Anti-Influenza with Green Tea Catechins: A Systematic Review and Meta-Analysis

Influenza is one of the most serious respiratory viral infections worldwide. Although several studies have reported that green tea catechins (GTCs) might prevent influenza virus infection, this remains controversial. We performed a systematic review and meta-analysis of eight studies with 5048 participants that examined the effect of GTC administration on influenza prevention. In a random-effects meta-analysis of five RCTs, 884 participants treated with GTCs showed statistically significant effects on the prevention of influenza infection compared to the control group (risk ratio (RR) 0.67, 95% CIs 0.51–0.89, p = 0.005) without evidence of heterogeneity (I² = 0%, p = 0.629). Similarly, in three cohort studies with 2223 participants treated with GTCs, there were also statistically significant effects (RR 0.52, 95% CIs 0.35–0.77, p = 0.001) with very low evidence of heterogeneity (I² = 3%, p = 0.358). Additionally, the overall effect in the subgroup analysis of gargling and orally ingested items (taking capsules and drinking) showed a pooled RR of 0.62 (95% CIs 0.49–0.77, p = 0.003) without heterogeneity (I² = 0%, p = 0.554). There were no obvious publication biases (Egger’s test (p = 0.138) and Begg’s test (p = 0.103)). Our analysis suggests that green tea consumption is effective in the prophylaxis of influenza infections. To confirm the findings before implementation, longitudinal clinical trials with specific doses of green tea consumption are warranted.     

HPLC法测定茶叶中儿茶素及咖啡碱

以绿茶为样本,以GB/T 8305–1987水浸出方式作为样品的提取方法,使用C18色谱柱(150 mm×4.6mm,5μm),以A相(超纯水)、B相(N–N二甲基甲酰胺︰甲醇︰冰乙酸=40︰2︰1.5)为流动相,在最佳梯度洗脱条件下对8种组分进行分离,紫外检测器检测,检测波长为278 nm,外标法定量。没食子酸、咖啡碱、表没食子儿茶素、儿茶素、表儿茶素、表没食子儿茶素没食子酸酯、没食子基儿茶素没食子酸酯和表儿茶素没食子酸酯8种组分的进样质量分别在0.0243~0.1456,0.2549~1.5296,0.2027~1.2164,0.0182~0.1102,0.1606~0.9634,1.0004~6.0024,0.018 2~0.109 0,0.229 6~1.377 4μg范围内与色谱峰面积的线性关系良好(r为0.991 0~0.999 9);加标回收率为98.60%~100.17%,RSD均小于0.48%(n=3)。对样品进行6次重复测定,与标准方法相比,8种组分测定结果的相对偏差为0.47%~5.55%。该方法简便、快速、准确、稳定、重复性好,可用于茶叶中8种成分的定量分析。     

Green Tea Suppresses Brain Aging

Epidemiological studies have demonstrated that the intake of green tea is effective in reducing the risk of dementia. The most important component of green tea is epigallocatechin gallate (EGCG). Both EGCG and epigallocatechin (EGC) have been suggested to cross the blood–brain barrier to reach the brain parenchyma, but EGCG has been found to be more effective than EGC in promoting neuronal differentiation. It has also been suggested that the products of EGCG decomposition by the intestinal microbiota promote the differentiation of nerve cells and that both EGCG and its degradation products act on nerve cells with a time lag. On the other hand, the free amino acids theanine and arginine contained in green tea have stress-reducing effects. While long-term stress accelerates the aging of the brain, theanine and arginine suppress the aging of the brain due to their anti-stress effect. Since this effect is counteracted by EGCG and caffeine, the ratios between these green tea components are important for the anti-stress action. In this review, we describe how green tea suppresses brain aging, through the activation of nerve cells by both EGCG and its degradation products, and the reductions in stress achieved by theanine and arginine.     

Green Tea Catechins Attenuate Neurodegenerative Diseases and Cognitive Deficits

Neurodegenerative diseases exert an overwhelming socioeconomic burden all around the globe. They are mainly characterized by modified protein accumulation that might trigger various biological responses, including oxidative stress, inflammation, regulation of signaling pathways, and excitotoxicity. These disorders have been widely studied during the last decade in the hopes of developing symptom-oriented therapeutics. However, no definitive cure has yet been discovered. Tea is one of the world’s most popular beverages. The same plant, Camellia Sinensis (L.).O. Kuntze, is used to make green, black, and oolong teas. Green tea has been most thoroughly studied because of its anti-cancer, anti-obesity, antidiabetic, anti-inflammatory, and neuroprotective properties. The beneficial effect of consumption of tea on neurodegenerative disorders has been reported in several human interventional and observational studies. The polyphenolic compounds found in green tea, known as catechins, have been demonstrated to have many therapeutic effects. They can help in preventing and, somehow, treating neurodegenerative diseases. Catechins show anti-inflammatory as well as antioxidant effects via blocking cytokines’ excessive production and inflammatory pathways, as well as chelating metal ions and free radical scavenging. They may inhibit tau protein phosphorylation, amyloid beta aggregation, and release of apoptotic proteins. They can also lower alpha-synuclein levels and boost dopamine levels. All these factors have the potential to affect neurodegenerative disorders. This review will examine catechins’ neuroprotective effects by highlighting their biological, pharmacological, antioxidant, and metal chelation abilities, with a focus on their ability to activate diverse cellular pathways in the brain. This review also points out the mechanisms of catechins in various neurodegenerative and cognitive diseases, including Alzheimer’s, Parkinson’s, multiple sclerosis, and cognitive deficit.     

Health Effects of Soy Isoflavones and Green Tea Catechins on Cancer and Cardiovascular Diseases Based on Urinary Biomarker Levels

Plant polyphenols have various health effects. Genistein, which is abundant in soybeans, and epigallocatechin-3-gallate, which is abundant in green tea, are major flavonoids, a subclass group of polyphenols. Several epidemiological studies have shown that these flavonoids have beneficial effects against cancer and cardiovascular diseases. However, other studies did not show such effects. Several confounding factors, including recall bias, are related to these inconsistent findings, and the determination of metabolites in the urine may be useful in reducing the number of confounding factors. Equipment, which can be used by research participants to collect samples from a portion of voided urine within 24 h without the help of medical workers, has been developed for epidemiological investigations. Previous studies, in which flavonoid metabolites in these urine samples were measured, revealed that soy intake was correlated with a reduced risk of certain types of cancer and cardiovascular diseases worldwide. Although soybeans and green tea consumption may have protective effects against cancer and cardiovascular diseases, further clinical studies that consider different confounding factors are required to provide evidence for the actual impact of dietary flavonoids on human diseases, including cancer and cardiovascular diseases. One possible mechanism involved is discussed in relation to the downregulation of reactive oxygen species and the upregulation of 5′-adenosine monophosphate-activated protein kinase elicited by these flavonoids.     

Health Benefits and Chemical Composition of Matcha Green Tea: A Review

Japanese matcha is a type of powdered green tea, grown in a traditional way. Shading of the plants during the growth period enhances the processes of synthesis and accumulation of biologically active compounds, including theanine, caffeine, chlorophyll and various types of catechins. Green tea contains four main catechins, i.e., (−)-epicatechin (EC), (−)-epicatechin-3-gallate (ECG), (−)-epigallocatechin (EGC) and (−)-epigallocatechin-3-gallate (EGCG), of which the latter is the most active and abundant and matcha is their best condensed source. Due to its unique chemical composition and prized flavour, which sets it apart from other tea beverages, it is considered the highest quality tea. Its health-promoting properties are attributed to the high content of antioxidant and anti-inflammatory substances. Studies confirming the high antioxidant potential of tea beverages claim that it originates from the considerable content of catechins, a type of phenolic compound with beneficial effects on human health. Due to its potential for preventing many diseases and supporting cognitive function, regular consumption of matcha may have a positive effect on both physical and mental health. The aim of this review was to compile the health benefits of matcha tea. It is the first such review to be undertaken, and presents its main bioactive compounds in a systematic manner.     

Effect of Ferrous Ion on Heat-Induced Aroma Deterioration of Green Tea Infusion

Aroma deterioration is one of the biggest problems in processing tea beverages. The aroma of tea infusion deteriorates fast during heat sterilization and the presence of ferrous ion (Fe²⁺) aggravates it. The underlying mechanism remains unveiled. In this study, Fe²⁺ was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe²⁺-mediated aroma deterioration. By enhancing the degradation of catechins, Fe²⁺ dramatically increased the production of hydrogen peroxide (H₂O₂). Fe²⁺ and H₂O₂ together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe²⁺ enhanced the loss of green/grassy volatiles and promoted the formation of new volatiles with diversified aroma characteristics, resulting in a dull scent of green tea infusion. Our results revealed how Fe²⁺ induced aroma deterioration of green tea infusion with heat treatment and could help guide tea producers in attenuating the aroma deterioration of tea infusion during processing.     

Electroanalytical Sensing of Green Tea Anticarcinogenic Catechin Compounds: Epigallocatechin Gallate and Epigallocatechin

A novel electroanalytical methodology for the sensing of anticarcinogenic catechin compounds epigallocatechin gallate (EGCG) and epigallocatechin (EGC) is presented. The protocol is based on the electrochemical oxidation of aminophenol in aqueous solutions, where the quinoneimine oxidation product chemically reacts with the EGCG or EGC compounds resulting in consumption of quinoneimine and consequently results in a reduction in the magnitude of the quinoneimine reduction wave, which is found to provide an analytical signal from which to indirectly detect EGCG and/or EGC.     

Isolation and Purification of a Novel Long－chain Acyl Catechin from Lipophilic Tea Polyphenols

Llpophilic tea polyphenols (LTP) was prepared by esterification of green tea polyphenols (GTP) with hexadecanoyl chloride. A novel long-chaln acyl catechin was isolated and purified from LTP by high-speed countercurrent chromatography (HSCCC).Its molecular structure was elucidated as epigallocatechin-3-O-gallate-4‘-O-hexadecanate by elemental analysis, IR, MS and ^1H NMR spectra.     

Advances in Nanodelivery of Green Tea Catechins to Enhance the Anticancer Activity

Cancer is one of the leading causes of death globally. A variety of phenolic compounds display preventative and therapeutic effects against cancers. Green teas are rich in phenolics. Catechins are the most dominant phenolic component in green teas. Studies have shown that catechins have anticancer activity in various cancer models. The anticancer activity of catechins, however, may be compromised due to their low oral bioavailability. Nanodelivery emerges as a promising way to improve the oral bioavailability and anticancer activity of catechins. Research in this area has been actively conducted in recent decades. This review provides the molecular mechanisms of the anticancer effects of catechins, the factors that limit the oral bioavailability of catechins, and the latest advances of delivering catechins using nanodelivery systems through different routes to enhance their anticancer activity.     

高效液相色谱法测定绿茶中茶多酚及咖啡因

应用高效液相色谱法测定绿茶中没食子酸(GA)、咖啡因(CAF)及5种儿茶素类化合物,包括儿茶素(C)、表儿茶素(EC)、表没食子儿茶素没食子酸酯(EGCG)、表儿茶素没食子酸酯(ECG)、没食子儿茶素没食子酸酯(GCG)。对国家标准方法GB/T 8313-2008中流动相组成进行了调整,用0.5%乙酸代替2%的乙酸,在AT.Lichrom ODS色谱柱(4.6mm×250mm,5μm)上进行分离,流量为1.0mL.min-1,在波长278nm处进行紫外检测。7种组分在40min内达到完全分离。7种组分的质量浓度分别在一定的范围内与其峰面积呈线性关系。方法用于绿茶的分析,7种组分的加标回收率在96.0%～102.8%之间。     

Green,Black and Rooibos Tea Inhibit Prostaglandin E2 Formation in Human Monocytes by Inhibiting Expression of Enzymes in the Prostaglandin E2 Pathway

The formation of prostaglandin E2 (PGE2) is associated with adverse inflammatory effects. However, long-term treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) comes with risk of severe side effects. Therefore, alternative ways to inhibit PGE2 are warranted. We have investigated the effects of tea extracts and the polyphenols epigallocatechin gallate (EGCG) and quercetin on PGE2 formation, determined by immunoassay, and protein expression, determined by immunoblotting, of cytosolic phospholipase A2 (cPLA2), cyclooxygenase 2 (COX-2) and microsomal PGE synthase-1 (mPGES-1) in human monocytes. Green and black tea extracts, and with a lower potency, Rooibos tea extract, inhibited lipopolysaccharide (LPS) and calcium ionophore-induced PGE2 formation. In addition, all tea extracts inhibited the LPS-induced expression of mPGES-1, and the green and black tea extracts also inhibited, to a lesser extent, COX-2 expression. The tea extracts only marginally reduced cPLA2 expression and had no effect on COX-1 expression. EGCG, present in green and black tea, and quercetin, present in all three teas, also inhibited PGE2 formation and expression of mPGES-1, COX-2 and cPLA2. Cell-based and cell-free assays were also performed to evaluate direct effects on the enzymatic activity of COX and PGE synthases. Mainly, the cell-free assay demonstrated partial inhibition by the tea extracts and polyphenols. However, the inhibition required higher doses compared to the effects demonstrated on protein expression. In conclusion, green and black tea, and to a lesser extent Rooibos tea, are potent inhibitors of PGE2 formation in human monocytes, and mediate their effects by inhibiting the expression of the enzymes responsible for PGE2 formation, especially mPGES-1.     

Speciation of Manganese in Tea Leaves and Tea Infusions

Abstract

A speciation scheme was developed for identification of the chemical forms of manganese in tea leaves and tea infusions. The range of manganese in five different groups of tea leaves was found to be 1107 – 2205 μg/g on a dry basis. It was noted that 30.0% of Mn was passed into the water that was present in the form of Mn(II), and also 2.5% of Mn was found as the total organic bound fraction and passed into the various solvents.     

Solid-state NMR analysis of the orientation and dynamics of epigallocatechin gallate, a green tea polyphenol, incorporated into lipid bilayers

Catechins are the principle polyphenolic compounds in green tea; the four major compounds identified are epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg) and epigallocatechin gallate (EGCg). Tea catechins tend to attach externally to their targets, such as viral envelopes, cell membranes, or the surface of low-density lipoproteins. In order to further our understanding of the molecular mobility of these compounds in cells, we examined the interaction of tea catechins with lipid membranes using solid-state NMR techniques. Our previous work indicated that the EGCg molecule is incorporated into lipid bilayers in a unique orientation. However, the detailed configuration, orientation, and dynamics of EGCg in lipid bilayers have not been well-characterized. Here, we investigated the orientation and dynamics of EGCg incorporated into multi-lamellar vesicles (MLVs) and bicelles using solid-state NMR spectroscopy.     

二安替比林（3,4—二甲氧基）苯基甲烷光度法测定茶叶中锰

在碱性介质中，加热时空气氧化Ｍｎ为Ｍｎ，Ｍｎ与二安替比林苯基甲烷反应生成橙色产物，吐温２０和乳酸起到协同增敏作用，λｍａｘ＝４６０ｎｍ，ε＝７．８×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１，锰量在０－１２μｇ／２５ｍｌ范围内符合比尔定律。     

Identification and Quantification of Anthocyanin and Catechin Compounds in Purple Tea Leaves and Flakes

Tea is the first most popular beverage worldwide and is available in several selections such as black (fully oxidized), Oolong (partially oxidized) and green (non-oxidized), in addition to purple tea, an emerging variety derived from the same tea plant (Camellia sinensis). This study investigated purple tea leaves (non-oxidized) and flakes (water extractable) to thoroughly identify their composition of anthocyanins and catechins and to study the effect of a water extraction process on their compositional properties in comparison with green tea. Anthocyanin and catechin compounds were separated and quantified using UPLC, and their identity was confirmed using LC-MS/MS in positive and negative ionization modes. Delphinidin was the principal anthocyaninidin in purple tea, while cyanidin came in second. The major anthocyanin pigments in purple tea were delphinidin-coumaroyl-hexoside followed by delphinidin-3-galactoside and cyanidin-coumaroyl-hexoside. The water extraction process resulted in substantial reductions in anthocyanins in purple tea flakes. There were no anthocyanin compounds detected in green tea samples. Both purple and green tea types were rich in catechins, with green tea containing higher concentrations than purple tea. The main catechin in purple or green tea was epigallocatechin gallate (EGCG) followed by either epicatechin gallate (ECG) or epigallocatechin (EGC), subject to tea type. The extraction process increased the concentration of catechins in both purple and green tea flakes. The results suggest that purple tea holds promise in making healthy brews, natural colorants and antioxidants and/or functional ingredients for beverages, cosmetics and healthcare industries due to its high content of anthocyanins and catechins.     

Antiviral Effects of Green Tea EGCG and Its Potential Application against COVID-19

(–)-Epigallocatechin-3-O-gallate (EGCG), the most abundant component of catechins in tea (Camellia sinensis (L.) O. Kuntze), plays a role against viruses through inhibiting virus invasiveness, restraining gene expression and replication. In this paper, the antiviral effects of EGCG on various viruses, including DNA virus, RNA virus, coronavirus, enterovirus and arbovirus, were reviewed. Meanwhile, the antiviral effects of the EGCG epi-isomer counterpart (+)-gallocatechin-3-O-gallate (GCG) were also discussed.     

茶叶及茶多酚中儿茶素的高效液相色谱分析方法研究

 筛选出HypersilBDSC18和ZorbaxSBC18两种适合同时分离茶叶和茶多酚中 7种儿茶素和咖啡因的反相柱。采用甲醇 水 醋酸 (或三氟醋酸 )作流动相 ,分别以等强度洗脱和梯度洗脱 (均在 30min内 )分离测定了我国 6种不同产地茶叶样品和 3种茶多酚样品中 7种儿茶素的含量。考察了 7种儿茶素和咖啡因的保留值与流动相组成及柱温的关系 ,优化了色谱条件及样品前处理方法。用电喷雾电离质谱 (ESI MS)定性确认没食子儿茶素没食子酸酯(GCG)和儿茶素没食子酸酯 (CG)两组分 ,并用高效液相色谱制备两对照品用于定量分析。     

绿茶儿茶素的最新合成进展

简要介绍了绿茶儿茶素的组成及活性, 重点综述了有关儿茶素及其衍生物合成研究的最新进展.     

Significant Inactivation of SARS-CoV-2 In Vitro by a Green Tea Catechin,a Catechin-Derivative,and Black Tea Galloylated Theaflavins

Potential effects of tea and its constituents on SARS-CoV-2 infection were assessed in vitro. Infectivity of SARS-CoV-2 was decreased to 1/100 to undetectable levels after a treatment with black tea, green tea, roasted green tea, or oolong tea for 1 min. An addition of (−) epigallocatechin gallate (EGCG) significantly inactivated SARS-CoV-2, while the same concentration of theasinensin A (TSA) and galloylated theaflavins including theaflavin 3,3′-di-O-gallate (TFDG) had more remarkable anti-viral activities. EGCG, TSA, and TFDG at 1 mM, 40 µM, and 60 µM, respectively, which are comparable to the concentrations of these compounds in tea beverages, significantly reduced infectivity of the virus, viral RNA replication in cells, and secondary virus production from the cells. EGCG, TSA, and TFDG significantly inhibited interaction between recombinant ACE2 and RBD of S protein. These results suggest potential usefulness of tea in prevention of person-to-person transmission of the novel coronavirus.