Concentrations Of Green Tea Extract Research Articles

Characterization of a Corn Fiber Protein Film Containing Green Tea Extract

Corn fiber protein (CFP) was extracted from corn wet-milling by-product, corn fiber. CFP films containing various plasticizers and cross-linking agents were prepared and their mechanical properties were determined. Among the plasticizers and cross-linking agents used in this study, the CFP film containing 2 g fructose and 0.03% cinnamaldehyde had the most appropriate physical property. In addition, the CFP films containing green tea extract (GTE) were prepared by incorporating different amounts (0, 0.5, 1.0, 1.5%) of GTE into the film-forming solution. Tensile strength, film solubility, and opacity of the CFP films increased with the addition of GTE, whereas elongation and water vapor permeability of the CFP/GTE films decreased compared to those of the control. The antioxidant activity of the CFP/GTE film was determined in terms of 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity. As a result, antioxidant activity of the films increased with increasing GTE concentration. Furthermore, antimicrobial activity against Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus increased with increasing GTE concentration. These results indicate that the incorporation of GTE could enhance antioxidant and antimicrobial activities of the CFP films.

The Making of Transparent Soap from Green Tea Extract

This study aims to determined the effect of green tea extract on the characteristics of transparent soap and antioxidant activity as well as to determine the best concentration of the addition of green tea extract. This study used a completely randomized design (CRD) consisting of 5 treatments and 3 repetitions. Data were analyzed statistically using ANOVA followed by Duncan's test New Multiple Range Test (DNMRT) at 5%. Treatment in this research were the addition of green tea extract 0%; 0.5%; 1%; 1.5%; and 2%. The analysis on the transparent soap product were sensory evaluation test, irritation test, antimicrobial test, antioxidant activity, and chemical properties that include water content, pH, the amount of fatty acid, the saponified fraction, alkali-free / free fatty acids, and insoluble part in alcohol . The results showed that the difference in the concentration of green tea extract in a transparent soap significantly affect insoluble part in alcohol, antioxidant activity, and antimicrobial, but did not significantly affect to moisture content, the level of fatty acid , unsaponified fraction, free fatty acids, pH, hardness , and degree of foam. Effect of green tea extracts in the manufacture of transparent soap in treatment E (Addition of green tea extract 2%) is the best product, the value for color was 25%, aroma was 50%, 20% transparency, hardness 35%, and degree of foam was 70while the hardness was 2,90 N / cm2; degree of foam 48.95%; the water content of 35.35%; 29.78% the amount of fatty acids; unsaponified fraction was 12.87%; free fatty acids 0,23%; pH was 9.78; Insoluble parts in alcohol 2.08%; irritation value 0; antioxidant activity of 15.21% and a diameter anti-microbial of 42 mm. A transparent soap with the addition of green tea extract deserves to be developed.

Development of an active food packaging system with antioxidant properties based on green tea extract

A formula including green tea extract (GTE) was developed as an active food packaging material. This formula was moulded to obtain an independent component/device with antioxidant properties that could be easily coupled to industrial degassing valves for food packaging in special cases. GTE components (i.e., gallic acid, catechins and caffeine) were identified and quantified by HPLC-UV and UPLC-MS and migration/diffusion studies were carried out. Antioxidant properties of the formula alone and formula-valve were measured with static and dynamic methods. The results showed that the antioxidant capacity (scavenging of free radicals) of the new GTE formula was 40% higher than the non-active system (blank). This antioxidant activity increased in parallel with the GTE concentration. The functional properties of the industrial target valve (e.g., flexibility) were studied for different mixtures of GTE, and good results were found with 17% (w/w) of GTE. This new active formula can be an important addition for active packaging applications in the food packaging industry, with oxidative species-scavenging capacity, thus improving the safety and quality for the consumer and extending the shelf-life of the packaged food.

A Comparative Study for the Effect of Green Tea Extract and Some Antioxidants on Thompson Seedless Grapevines

Leaf area, plant pigments, leaf content of N, P, K, Mg, Ca, Zn, Fe and Mn, yield and berry quality of Thompson seedless grapevines in response to spraying green tea extract, ascorbic acid and citric acid each at 250 to 1000 ppm as well as salicylic acid at 50 to 200 ppm were investigated during 2012 and 2013 seasons. Spraying green tea extract or any one of the three antioxidants was very effective in stimulating the leaf area, plant pigments, all nutrients in the leaves, yield as well as physical and chemical characteristics of the grapes in relative to the check treatment. The promotion was associated with using ascorbic acid, green tea extract, salicylic acid and citric acid, in descending order. In all cases, no clear effect was detected on all the investigated parameters among the higher two concentration of green tea extract and the three antioxidants. Treating Thompson seedless grapevines three times with ascor bic acid at 500 ppm or green tea at the same concentration is suggested to be beneficial for promoting yield quantitively and qualitively.

In Vitro Inhibitory Activity of the Leaf Methanol Extract of Green Tea (<i>Camellia sinensis</i>) against <i>Lactococcus garvieae</i> and <i>Aeromonas hydrophila</i> Isolated of Rainbow Trout (<i>Oncorhynchus mykiss</i>)

Camellia sinensis Linn is a well-known medical herb that grows in various parts of the world. In the current study, the antimicrobial activity of methanol extract from C. sinensis leaves against Lactococcus garvieae and Aeromanas hydrophila isolated from rainbow trout (Oncorhynchus mykiss) was investigated. The growth inhibitory effects of green tea extract was determined by disc diffusion method (3 times on different days), minimum inhibitory concentration (MIC) using serial dilution and minimum bactericidal concentration (MBC). For the L. garvieae and A. hydrophila, the zone diameter inhibition (ZDI) of extract ranged 2.30 - 16.5 mm. The highest ZDI (16.50 ± 1.12 mm) for L. garvieae was observed at 100 mg•ml-1 and for A. hydrophila (16.20 ± 0.95 mm) at 250 mg•ml-1 concentration of green tea extract (P •ml-1 concentrations of extract, ZDI values of A. hydrophila and L. garvieae showed significant difference (P •ml-1 against both L. garvieae and A. hydrophila. From the results of the present study, it can be concluded that methanol extract of C. sinenses leaves could be effective for the inhibition of A. hydrophila and L. garvieae in rainbow trout.

An in vitro comparative antibacterial study of different concentrations of green tea extracts and 2% chlorhexidine on Enterococcus faecalis

Aim : The purpose of this study was to comparatively evaluate the antibacterial property of various concentrations of green tea extracts and 2% chlorhexidine (CHX) against Enterococcus faecalis 0(E. faecalis) in vitro. Materials and Methods: The activity of green tea extract and CHX on E. faecalis was measured on agar plates using the agar diffusion method. In addition, the tube dilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration of green tea extract against E. faecalis. Results: The MIC of green tea extract was found to be 3.5%. The zone of inhibition was found to be concentration dependent. The 2.5% concentration of green tea extract showed 20 mm zone of inhibition, while the 3% concentration demonstrated a 30 mm zone of inhibition. Two percent CHX showed 30 mm zone of inhibition. Conclusion: Three percent concentration of green tea extract showed an antibacterial activity equivalent to 2% CHX against E. faecalis.

Inhibitory Activity of Green Tea (Camellia sinensis) Extract on Some Clinically Isolated Cariogenic and Periodontopathic Bacteria

Objective: To determine the in vitro inhibitory activity of green tea extract on some clinically isolated cariogenic and periodontopathic bacteria. Materials and Methods: Twenty strains of each of Streptococcusmutans, Aggregatibacteractinomycetemcomitans, Porphyromonasgingivalis, and Prevotellaintermedia were isolated from carious teeth and periodontal pockets of patients with dental caries and periodontal diseases. Green tea extract was prepared by aqueous extraction method and diluted from 50 to 1.56 mg/ml. Standard techniques of agar disk diffusion and broth microdilution assays were applied for qualitative and quantitative determinations of antibacterial activity of green tea extract on each isolates. Results: All clinical isolates of S. mutans (100%) were sensitive to green tea extract at concentrations 6.25, 12.5, 25, and 50 mg/ml producing inhibition zones ranging from 10 to 38 mm. All periodontopathic isolates (A. actinomycetemcomitans, n = 20, P. intermedia, n = 20, and P. gingivalis, n = 20) (100%) tested were sensitive to 12.5, 25, and 50 mg/ml of this extract. The minimal inhibitory concentration of green tea extract for S. mutans was 3.28 ± 0.7 mg/ml and for A. actinomycetemcomitans 6.25, for P. gingivalis and P. intermedia 12.5 mg/ml. Conclusions: Our findings showed that green tea extract exhibited strong antibacterial activity on S. mutans,A. actinomycetemcomitans,P. gingivalis and P. intermedia and therefore may be used in mouthwashes or dentifrices for prevention of dental caries and periodontal diseases.

Green tea as an effective antimicrobial for urinary tract infections caused by Escherichia coli

Background: Urinary tract infections (UTIs) are a very most common type of infection worldwide, and result in billions of dollars in medical care costs. Escherichia coli is the infective agent for 80–90% of all UTIs. Green tea, derived from leaves of the Camellia sinensis plant has been shown to have various potential health benefits (e.g., cardiovascular disease and cancer). The major beneficial components of green tea have been characterized, and are now known to be polyphenolic catechins. The main catechins in green tea are (-)-epicatechin-3-gallate, (-)-epigallocatechin (EGC), (-)-epicatechin, and (-)-epigallocatechin-3-gallate (EGCG). EGCG and EGC have been shown to have the greatest antimicrobial effects, but only EGC has been shown to be excreted in urine. Isolates of E. coli from UTIs collected between 2007 and 2008 were characterized for antimicrobial resistance to standard drugs. Then 80 of these isolates, representing a wide spectrum of antimicrobial susceptibility patterns, were selected for testing using an extract of green tea.Results: The concentrations of green tea extract tested were 0, 2.5, 3.0, 3.5, and 4.0 mg/ml. All of the strains tested, except one, had minimum inhibitory concentrations (MICs) of ≤4.0 mg/ml (99%), with 94% of the isolates having an MIC of ≤3.5 mg/ml, 76% of the isolates having an MIC of ≤3.0 mg/ml, 40% of the isolates having an MIC of ≤2.5 mg/ml. Two control strains varied in susceptibility, one having an MIC of ≤2.5 mg/ml,and the other having an MIC of ≤3.5 mg/ml.Conclusion: Since EGC has been shown to have antimicrobial effects on E. coli, and EGC has been shown to be excreted in the urine in a high enough concentration to potentially be effective as an antimicrobial; these MIC results suggest that ingesting green tea could have potential antimicrobial effects on UTIs caused by E. coli.

Preparation, properties and antioxidant activity of an active film from silver carp (Hypophthalmichthys molitrix) skin gelatin incorporated with green tea extract

An active film from silver carp skin gelatin incorporated with green tea extract (GTE) was developed. The effects of GTE concentrations including 0.3 and 0.7% (w/v) on the film properties were determined by measuring total polyphenolic content, antioxidant activity and physical properties. The findings of this study showed that the incorporation of GTE into gelatin films enhanced the total phenolic content, DPPH radical scavenging activity and reducing power. However, DPPH radical scavenging activity and reducing power decreased during storage. As regards the physical properties, higher GTE content incorporated into gelatin films revealed significantly higher tensile strength and lower elongation at break, water solubility and water vapor permeability, but no difference in thickness. Gelatin–GTE films exhibited lower light transmission in UV light, lower percent transmittance and higher transparency value compared to control film. Moreover, protein patterns of gelatin–GTE films had no changes. The thermal stability of gelatin–GTE films was improved and grew with the increasing concentration of GTE. FTIR spectra indicated that protein–polyphenol interactions were involved in the gelatin–GTE films. Smooth and homogeneous surface and compact-structure were observed in gelatin–GTE films. Thus, the addition of GTE into gelatin film improved the antioxidant activity and directly affected the properties most likely due to the interactions between gelatin and GTE.

녹차 추출물에 가압 침지한 오리알의 항산화 활성 변화

본 연구에서는 오리알에 녹차 추출물을 이용하여 가압침지처리를 함으로써 녹차의 기능성 성분을 침투시키고자 하였으며 가압침지 후 오리알의 성분변화와 항산화 활성의 변화를 연구하였다. 녹차의 활성성분을 함유하는 오리알을 제조하기 위해 녹차 10, 20, 30% 추출액에 오리알을 침지시켜 각각 1과 5MPa 조건에서 30분 동안 상온에서 가압하여 녹차의 catechin 성분들이 침투되도록 하였다. 대조구(0.17mg/100g)와 비교하여 오리알 난백의 EGCG 함량은 20mg/100 g(30% 녹차 추출물, 5MPa)으로 약 100배 이상 증가하였으며 침지시료의 농도와 압력이 증가할수록 EGCG 함량이 증가함을 알 수 있었다. 항산화 활성과 세포 보호 효과 및 ROS 제거 효과 모두 대조구보다 5MPa 조건에서 증가하는 것으로 나타났다. 본 연구 결과는 비교적 간단한 공정과 경제적인 방법으로 녹차의 EGCG 함량이 증가된 오리알을 제조하는 방법을 연구하고 그 활성을 증명함으로써 국내 오리알을 이용한 고부가가치 가공식품 개발과 오리알 의 소비촉진에 영향을 미칠 것으로 생각된다.

Changing oxidation in whey fat concentrate upon addition of green tea extract

Whey products with a high fat content are recognised to be more prone to oxidation compared to other dairy products, since whey fat is high in unsaturated phospholipids. Thus, strategies for inhibition of oxidation during processing and storage of high-fat whey products need to be developed. The purpose of the present study was to find an antioxidant which effectively inhibits oxidation in whey fat concentrate (WFC) during accelerated storage (60 °C) and to investigate the effect of the antioxidant on primary and secondary oxidation. The development of secondary lipid oxidation products was measured using a number of different antioxidants: Trolox (TRX), propyl gallate (PG), Grindox 1021 (GRX), green tea extract (GTE) and rosemary extract (RE). The development of the secondary lipid oxidation product hexanal was inhibited by all the tested antioxidants, and GTE was found to be the most efficient of the tested antioxidants. The effect of GTE concentrations (0, 50 and 500 μg/g whey solid) on oxidation was investigated further by measuring hydroperoxide and hexanal accumulation during accelerated storage (60 °C). Hydroperoxides were accumulated after a lag phase which was prolonged in the samples supplemented with 500 μg GTE/g whey solid. The accumulation of hexanal was highly reduced in the presence of GTE, and hexanal was accumulated without a lag phase. Thus, the results show that GTE effectively inhibits oxidation in WFC and suggest that GTE acts both as a chain-breaking antioxidant and as a transition metal ion chelator.

Green tea extract ameliorates reperfusion injury to rat livers after warm ischemia in a dose‐dependent manner

Polyphenolic constituents of green tea (Camellia sinensis) have been shown to be potent scavengers of reactive oxygen species (ROS). Thus, this study was designed to assess its effects after liver ischemia-reperfusion. Fasted Sprague-Dawley rats were gavaged with different concentrations of green tea extract (GTE) 2 h before 90 min of warm ischemia of the left lateral liver lobe (30% of liver). Controls were given the same volume of Ringer's solution. A preparation of pentobarbital sodium (intraperitoneal) and ketamine (intramuscular) was used for anesthesia. After reperfusion, transaminases, liver histology, hepatic microcirculation, and both phagocytosis of latex bead particles as well as the expression of tumor necrosis alpha (TNF-α) to index cellular activation were investigated. Furthermore, the expression of superoxide dismutase (Mn-SOD) was assessed. After 90 min of warm ischemia aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) increased dramatically to 1946 ± 272/3244 ± 757 U/L, 1680 ± 134/2080 ± 379 U/L, and 7857 ± 1851/2036 ± 1193 U/L at 2/6 h, respectively. GTE (200 mg/kgbody weight) significantly prevented this increase in a dose-dependent manner by 21-51% at 2 h and 29-34% at 6 h, respectively. Histology confirmed the protective effects while both TNF-α expression and phagocytosis of latex beads by Kupffer cells (KCs) were significantly reduced. GTE intake significantly increased the expression of manganese superoxide dismutase. In vivo microscopy revealed improved acinar and sinusoidal perfusion after GTE. Preconditioning with a single oral dose of GTE ameliorates ischemia-reperfusion injury in liver. Decreased cellular activation and improved microcirculation are the proposed mechanisms.

A stability study of green tea catechins during the biscuit making process

A green tea extract (GTE) was incorporated into biscuit as a source of tea catechins. The stability of tea catechins in the biscuit making process was studied. A method was developed for the separation and quantification of tea catechins in GTE, dough, and biscuit samples using a RP-HPLC system. GTEs at 150, 200, and 300mg per 100g of flour were formulated. The results obtained showed that green tea catechins were relatively stable in dough. The stability of (−)-EGCG and (−)-ECG was determined at an interval of every 2min during baking. Their stability decreased as the baking progressed and increased as the concentration of GTE was increased in the biscuit dough. The stability of (−)-EGCG also increased as pH of the dough was reduced and made less alkaline.

Physical properties and antioxidant activity of an active film from chitosan incorporated with green tea extract

An active film from chitosan incorporated with aqueous green tea extract (GTE) was developed. The effects of GTE concentrations including 2, 5, 10 and 20% (w/v) of green tea in the film-forming solution on the film properties were determined by measuring physical properties, total polyphenolic content and antioxidant activity of the active films. Fourier Transform Infrared (FTIR) spectrometry was carried out to observe the potential modifications of the chitosan films when incorporated with GTE. The results suggested that incorporation of GTE into chitosan films improved mechanical and water vapor barrier properties and enhanced polyphenolic content and antioxidant activity of the films. Changes in the FTIR spectra of the chitosan films were observed when GTE was incorporated, suggesting some interactions occurred between chitosan and the polyphenols from GTE. This study showed the benefits of incorporation of GTE into chitosan films and the potential for using the developed film as an active packaging.

Protective effects of green tea extracts on photoaging and photommunosuppression

This study aimed to investigate whether the sunscreen-containing 2-5% green tea extracts (GTEs) protect ultraviolet irradiation (UVR)-induced photoaging and photoimmunosuppression. Twenty volunteers were exposed to repetitive solar-simulated UVR (ssUVR) on the upper back at a dosage of 1.5 minimal erythema doses (MED) per day for four consecutive days. Thirty minutes before each UVR and 6, 24, and 48 h after the last UV exposure, the products containing vehicle, and 2-5% GTEs were applied onto five sites on the dorsal skin, respectively. The skin biopsies were obtained 72 h after the last UVR. The thickness of the stratum corneum and epidermis was measured under the microscope and the expression of cytokeratins (CK)-5/6, CK16, metalloproteinases (MMP)-2, MMP-9, and the CD1a(+) Langerhans cells (LCs) were determined using immunohistochemistry. Our results showed that UVR substantially induced cutaneous erythema, thickening of the epidermis, overexpression of CK5/6, CK16, MMP-2, MMP-9, and depletion of CD1a(+) LCs. The sunscreens containing different concentrations of GTEs conferred significant protection against the photoaging and photoimmunology-related biological events. Interestingly, the protective effects were not parallel to the concentrations of GTEs, with 2% and 3% GTEs showing the most efficacious photoprotection. GTEs-containing sunscreens have potential photoprotective effects on UVR-induced photoaging and photoimmunosuppression.

Green tea extract reduces induction of p53 and apoptosis in UVB‐irradiated human skin independent of transcriptional controls

Ultraviolet (UV) irradiation plays a pivotal role in human skin carcinongenesis. Preclinically, systemically and topically applied green tea extract (GTE) has shown reduction of UV-induced (i) erythema, (ii) DNA damage, (iii) formation of radical oxygen species and (iv) downregulation of numerous factors related to apoptosis, inflammation, differentiation and carcinogenesis. In humans, topical GTE has so far only been tested in limited studies, with usually very high GTE concentrations and over short periods of time. Both chemical stability of GTE and staining properties of highly concentrated green tea polyphenols limit the usability of highly concentrated green tea extracts in cosmetic products. The present study tested the utility of stabilized low-dose GTE as photochemopreventive agents under everyday conditions. We irradiated with up to 100 mJ/cm(2) of UVB light skin patches which were pretreated with either OM24-containing lotion or a placebo lotion. Biopsies were taken from both irradiated and un-irradiated skin for both immunohistochemistry and DNA microarray analysis. We found that while OM24 treatment did not significantly affect UV-induced erythema and thymidine dimer formation, OM24 treatment significantly reduced UV-induced p53 expression in keratinocytes. We also found that OM24 treatment significantly reduced the number of apoptotic keratinocytes (sunburn cells and TUNEL-positive cells). Carefully controlled DNA microarray analyses showed that OM24 treatment does not induce off-target changes in gene expression, reducing the likelihood of unwanted side-effects. Topical GTE (OM24) reduces UVB-mediated epithelial damage already at low, cosmetically usable concentrations, without tachyphylaxis over 5 weeks, suggesting GTE as suitable everyday photochemopreventive agents.

Green tea extract and its major component epigallocatechin gallate inhibits hepatitis B virus in vitro

Hepatitis B virus (HBV) infection is endemic in Asia and causes major public health problems worldwide. Present treatment strategies for HBV infections are not satisfactory and the clinical limitation of current antiviral drugs for HBV, such as lamivudine, is causing rapid emergence of drug-resistant viral strains during the prolonged therapeutic treatment. In this research, the efficacy of a natural green tea extract (GTE) against HBV in a stably expressed HBV cell line HepG2-N10 is examined. The expression of viral antigens, HBsAg and HBeAg, were determined by using enzyme linked immuno-absorbent assay (ELISA). Quantitative real-time-PCR (Q-PCR) was used for the determination of extracellular HBV DNA and intracellular replicative intermediates and nuclear covalent closed circular DNA (cccDNA). HBV mRNAs were also analyzed by reverse transcription PCR (RT-PCR). Results showed that the 50% effective concentration (EC 50) of GTE on HBsAg, HBeAg, extracellular HBV DNA and intracellular HBV DNA were 5.02, 5.681, 19.81, and 10.76 μg/ml, respectively. While the concentration of GTE with the inhibition percentage of 50% on proliferating cells (CC 50) was 171.8 μg/ml. Similar analysis of the principal component of GTE, epigallocatechin gallate (EGCG), revealed it has relative weaker efficacy compared to GTE.

Green Tea Extract and (−)-Epigallocatechin-3-Gallate Inhibit Mast Cell-Stimulated Type I Collagen Expression in Keloid Fibroblasts via Blocking PI-3K/Akt Signaling Pathways

Keloid, a chronic fibro-proliferative disease, exhibits distinctive histological features characterized by an abundant extracellular matrix stroma, a local infiltration of inflammatory cells including mast cells (MCs), and a milieu of enriched cytokines. Previous studies have demonstrated that co-culture with MCs stimulate type I collagen synthesis in fibroblasts, but the signaling mechanisms remain largely unknown. In this study, we investigated the signaling pathways involved in MC-stimulated type I collagen synthesis and the effects of green tea extract (GTE) and its major catechin, (-)-epigallocatechin-3-gallate (EGCG), on collagen homeostasis in keloid fibroblasts. Our results showed that MCs significantly stimulated type I collagen expression in keloid fibroblasts, and the upregulation of type I collagen was significantly attenuated by blockade of phosphatidylinositol-3-kinase (PI-3K), mammalian target of rapamycin (mTOR), and p38 MAPK signaling pathways, but not by blockade of ERK1/2 pathway. Furthermore, GTE and EGCG dramatically inhibited type I collagen production possibly by interfering with the PI-3K/Akt/mTOR signaling pathway. Our findings suggest that interaction between MCs and keloid fibroblasts may contribute to excessive collagen accumulation in keloids and imply a therapeutic potential of green tea for the intervention and prevention of keloids and other fibrotic diseases.

Green Tea Extract Blocks the TRIF‐Mediated TLR4 Signaling Cascade

Green tea has long been known for its efficacy in immune diseases however only recently have we examined the mechanisms of its effects. Studies have shown that green tea has a profound effect on LPS induced TLR4 signaling in peritoneal macrophages in mice. The present study investigated the levels of several chemokines upregulated through the TRIF adaptor protein during TLR4 activation. Peritoneal macrophages from C57BL/6 mice were treated with various concentrations of green tea extract (GTE; 1μg/ml, 10μg/ml, 100μg/ml) and LPS (100ng/ml) for 24 hours. Expression of B7.1/CD80, B7.2/CD86 and MHCII were detected by flow cytometry. Expression of IP10, IL1β, TNFα and CCL5 (RANTES) were quantified by ELISA. The data demonstrates that GTE downregulates TRIF dependent chemokines after LPS-induced TLR4 activation. Indeed, GTE reduced chemokine and co-stimulatory molecule expression from murine peritoneal macrophages to control levels. IP10 was increased to 1.5 pg/ml by LPS and GTE reduced the levels back to control (undetectable), in a dose dependent manner. Similarly, IL1β expression (control - undetectable, LPS - 8.7 pg/ml, LPS + GTE – undetectable) and CCL5 expression (control – 104.5, LPS - 550 pg/ml, LPS+ GTE – 47.7 pg/ml) were significantly reduced. Further, flow cytometry demonstrated that GTE inhibited LPS induced expression of B7 molecules and MHCII. The clinical relevance of this study is its potential impact in reducing allograft rejection. The release of CCL5 by T cells and both IL1β and TNFα from peritoneal macrophages is the signature of late graft rejection. If GTE can supplement, reduce or eliminate the need for immunosuppressants in transplantation, fewer transplant patients will suffer late rejection.

Toxicity of green tea extracts and their constituents in rat hepatocytes in primary culture

Recent reports on sporadic cases of liver disorders (acute hepatitis, icterus, hepatocellular necrosis) after ingestion of dietary supplements based on hydro-alcoholic extracts from green tea leaves led to restrictions of the marketing of such products in certain countries of the EU. Since green tea is considered to exert a number of beneficial health effects, and, therefore, green tea products are widely used as dietary supplements, we were interested in the possible mechanism of hepatotoxicity of green tea extracts and in the components involved in such effects. Seven hours after seeding on collagen, rat hepatocytes in primary culture were treated with various hydro-alcoholic green tea extracts (two different native 80% ethanolic dry extracts and an 80% ethanolic dry extract cleared from lipophilic compounds). Cells were washed, and reduction of resazurin, used as a viability parameter monitoring intact mitochondrial function, was determined. It was found that all seven green tea extracts examined enhanced resazurin reduction significantly at a concentration range of 100–500μg/ml medium, while a significant decrease was observed at 1–3mg/ml medium. Decreased levels were concomitant with abundant necrosis as observed by microscopic inspection of the cultures and with increased leakage of lactate dehydrogenase activity from the cells. In a separate series of experiments, the green tea constituents (−)-epicatechin, (−)-epigallocatechin-3-gallate, caffeine and theanine were tested at concentrations reflecting their levels in a typical green tea extract. Synthetic (+)-epigallocatechin (200μM) was used for comparison. Cytotoxicity was found with (−)-epigallocatechin-3-gallate only. The concomitant addition of 0.25mM ascorbate/0.05mM α-tocopherol had no influence on cytotoxicity. In conclusion, our results suggest that high concentrations of green tea extract can exert acute toxicity in rat liver cells. (−)-Epigallocatechin-3-gallate seems to be a key constituent responsible for this effect. The relatively low bioavailability of catechins reported after oral exposure to green tea argues, however, against a causal role of these constituents in the reported liver disorders.