCG-pectin ternary complex: formation mechanism, emulsion stability, and structure.

Protein-polyphenol-polysaccharide ternary complex particles have better emulsion interfacial stability compared to protein-polysaccharide binary complexes. However, knowledge is scarce when it comes to the fabrication of protein-polyphenol-polysaccharide ternary complexes as interfacial stabilizers and the interactions between the three substances. In the present work, ternary complexes were prepared using gelatin, high methoxyl pectin, and epigallocatechin gallate (EGCG) as raw materials. The effect of different influencing factors on the formation process of ternary complexes was investigated by varying different parameters. physicochemical stability, emulsifying properties, and structural characteristics were analyzed. The ternary complex had a smaller particle size (275 nm) and polydispersity index (0.112) when the mass concentration ratio of gelatin to high methoxyl pectin was 9:1, addition of EGCG was 0.05%, pH value was 3.0, and ionic strength was 10 mmol L-1 . Meanwhile, the complex had the highest emulsifying stability index (691.75 min) and emulsifying activity index (22.96 m2 g-1 ). Scanning electron microscopical observation demonstrated that the addition of EGCG promoted the dispersion of ternary complex more uniformly, and effectively reduced the agglomeration phenomenon. The discrepancy in fluorescence intensity suggested that interactions between EGCG and gelatin occurred, which altered the protein spatial conformation of gelatin. Fourier transform infrared spectroscopic analysis elucidated that hydrogen bond interaction was the primary non-covalent interaction between EGCG and gelatin-high methoxyl pectin binary complex. The aforementioned results purposed to provide some theoretical reference and basis for the rational design of stable protein-polyphenol-polysaccharide ternary complexes. © 2022 Society of Chemical Industry.

Epigallocatechin gallate (EGCG) modification of structural and functional properties of whey protein isolate

The objective of this paper was to investigate the interactions between (-)-Epigallocatechin-3-gallate (EGCG) and whey protein isolate (WPI) by covalent and non-covalent combinations and the effects of the interactions on the conformational and functional changes of whey protein. Conformational changes in the secondary structure of whey protein with various concentrations of EGCG were studied using FTIR spectra. EGCG was more likely to form covalent bonds than non-covalent bonds when it interacted with whey proteins. The addition of EGCG altered the conformation of whey protein. The content of β-sheet decreased, while that of β-turn increased, however, the random coil remained unchanged. An reduction in surface hydrophobicity was observed in all the WPI-EGCG complexes, suggesting that modification in secondary structure of WPI were induced by EGCG. Additionally, the emulsifying and foaming attributes of WPI were enhanced after interaction with EGCG. This study confirms that EGCG can enhance the functional properties of WPI. It is also a pointer to the possible application of WPI-EGCG complexes in the dairy industry.

Assessing the Gel Quality and Storage Properties of Hypophythalmalmichthys molitrix Surimi Gel Prepared with Epigallocatechin Gallate Subject to Multiple Freeze-Thaw Cycles.

Epigallocatechin gallate (EGCG) with concentrations of 0–0.03% was added to manufacture surimi gels, respectively, while effects on gel quality and storage properties indicators during freeze-thaw (F-T) cycles were investigated. The results implied that the gel quality and storage properties of surimi gels added without EGCG were seriously destroyed during F-T cycles. The addition of EGCG could inhibit the decline of texture and gel strength. Moreover, EGCG has effect on inhibiting the microbial growth and the formation of off-odor compounds such as total volatile basic nitrogen (TVB-N) and malondialdehyde (MDA). Low-field nuclear magnetic resonance (LF-NMR) and water-holding capacity (WHC) results showed that immobilized water migrated to free water with the extension of F-T cycles. The scanning electron microscope (SEM) observed denser protein networks and smaller holes from the surimi gels added with EGCG. However, excessive (0.03%) EGCG showed the loose network structure and moisture loss. Overall, EGCG in 0.01–0.02% addition was good for resisting damage of surimi gels during F-T cycles.

Preparation and characterization of chitosan films incorporating epigallocatechin gallate: Microstructure, physicochemical, and bioactive properties

Novel chitosan films incorporating epigallocatechin gallate (EGCG) were prepared and demonstrated the ideal physical and mechanical properties required of candidate food packaging materials alongside desirable antioxidant and antibacterial activity. Compared with traditional chitosan films, chitosan films incorporated with EGCG were thicker, had higher tensile strength and water solubility, and had lower elongation at break, moisture content, degree of swelling, and water contact angles. Although EGCG-containing films were slightly darker in color than pure chitosan films, they exhibited a greater inhibitory effect on light-induced oxidation with obviously improved UV–vis barrier capability and opacity. Scanning electron microscopy results suggested that EGCG-incorporated samples had a rougher surface structure. This was further confirmed by atomic force microscopy and indicated that the addition of EGCG facilitated the formation of protective barriers through the interaction between the film and food surface. FTIR spectroscopy confirmed that EGCG interacted with chitosan by intermolecular hydrogen bonding and effectively improved the thermal stability of chitosan films. Notably, the incorporation of EGCG significantly enhanced the antioxidant and antibacterial activity of chitosan films. Hence, chitosan films incorporating EGCG have potential applications in the food industry as a novel active packaging material, especially in preventing food oxidation and spoilage in perishable foods.

The antiviral effect of catechins on mumps virus infection

• The inhibitory effect and its mechanism of catechins on mumps virus infection. • Epigallocatechin gallate shows the highest antiviral potency. • A galloyl group in catechins is an important factor for the strong antiviral effect. • The antiviral effect can result from inhibition of the viral fusion activity. Catechins have been known to possess antiviral effects against influenza A and B viruses through the inhibition of both the viral receptor binding and viral sialidase activities. Here, we examined the antiviral effect of catechins on mumps virus infection. The addition of epigallocatechin gallate (EGCG), gallocatechin gallate, epicatechin gallate, or catechin gallate simultaneously with the mumps virus infection of Vero cells greatly inhibited the infection. EGCG showed the strongest antiviral effect among the catechins tested. These catechins did not exhibit an inhibitory effect against the receptor binding and sialidase activities in the hemagglutinin–neuraminidase of the mumps virus, which was different from a known mechanism for influenza A and B viruses. By contrast, these catechins inhibited the viral fusion activity. Our results indicate that catechins are a useful food-derived antiviral agent against the mumps virus.

The inhibition effect of tea polyphenols on soil nitrification is greater than denitrification in tea garden soil.

Tea polyphenols are the most widely distributed class of secondary metabolites (Camellia sinensis) and account for a considerable proportion of the pruning residues of tea. A large amount of tea polyphenols have fallen down over soil with prunning residues every year. However, the effect of tea polyphenols on soil nitrogen cycle, especially the denitrification process and its related microbial communities, remains unclear. Epigallocatechin gallate (EGCG), the most abundant component of tea polyphenols, was selected to simulate the effects of tea polyphenols on soil nitrification, denitrification, related functional genes and microbial community. The results indicated that addition of EGCG can significantly (p<0.05) inhibit soil nitrification. Copy numbers of bacterial and archaeal ammonia monooxygenase genes (amoA) decreased as EGCG concentration increased. Further, the ammonia oxidisers exhibited a significantly (p<0.05) greater niche differentiation under the effect of EGCG compared with the control treatment (no EGCG addition). However, the inhibition effect of EGCG over soil denitrification was most significant at 34 and 36day of incubation period, and such inhibitory effect was more apparent on nitrification compared with denitrification. EGCG addition increased the diversity of bacterial community. The composition of bacterial community was significantly altered and community variation was primary explained by EGCG, NH4+-N, NO3--N, soil organic carbon contents and potential denitrification rates. EGCG addition significantly increased relative abundance of Proteobacteria and Bacteroidetes phyla whereas decreased Actinobacteria. Overall, tea polyphenols can inhibit soil nitrification to a larger extent than denitrification by reducing the abundance of microorganisms carrying the related functional genes. Our results can serve as important basis of reducing the nitrogen pollution risk in tea orchards and could be considered as a powerful natural nitrification inhibitor to reduce the environmental risks caused by unreasonable nitrogen fertiliser adaptation.

Effects of epigallocatechin gallate incorporation in UHMWPE on biological behavior, oxidative degradation, mechanical and tribological performance for biomedical applications

Oxidation of ultrahigh-molecular-weight-polyethylene (UHMWPE) affects its physicochemical properties. Epigallocatechin gallate (EGCG) was added to improve UHMWPE antioxidant capacity. The extract of UHMWPE stabilized with EGCG (EGCG/UHMWPE) exhibits cytocompatibility and cell viability in vitro. The gamma irradiated UHMWPE and EGCG/UHMWPE present similar physicochemical properties. Mechanical and tribological properties of irradiated pure UHMWPE are deteriorated after accelerated aging, while these properties are maintained after adding EGCG. The wear mechanism of irradiated UHMWPE is mainly abrasive and fatigue wear after accelerated aging, while the addition of EGCG improves the fatigue resistance and reduces the number of flakes and ruptures of irradiated UHMWPE.

Sensing of epigallocatechin gallate and tannic acid based on near infrared optical spectroscopy of DNA-wrapped single-walled carbon nanotube hybrids

The optical responses of DNA-wrapped single-walled carbon nanotubes (DNA-SWNTs) caused by the addition of epigallocatechin gallate (EG) and tannic acid (TA) were investigated. Near infrared absorbance and photoluminescence spectra of pre-oxidized DNA-SWNTs were measured with and without EG and TA. Since both EG and TA have antioxidant abilities, the near infrared spectra changed after the addition of the chemicals. While detection of the antioxidant abilities of EG by DNA-SWNT hybrids has been previously reported, TA was employed for the first time. The changes in the absorbance caused by the addition of TA were found to saturate at 0.33 µM TA, although saturation was not observed even at 3.3 µM with the addition of EG. Oxidation of DNA-SWNT was suppressed by addition of TA or EG. The effects of TA were much greater than those of EG on the absorbance. The photoluminescence did not appear to saturate at 3.3 µM for either EG or TA. photoluminescence had a larger measurement capacity than NIR absorbance. Interestingly, the photoluminescence change caused by EG was much larger than that of TA at 3.3 µM, although the antioxidant property of TA was stronger at 0.33 and 0.033 µM, suggesting that the optical responses were not simple redox reactions. Peak shifts in the absorbance/photoluminescence spectra revealed unique differences according to the chirality of the SWNTs and the types of chemicals used. This suggests that the combination of absorbance/photoluminescence and peak intensity/peak shifts could detect multiple types of chemical information, not only redox reaction. A direct comparison between EG and TA was demonstrated for the first time in this novel study. In addition, sensing of EG and TA by near infrared spectra was made available using not only changes in intensity but also a variety of peak shifts of SWNTs.

Effects of soybean protein isolate − polyphenol conjugate formation on the protein structure and emulsifying properties: Protein − polyphenol emulsification performance in the presence of chitosan

Herein, we investigated the influence of covalent complexation between (−)-epigallocatechin gallate (EGCG) and soy protein isolate (SPI) on the structural and emulsifying properties of the protein as well as the effect of chitosan (CS) on the stability of emulsions formed by the covalent conjugates. The formation of the covalent complex of SPI and EGCG was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three-dimensional fluorescence spectroscopy and circular dichroism spectroscopy were conducted to analyze the changes in the protein structure at different EGCG concentrations (0.005, 0.015, and 0.025 wt%). The addition of EGCG changed the tertiary conformation and secondary structure of the protein—unfolding of the protein polypeptide chain, decrease in the β-strand content, and increase in α-helix and random coil contents were observed. After covalent bonding of SPI with EGCG (0.015 wt %), the complex exhibited optimal solubility and emulsifying properties. SPI–EGCG–CS emulsions were prepared by layer-by-layer electrostatic assembly at pH 5.0. The effect of environmental stress on the stability of the CS–loaded SPI–EGCG (0.015 wt%) emulsion oil droplets was studied by freezing (−20 ℃, pH 5) and thermal treatment (90 ℃, 30 min, pH 5). The stability of the emulsion was improved when the CS concentration was >0.25 wt%; this improvement was attributed to the increase in electrostatic force and steric hindrance among droplets and the formation of a relatively thick biopolymer interface on the surface of oil droplets. In addition, the rheological properties showed that thicker interface layers and network structures caused deviations from the flow behavior of emulsions. These results indicate that SPI − EGCG conjugates can be used as food additives and for the construction of the lipophilic active ingredient delivery system.