Interaction of Tea Catechins with Lipid Bilayers Investigated by a Quartz-Crystal Microbalance Analysis

The quartz-crystal microbalance (QCM) technique was applied to investigate the interaction of tea catechins with lipid bilayers. The association constants obtained from the frequency changes of QCM revealed that (?)epicatechin gallate and (?)epigallocatechin gallate interacted with 1,2-dimyristoyl-sn-glycero-3-phosphocholine ca. 1000 times more strongly than (?)epicatechin and (?)epigallocatechin. The results exhibited good correlation with the strength of biological activity.     

Relationship between the anti-hemolysin activity and the structure of catechins and theaflavins

We examined the corresponding isomers of catechins and theaflavins for anti-hemolysin activities against Staphylococcus aureus alpha-toxin and Vibrio cholerae O1 hemolysin. Catechins and theaflavins showed anti-hemolysin activities in a dose-dependent manner. Among the catechins tested, (-)catechin gallate, (-)epicatechin gallate and (-)epigallocatechin gallate having galloyl groups in their molecules showed more potent anti-hemolysin activities against both toxins. On the other hand, free catechins, i. e. (-)catechin, (-)gallocatechin, (-) epicatechin and (-)epigallocatechin had low anti-hemolysin activities against alpha-toxin. Although (-)catechin or (-)gallocatechin had no effect on cholera hemolysin, (-) epicatechin and (-)epigallocatechin were slightly inhibitory. Among dextrocatechins, (+) epicatechin and (+)epigallocatechin proved to be more effective than (+)catechin and (+) gallocatechin. The anti-hemolysin activities of theaflavins against alpha-toxin and cholera hemolysin were dependent on the number of the galloyl group in their structure. These results suggest that the tertiary structure of the catechin or theaflavin and the active site of hemolysin, that affects the interaction between them, plays an important role in the anti-hemolysin activity.     

Interaction of Tea Catechins with Lipid Bilayers Investigated with Liposome Systems

Interaction of tea catechins with lipid bilayers was investigated with liposome systems, which enabled us to separate liposomes from the external medium by centrifugation. We found that epicatechin gallate had the highest affinity for lipid bilayers, followed by epigallocatechin gallate, epicatechin, and epigallocatechin. Epicatechin gallate and epigallocatechin gallate in the surface of lipid bilayer perturbed the membrane structure.     

Interaction of tea catechins with lipid bilayers investigated with liposome systems

Interaction of tea catechins with lipid bilayers was investigated with liposome systems, which enabled us to separate liposomes from the external medium by centrifugation. We found that epicatechin gallate had the highest affinity for lipid bilayers, followed by epigallocatechin gallate, epicatechin, and epigallocatechin. Epicatechin gallate and epigallocatechin gallate in the surface of lipid bilayer perturbed the membrane structure.     

Affinity of polyphenols for lipid bilayers

Interaction of tea catechins with lipid bilayers has been investigated with liposome systems. Epicatechin gallate had the highest affinity for lipid bilayers, followed by epigallocatechin gallate, epicatechin, and epigallocatechin. Epicatechin gallate and epigallocatechin gallate in the surface of lipid bilayer perturbed the membrane structure.     

Determination of catechins in human urine subsequent to tea ingestion by high-performance liquid chromatography with electrochemical detection

The title determination was conducted by HPLC with electrochemical detection using an ODS column and a mobile phase of acetonitrile: 0.1 M phosphate buffer (pH 2.5) (15:85, v/v). The eight catechins, gallocatechin (GC), epigallocatechin (EGC), catechin (C), epicatechin (EC), epigallocatechin gallate (EGCg), gallocatechin gallate (GCg), epicatechin gallate (ECg), and catechin gallate (Cg), were detected at 0.6 V vs Ag/AgCl. Good linear relationships between current and amount were noted for 0.5-250 pmol of each catechin, with a correlation coefficient of 0.999 in each case. The detection limit for any one was 0.5 pmol (signal to noise ratio, S/N = 3). After the ingestion of 340 ml canned green tea, GC, EGC, C, and EC, mostly in conjugated form, were determined in urine samples. Conjugated catechins were hydrolyzed by enzymes using sulfatase and beta-glucuronidase. The time courses of the above four catechins showed a maxima at 1-3 h after tea ingestion. (+), (-)-EC and (+), (-)-C were present in canned tea.     

Enhancement of phagocytic activity of macrophage-like cells by pyrogallol-type green tea polyphenols through caspase signaling pathways

We investigated the phagocytosis-enhancing activity of green tea polyphenols, such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC) catechin (+C) and strictinin, using VD3-differentiated HL60 cells. EGCG, EGC, ECG and strictinin, but not EC and +C, increased the phagocytic activity of macrophage-like cells, and a caspase inhibitor significantly inhibited phagocytic activities. These results suggest that the pyrogallol-type structure in green tea polyphenols may be important for enhancement of the phagocytic activity through caspase signaling pathways.     

Effects of catechin concentration on the formation of black tea polyphenols during in vitro oxidation

An in vitro model fermentation system, containing purified catechins and partially purified polyphenol oxidase (EC 1.14.81.1) from green tea shoots, has been used to determine the efrect of catechin mixtures of different concentration and proportions on the formation of theaflavin and thearubigin. Increases in total catechin concentration, 25% above that typical in green tea shoots of Malawi-grown bushes, inhibited polyphenol oxidase activity and, consequently, depressed theaflavin levels. Individual or combined concentrations of epicatechin gallate and epigallocatechin gallate in excess of 110 mM were shown to be responsible for enzyme inhibition, whereas epicatechin and epigallocatechin had no effect. Fermentation of a catechin mixture, containing the four major catechins, epicatechin, epigallocatechin, epigallocatechin gallate and epicatechin gallate, at equal individual concentrations (55 mM), produced, after 3O min, total theaflavin levels 68% higher and thearubigin levels only 25% higher than those from a standard catechin mixture fermented under similar conditions. Continued fermentation of this mixture produced no further theaflavin, but the thearubigin fraction increased significantly, due to subsequent oxidation of the excess of simple catechins. A new catechin mixture was, therefore, calculated to give a similar level of theaflavin to that of the previous mixture without leaving an excess of unoxidized simple catechins. The catechin proportions and concentrations of the latter mixture agree well with those of the green shoots of quality Kenyan teas or similar quality Malawi teas grown during the dry cold season. The results indicate that a high ratio of simple to gallocatechins will facilitate a high theaflavin-thearubigin ratio in black tea.     

Adsorption affinity of tea catechins onto polymeric resins: Interpretation from molecular orbital theory

Adsorption of certain tea catechins such as (+) catechin (C), (−) epicatechin (EC), (+) gallocatechin (GC), (−) epigallocatechin (EGC), (+) catechin gallate (CG), (−) epicatechin gallate (ECG), (+) gallocatechin gallate (GCG), and (−) epigallocatechin gallate (EGCG) have been studied using three types of polymeric resins as adsorbents. Adsorption affinity expressed as the slope of the linear region of the isotherm for a solute is found to be different for different adsorbents, and this difference can be interpreted from the chemical nature of the sorbents. Molecular interactions on polymeric resins have been studied based on molecular orbital theory. Electronic states of adsorbent and adsorbate were calculated using the semiempirical molecular orbital (MO) method from which energy of adsorption in aqueous solution was estimated. The adsorptive interaction on the polymeric resins computed on the basis of frontier orbital theory seems to correlate well with the experimentally measured adsorption affinity and enthalpy.     

An analytical survey of the polyphenols of seeds of varieties of grape (Vitis vinifera) cultivated in Greece: implications for exploitation as a source of value-added phytochemicals

Seed samples from 12 white and 25 red international and Hellenic native grape varieties (Vitis vinifera) were screened for their polyphenolic composition. The polyphenols determined were mainly of low molecular weight, including gallic acid, catechin, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate and the procyanidins B1 and B2. Average values of total content for white and red varieties (376 and 388 mg/100 g seeds, respectively) were very similar. Comparable results were observed with respect to the individual polyphenol content with seeds from red varieties being, in general, slightly richer. The predominant flavanol monomer in white and red varieties was catechin (which accounted for 50.5 and 49.3%, respectively, of the total content), whilst gallic acid and epigallocatechin were the constituents showing the lowest content, respectively. The data obtained are discussed with regard to the exploitation of grape seeds as a low-cost source of value-added phytochemicals.     

人工接种冠突散囊菌对白茶主要呈味物质的影响

本文为了排除其他微生物的干扰,首次以人工接种的方式研究了冠突散囊菌Eurotium cristatum对白茶主要呈味物质的作用。采用高效液相色谱、分光光度计等方法,分析表明冠突散囊菌能够显著降低白茶中呈苦涩味的表没食子儿茶素没食子酸酯（EGCG）和表儿茶素没食子酸酯（ECG）,并提高表没食子儿茶素（EGC）、Asp、His、咖啡碱和山奈酚的含量;灭菌压制的过程中EGCG可能异构化成为更稳定的没食子儿茶素没食子酸酯（GCG）,且二者以相近的含量共存。冠突散囊菌可以降低人工发花白茶饼中呈苦涩味的化合物含量,从而达到减少白茶饼苦涩味的效果;灭菌压制过程也能够降低白茶饼的苦涩味物质的含量。“发花”处理为白茶带来了新的风味,可以丰富白茶产品种类,同时为促进粗老原料白茶的综合利用提供新思路。     

Epigallocatechin gallate increase the prostacyclin production of bovine aortic endothelial cells

We describe the effect of (-) epigallocatechin gallate (EGCg), one of catechins known in tea, on the prostacyclin (PGI) production by bovine aortic endothelial cells. The amounts of 6-keto-PGF(1alpha) and Delta(17)-6-keto-PGF(1alpha), stable metabolites of PGI(2) and PGI(3), released in culture medium were measured using gas chromatography/selected ion monitoring (GC/SIM). The prostacyclin production of endothelial cells was increased by EGCg in a dose- and time-dependent manner. The effect by EGCg was stronger than any other catechins (catechin, epicatechin, epigallocatechin, and epicatechin gallate). When endothelial cells incubated with EGCg and arachidonic acid (AA) or eicosapentaenoic acid (EPA), PGI(2), and PGI(3) production were increased greater than those incubated with AA or EPA alone. Furthermore, gallic acid, that also has a pyrogallol structure, increased PGI(2) production. These observations indicate that catechins increase the prostacyclin production and that the pyrogallol structure is significant to this function.     

Epigallocatechin gallate and gallocatechin gallate in green tea catechins inhibit extracellular release of Vero toxin from enterohemorrhagic Escherichia coli O157:H7

We studied the effects of six catechin derivatives (catechin, epigallocatechin, epicatechin, epicatechin gallate, epigallocatechin gallate (EGCg) and gallocatechin gallate (GCg)) in green tea on the production and extracellular release of Vero toxins (VTs) from enterohemorrhagic Escherichia coli (EHEC) cultured at 37 degrees C for 24 h. EGCg and GCg in the culture medium markedly inhibited extracellular VTs release from EHEC cells into the culture supernatant fluid at concentrations of 0.05 mg/ml or higher, as estimated by both the reversed passive latex agglutination assay and cytotoxic assay using Vero cells. Production and extracellular release of maltose binding protein, a periplasmic protein, into the culture supernatant were also inhibited by EGCg and GCg, indicating that their inhibitory effect on release from periplasm into the outer milieu is not specific to VTs, but general to the proteins accumulated in EHEC periplasm.     

Epigallocatechin gallate-induced apoptosis does not affect adipocyte conversion of preadipocytes

In the present study, we examined the effect of epigallocatechin gallate (EGCG) on the growth and differentiation of human preadipocyte cells, AML-I. EGCG exhibited cytotoxic activity on AML-I cells, accompanied by the appearance of characteristics of apoptosis by Annexin V-FITC staining method. Among apoptosis-related proteins examined, loss of NF-kappaB and p-Akt, and accumulation of Bad were displayed in EGCG-treated cells by Western blot analysis. Among 6 structure-related catechins including catechin (C), epicatechin (EC), catechin gallate (CG), epigallocatechin (EGC), epicatechin gallate (ECG) and EGCG, the catechins containing galloyl moiety exhibited apoptotic capacity. Interestingly, exposure of AML-I to EGCG increased the amounts of cytoplasmic lipid droplets as well as the expression of fatty acid synthase and peroxisome proliferator activated receptor-gamma proteins. Our results suggest that EGCG induces growth arrest and apoptosis, but does not affect adipocyte conversion of preadipocytes.     

Structure-activity relationship of the tocopherol-regeneration reaction by catechins

The reaction rates (k(r)) of 5,7-diisopropyl-tocopheroxyl radical (Toc) with catechins (epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), epigallocatechin gallate (EGCG)) and related compounds (methyl gallate (MG), 4-methylcatechol (MC), and 5-methoxyresorcinol (MR)) have been measured by stopped-flow spectrophotometer. The k(r) values increased in the order of MR < < MG < EC < MC approximately ECG < EGC < EGCG in ethanol and 2-propanol/H(2)O (5/1, v/v) solutions, indicating that the reactivity of the OH groups in catechins increased in the order of resorcinol A-ring < < gallate G-ring < catechol B-ring < pyrogallol B-ring. The catechins which have lower oxidation potentials show higher reactivities. The rate constants for catechins in micellar solution showed notable pH dependence with one or two peaks around pH 9-11, because of the dissociation of various phenolic hydroxyl protons in catechins. The structure-activity relationship in the free-radical-scavenging reaction by catechins has been clarified by the detailed analyses of the pH dependence of k(r) values. The reaction rates increased remarkably with increasing the anionic character of catechins, that is, the electron-donating capacity of catechins. The mono anion form at catechol B-and resorcinol A-rings and dianion form at pyrogallol B-and gallate G-rings show the highest activity for free-radical-scavenging. It was found that catechins (EC, ECG, EGC, and EGCG) have activity similar to or higher than that of vitamin C in vitamin E regeneration at pH 7-12 in micellar solution.     

Differential effect of green tea catechins on three endothelial cell clones isolated from rat adipose tissue and on human umbilical vein endothelial cells

By single colony isolation from the cells in stromal vascular fraction (SVF) dispersed from rat adipose tissues, we isolated three independent clones with different proliferation potential. All clones showed cobblestone-like morphology at the confluence and incorporated fluorescent Dil acetylated low density lipoprotein. When plated on Matrigel, they formed a capillary network-like structure. These rat adipose tissue endothelial cell (RATEC) clones showed higher expression of wnt2, wnt4, wnt5a, wnt5b, fzd1 and fzd5 whereas lower expression of cell cycle controlling genes such as CIP1, KIP1, KIP2, CDKN2A, CDKN2B, CDKN2C and CDKN2D compared to human umbilical vein endothelial cell (HUVEC). As reported for HUVEC, the growth of RATEC was inhibited by green tea catechins such as epigallocatechin, epicatechin gallate, epicatechin and epigallocatechin gallate but with higher sensitivity than HUVEC. The sensitivity of RATEC to catechins was higher for the cultures with low plating density and for the clone with higher proliferation potential.     

Flavanols in somatic cell division and male meiosis of tea (Camellia sinensis) anthers

Young anthers excised from closed tea flower buds ( Camellia sinensis L.) were stained as fresh tissues with p-dimethylaminocinnamaldehyde reagent to localize flavanols associated with nuclei and chromosomes, apart from those flavanols stored in vacuoles. This staining reagent yields a blue colour for flavanols. In the nonsporogenic somatic cells of developing anthers, flavanols were found to be attached to chromosomes at all mitotic stages. Male meiosis started at a bud size of about 3.5 mm in diameter in pollen mother cells which displayed generally more or less pronounced blue nuclei and cytoplasm. The meiotic divisions from prophase I to telophase II were characterized by blue stained nuclei and chromosomes, but within the cytoplasm there was, if any, a random and very poor reaction for flavanols. Metaphase and telophase of meiotic divisions showed maximally condensed chromosomes staining dark blue. Early in telophase II, the cytoplasm was again stained blue; this faded at late tetrad stage. Flavanols of young mitotic and older non-mitotic anthers were determined using high pressure liquid chromatography--chemical reaction detection (HPLC-CRD). Catechin, epicatechin, B2, and epigallocatechin were minor compounds, whereas epicatechin gallate and epigallocatechin gallate were found in higher amounts. The major flavanol compound of the anthers, epicatechin gallate, exhibited a significant affinity to histone sulphate, as shown by UV-VIS spectroscopic titration.     

Catechins delay lipid oxidation and alpha-tocopherol and beta-carotene depletion following ascorbate depletion in human plasma

Blood plasma was incubated with 50 mM AAPH [2, 2'-azobis-(2-amidinopropane) hydrochloride] in the absence or presence of catechins (5-100 microM). Lipid oxidation was evaluated by measuring the formation of 2-thiobarbituric acid reactive substances (TBARS). The concentration of alpha-tocopherol (AT), beta-carotene (BC), ascorbic acid (AA), and catechins was determined by reverse phase high performance liquid chromatography (HPLC) with electrochemical detection. All the assayed catechins inhibited plasma TBARS formation. Based on the calculated IC50, the order of effectiveness was: epicatechin gallate (ECG) > epigallocatechin gallate (EGCG) > epigallocatechin (EGC) > epicatechin (EC) > catechin (C). Catechins protected plasma AT and BC from AAPH-mediated oxidation. The order of effectiveness for AT protection was ECG > EGCG > EC = C > EGC; and for BC protection, the order was EGCG > ECG > EGC > > EC > C. The addition of catechins modified the kinetics of TBARS formation and AT depletion, but the rate of AA depletion was not affected. Catechin oxidation did not start until the complete depletion of AA, and it preceded AT depletion. These results indicate that catechins are effective antioxidants in human blood plasma, delaying the lipid oxidation and depletion of endogenous lipid-soluble antioxidants (AT and BC).     

Kinetic study of the quenching reaction of singlet oxygen by tea catechins in ethanol solution

A kinetic study of the quenching reaction of singlet oxygen ((1)O(2)) with catechins (catechin (CA), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), epigallocatechin gallate (EGCG)) and related compounds (5-methoxyresorcinol (MR), 4-methylcatechol (MC), and n-propyl gallate (PG)) was performed in ethanol at 35 degrees C. MR, MC, and PG are considered to be a model of resorcinol (A)-, catechol (B)-, and gallate (G)-rings in catechins, respectively. The overall rate constants, k(Q) (= k(q) + k(r), physical quenching + chemical reaction), for the reaction of catechins with (1)O(2) increased in the order of PG < MR < MC < CA < EC < EGC < ECG < EGCG. In a comparison of the rate constants, the relationship between quenching rates and chemical structures is discussed. The catechins which have lower peak oxidation potentials, E(P), show higher reactivities. It was observed that the chemical reaction (k(r)) is almost negligible in the quenching reaction of (1)O(2) by catechins. The k(Q) values of EGCG (1.47 x 10(8) M(-1) s(-1)) and ECG (7.81 x 10(7)) were found to be larger than those of lipids (1.3 x 10(5)-1.9 x 10(5) M(-1) s(-1)), amino acids (<3.7 x 10(7)), and DNA (5.1 x 10(5)). Further, these values are similar to those (1.15 x 10(8)-2.06 x 10(8) M(-1) s(-1)) of alpha- and gamma-tocopherol, ubiquinol-10, and gamma-tocopherol hydroquinone (plastoquinol model). The result suggests that catechins may contribute to the protection of oxidative damage in biological systems, by quenching (1)O(2).