Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Tea”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources

Comparison of cytotoxicity and radical scavenging activity between tea extracts and Chinese medicines.

Three hot water extracts of black tea, green tea and powdered green tea and five Chinese medicines (Shosaiko-tou, Orengedoku-tou, Goshuyu-tou, Choto-san, Keishininjinn-tou) were investigated for their ability to modify nitric oxide (NO) production by lipopolysaccharide (LPS)-stimulated mouse macrophage-like Raw 264.7 cells, and for their cytotoxicity, radical intensity and scavenging activity. All eight materials significantly reduced the extracellular concentration of NO in the LPS-stimulated Raw 264.7 cells. ESR spectroscopy shows that tea extracts, which had higher cytotoxicity, generated higher amounts of radicals, and more efficiently scavenged O2- (generated by hypoxanthine-xanthine oxidase reaction), hydroxyl radical (generated by Fenton reaction) and NO (generated by 1-hydroxyl-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene) than Chinese medicines. Close association between the radical intensity and radical scavenging activity suggests their bimodal (anti-oxidant and pro-oxidant) action. Pretreatment of mice with tea extracts significantly reduced the lethality of Escherichia coli-infection. All tea extracts showed no apparent anti-HIV activity. The present study demonstrates, for the first time, several attractive features of tea extracts in comparison with Chinese medicines, suggesting the possible application of the tea extracts for radical-mediated diseases.

Animals↗

Anticariogenic effects of green tea.

The effects of green tea extract on caries inhibition of hamsters and on acid resistance of human tooth enamel have been investigated. Both in vivo and in vitro experiments showed that original extract of green tea had the significant effects on these points. The dialyzed tea solution in which the fluoride was removed almost completely, also showed the remarkable effects both in vivo and in vitro experiment as is similar to the original tea extract. The results obtained from this study suggested that fluoride in green tea may play a role to increase the cariostatic action in cooperation with other components in tea. However, the action of fluoride does not seem to be so important, because its concentration is very low. The effect of green tea on caries inhibition as well as on the increment of acid resistance appears to be more correlative with the non-dialysable substances in tea.

Animals↗

Inhibition of tobacco-specific nitrosamine-induced lung tumorigenesis in A/J mice by green tea and its major polyphenol as antioxidants.

In this study we examined the effects of green tea and its major components, (-)-epigallocatechin gallate (EGCG) and caffeine, on the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice. We also studied the effects of green tea and EGCG on O6-methylguanine and 8-hydroxydeoxyguanosine (8-OH-dGuo) formation in lung tissues caused by NNK treatment. Mice were given 2% tea, 560 ppm EGCG, or 1120 ppm caffeine in drinking water for 13 weeks. During this time, NNK (11.65 mg/kg body weight) was administered by gavage three times weekly for 10 weeks from weeks 3 to 12. The bioassay was terminated 6 weeks after the last NNK treatment. Mice treated with NNK developed 22.5 lung adenomas per mouse, whereas NNK-treated mice that drank green tea or EGCG as drinking water developed only 12.2 (P less than 0.01) and 16.1 (P less than 0.05) tumors per mouse, respectively. Mice that drank green tea or caffeine solution showed lower body weight gains, although little difference in water and diet consumption was noted in these groups. While green tea and EGCG exerted little effect on the formation of O6-methylguanine, a critical DNA lesion in NNK lung tumorigenesis, both treatments suppressed the increase of 8-OH-dGuo levels in mouse lung DNA. The inhibition of 8-OH-dGuo formation in lung DNA by green tea and EGCG is consistent with their ability to inhibit lung tumorigenesis by NNK. Because 8-OH-dGuo is a DNA lesion caused by oxidative damage, these results suggest that the mechanism of inhibition by green tea and EGCG in NNK-induced lung tumorigenesis is due at least partly to their antioxidant properties.

8-Hydroxy-2'-Deoxyguanosine↗

[Chemical and sensory characterization of tea (Thea sinensis) consumed in Chile].

By means of descriptive analysis four varieties of tea (Thea sinensis) were assesed: Argentinean OP (orange pekoe) tea (black), Brazilian OP tea (black), Ceylan OP tea (black) and Darjeeling OP tea (green). The appearance of dry tea leaves were qualitatively characterized comparing with dry leaves standard. The attributes: colour, form, regularity of the leaves, fibre and stem cutting were evaluated The differences obtained were related to the differences produced by the effect of the fermentation process. Flavour and aroma descriptors of the tea liqueur were generated by a trained panel. Colour and astringency were evaluated in comparison with qualified standards using non structured linear scales. In order to relate the sensory analysis and the chemical composition for the different varieties of tea, following determinations were made: chemical moisture, dry material, aqueous extract, tannin and caffeine. Through multifactor regression analysis the equations in relation to the following chemical parameters were determined. Dry material, aqueous extract and tannins for colour and moisture, dry material and aqueous extract for astringency, respectively. Statistical analysis through ANOVA (3 variation sources: samples, judges and replications) showed for samples four significant different groups for astringency and three different groups for colour. No significant differences between judges or repetitions were found. By multifactor regression analysis of both, colour and astringency, on their dependence of chemist results were calculated in order to asses the corresponding equations.

Analysis of Variance↗

Drinking tea is associated with lower plasma total homocysteine in older women.

Dietary polyphenols are suggested to elevate plasma total homocysteine concentration (tHcy). Although tea is rich in polyphenols, it has been associated with lower tHcy, which may be due to its folate content. Our aims were to investigate relationships of tea intake and 4-O-methylgallic acid (4OMGA)--a biomarker of exposure to tea-derived polyphenols--with tHcy in older women. In a cross-sectional study of 232 women over 70 years of age, we measured tHcy, tea intake, 24 h urinary excretion of 4OMGA, and red cell folate. Tea intake and 4OMGA excretion were inversely related to tHcy. Tea intake (>2 cups) and 4OMGA excretion above the median were associated with lower tHcy by approximately 1 mmol/L (P <0.01). Red cell folate was not associated with tea intake or 4OMGA excretion. The observed lower tHcy in women with higher tea intake is consistent in direction and magnitude with previous epidemiological studies, but any mechanisms remain unclear.

Aged↗

[PH values and fluoride levels in some tea brands].

The purpose of the study was to determine the pH and fluoride levels in selected commercial tea brands sold in supermarkets and to evaluate the importance of tea as a dietary source of fluorine. Thirty six different brands and types of tea in bags were evaluated. In order to prepare the tea, one bag of tea (1.5-2 g) was covered with 200 mL of boiling deionized water for 3 minutes. The pH was measured with a pH-meter and fluoride concentration was determined with an ion-selective electrode (Orion 9609). pH values of the tea infusions ranged from 3.85 to 6.45 (mean 5.24) and fluorides from 0.12 ppm to 8.33 ppm (mean 1.32 ppm). Thus, the individual intake of fluorine is estimated at 0.66 mg per 500 mL of tea. The results confirm that regular consumption of tea is an important dietary source of fluorine.

Dietary Supplements↗

[Determination and analysis of trace element manganese and amino acids content in aloe tea].

The content of trace element manganese in aloe tea was determined by atomic absorption spectrophotometry. The contents of 17 kinds of amino acids in aloe tea were determined with amino acids instrumentation. The results showed that there are comparatively rich manganese and amino acids in aloe tea. The content of manganese in red tea is more than in green tea, and the dissolving ratio is more than 50% in boiled water, and first dissolving ratio is more than second dissolving ratio, which is more than third dissolving ratio. There are 7 kinds of amino acids essential to human body, among which are comparatively high aspartic acid, glutamic acid and leucine in aloe tea. It's outstanding characteristic is comparatively high content of manganese in aloe health tea. It has provided useful data for probing into the relationship between trace elements and amino acids in aloe health tea and health care function.

Aloe↗

Allergic conjunctivitis to chamomile tea.

Eye washing with chamomile tea is a folk remedy used by the general public to treat conjunctivitis and other ocular reactions. Chamomile is also found in many cosmetic products. Some cases of contact dermatitis (but not reactions of type I) were reported following its topical applications. We present seven hay fever patients that suffered from conjunctivitis; two of them also had lid angioedema after eye washing with chamomile tea. All seven patients had positive skin prick tests to the chamomile tea extract, Matricaria chamomilla pollen and Artemisia vulgaris pollen extracts. Positive conjunctival provocations were also observed in all the patients with the chamomile tea extract. In contrast, no symptoms were observed after oral challenges with this infusion. IgE activity against chamomile tea and Matricaria and Artemisia extracts (composite pollens) was detected by ELISA in the seven patients' sera. A cross reactivity among the above extracts was observed by an ELISA inhibition study. In all cases, the IgE activity to chamomile tea could fully be absorbed by Matricaria pollen extract. Skin prick tests and conjunctival provocation tests also performed in 100 hay fever controls revealed a positive immediate skin response to Artemisia in 15 patients, eight of them also to Matricaria pollen and five of them to Chamomile tea as well. Only two of the last patients had a positive conjunctival response. The results were negative in the rest of the controls. We conclude that the chamomile tea eye washing can induce allergic conjunctivitis. Matricaria chamomilla pollens contained in these infusions are the allergens responsible for these reactions.

Administration, Oral↗

Prophylactic effect of tea on pathogenic microorganism infections to humans and animals. (II). Protozoacidal effect on Toxoplasma gondii in vitro and mice.

The trophozoites of Toxoplasma gondii strain (RH) obtained from the peritoneal exudate of infected mice were treated with tea in various concentrations of 0.5, 1, 3 and 5% for 0.5, 1 and 3 hours, respectively. After treatment, they were intraperitoneally inoculated into the mice to observe the protozoacidal effect of tea. The results obtained are as follows: 1) Oolong tea and green tea had stronger protozoacidal effect than black tea. 2) The lowest and effective concentration of tea tested to kill Toxoplasma was 0.5%. 3) A half hour was not enough for tea in any concentration tested to kill the parasites completely. 4) Phosphate buffer solution and normal saline were unable to destroy the protozoa, but distilled water could destroy them like tea.

Animals↗

Modulation of cancer chemotherapy by green tea.

Biochemical modulation has played an important role in the development of cancer chemotherapy. We have directed our attention to the intake of common beverages and investigated the effects of green tea and tea components on the antitumor activity of doxorubicin. We carried out the combined treatment of toxorubicin and green tea on Ehrlich ascites carcinoma tumor-bearing mice. The oral administration of green tea enhanced 2.5-fold the inhibitory effects of doxorubicin on tumor growth. The Doxorubicin concentration in the tumor was increased by the combination of green tea with doxorubicin. In contrast, the increase in doxorubicin concentration was not observed in normal tissues after green tea combination. Furthermore, the enhancement of antitumor activity of doxorubicin induced by green tea was observed in M5076 ovarian sarcoma, which has low sensitivity to doxorubicin. These results suggest that drinking green tea can encourage cancer chemotherapy and may improve the quality of life of clinical patients.

Animals↗

Human salivary tea catechin levels and catechin esterase activities: implication in human cancer prevention studies.

Because of the possible application of tea in the prevention of oral and esophageal cancers, the salivary levels of tea catechins were determined in six human volunteers after drinking tea. Saliva samples were collected after thoroughly rinsing the mouth with water. After drinking green tea preparations equivalent to two to three cups of tea, peak saliva levels of (-)-epigallocatechin (EGC; 11.7-43.9 microg/ml), EGC-3-gallate (EGCG; 4.8-22 microg/ml), and (-)-epicatechin (EC; 1.8-7.5 microg/ml) were observed after a few minutes. These levels were 2 orders of magnitude higher than those in the plasma. The elimination half-life (t(1/2)) of the salivary catechins was 10-20 min, much shorter than that of the plasma. Holding a tea solution in the mouth for a few minutes without swallowing produced even higher salivary catechin levels, but taking tea solids in capsules resulted in no detectable salivary catechin level. Holding an EGCG solution in the mouth resulted in EGCG and EGC in the saliva and, subsequently, EGC in the urine. The results suggest that EGCG was converted to EGC in the oral cavity, and both catechins were absorbed through the oral mucosa. A catechin esterase activity that converts EGCG to EGC was found in the saliva. The enzyme was likely of human origin, but the activity was not inhibited by common human esterase inhibitor. The present results suggest that slowly drinking tea is a very effective way of delivering rather high concentrations of catechins to the oral cavity and then the esophagus.

Absorption↗

Separation of catechin compounds from different teas.

Catechin compounds from Korean and Chinese green tea, and pu-erh, Indian black, Longjing, Tieguanyin, Bamboo, Jasmine, Oolong, Flower, Red teas, as potential anticancer and antioxidant components, were target material in this work. After extracting the green tea with water at 50 degrees C for 4 h, the extract was partitioned with water/chloroform, which was best suited to remove caffeine impurity from the extract. Further, the resulting extract was partitioned with water/ethyl acetate to deeply purify the five catechin compounds epigallocatechin, (+) catechin, epicatechin, epigallocatechin gallate and epicatechin gallate. The extracted samples were analyzed by reversed-phase high performance liquid chromatography. The mobile phase applied was the binary system of A (water/acetic acid, 100/0.1 vol%) and B (acetonitrile/acetic acid 100/0.1 vol%) from 90:10 to 70:30 (A:B vol%) in a linear gradient over 30 min time. The amount of catechin compounds extracted from Chinese green tea was 114.65% higher than from the Korean green tea. Comparing various tea sorts, the green teas contained more than 1.7 times of the five catechin compounds contained in other teas.

Camellia sinensis↗

Contribution of T-type VDCC to TEA-induced long-term synaptic modification in hippocampal CA1 and dentate gyrus.

We have previously reported that exposure to the K+ channel blocker tetraethylammonium (TEA), 25 mM, induces long-term potentiation (LTP) in CA1, but not in the dentate gyrus (DG), of the rat hippocampal slice. During TEA application, stimulation of excitatory afferents results in a strong depolarizing potential after the fast excitatory postsynaptic potential (EPSP) in CA1, but not in DG. We hypothesized that the differential effect of TEA on long-term synaptic modification in CA1 and DG results from different levels of TEA-elicited depolarization in the two cell types. Additional pharmacological studies showed that blockade of T-type voltage-dependent calcium channels (VDCCs) decreased both the magnitude of LTP and the late, depolarizing potential in CA1. Blockade of L-type VDCCs had no such effect. Using computer models of morphologically reconstructed CA1 pyramidal cells and DG granule cells, we tested our hypothesis by simulating the relative intracellular Ca2+ accumulation and membrane potential changes mediated by T-type and L-type VDCCs. Simulation results using pyramidal cell models showed that, with decreased maximum conductance of TEA-sensitive potassium channels, synaptic inputs elicited strong depolarizing potentials similar to those observed with intracellular recording. During this depolarization, VDCCs were opened and resulted in a large intracellular Ca2+ accumulation that presumably caused LTP. When T-type VDCCs were blocked, the magnitudes of both the Ca2+ accumulation and the late depolarizing potential were decreased substantially. Simulated blockade of L-type VDCCs had only a minor effect. Together, our modeling and experimental studies indicate that T-type VDCCs, rather than L-type VDCCs, are primarily responsible for facilitating the depolarizing potential caused by TEA and for the consequent Ca2+ influx. Thus, our findings strongly suggest that the induction of TEA-LTP in CA1 depends primarily on T-type, rather than L-type, VDCCs. Simulation results using modeled granule cells suggests that the failure of TEA to induce LTP in DG is partly due to a low density of T-type VDCCs in granule cell membranes.

Animals↗

Evidence for coupling between Na+ pump activity and TEA-sensitive K+ currents in Xenopus laevis oocytes.

Using the two-microelectrode voltage clamp technique in Xenopus laevis oocytes, we estimated Na(+)-K(+)-ATPase activity from the dihydroouabain-sensitive current (IDHO) in the presence of increasing concentrations of tetraethylammonium (TEA+; 0, 5, 10, 20, 40 mM), a well-known blocker of K+ channels. The effects of TEA+ on the total oocyte currents could be separated into two distinct parts: generation of a nonsaturating inward current increasing with negative membrane potentials (VM) and a saturable inhibitory component affecting an outward current easily detectable at positive VM. The nonsaturating component appears to be a barium-sensitive electrodiffusion of TEA+ which can be described by the Goldman-Hodgkin-Katz equation, while the saturating component is consistent with the expected blocking effect of TEA+ on K+ channels. Interestingly, this latter component disappears when the Na(+)-K(+)-ATPase is inhibited by 10 microM DHO. Conversely, TEA+ inhibits a component of IDHO with a KD of 25 +/- 4 mM at +50 mV. As the TEA(+)-sensitive current present in IDHO reversed at -75 mV, we hypothesized that it could come from an inhibition of K+ channels whose activity varies in parallel with the Na(+)-K(+)-ATPase activity. Supporting this hypothesis, the inward portion of this TEA(+)-sensitive current can be completely abolished by the addition of 1 mM Ba2+ to the bath. This study suggests that, in X. laevis oocytes, a close link exists between the Na-K-ATPase activity and TEA(+)-sensitive K+ currents and indicates that, in the absence of effective K+ channel inhibitors, IDHO does not exclusively represent the Na(+)-K(+)-ATPase-generated current.

Animals↗

[Impact of green tea on oxidative stress induced by ammonium metavanadate exposure in male rats].

Transitional metals, as vanadium, are known to exert noxious effects by generating oxidative stress. Addition of antioxidants in the diet could decrease the cytotoxic effect related to the oxidative stress. The present study, carried out in Wistar rats, is a contribution to the evaluation of protective effects of green tea Camellia sinensis, which is known to be rich in antioxidant compounds (polyphenols...). Rats were divided into four groups: (C) was control, (V) was given ammonium metavanadate (AMV), (TH) was given herbal tea as drink (66 g/l) and TH + V was given tea and metavanadate. Group (TH) was given herbal tea one month before vanadium treatment. Metavanadate was daily i.p. injected (5 mg NH4VO3/kg body weight) for 10 days. (C) and (TH) groups received i.p. injections of 0.9% NaCl during the same period. Changes in lipid peroxidation levels (TBARS) in kidney, liver and testes, serum concentrations of vitamins E and A and superoxidismutase (SOD) and catalase (CAT) activities in blood cells were determined. One month pre-treatment with green tea, followed by 10 days of treatment (TH) did not change TBARS in liver and testes as compared to controls, but induced a clear decrease of TBARS in kidneys. Intraperitoneal administration of AMV to rats (V) induced a time-dependant increase of TBARS in kidney, liver and testes that was lowered in rats (V + TH) drinking tea. Vitamin E concentrations were found to be drastically decreased from day 1 to 10 in rats (V). Vitamin A concentration was decreased at day 10 only. Drinking tea lowered AMV inhibitory effects in rats (V + TH), and conversely an increase of vitamins A and E concentrations were found at day 10. SOD and catalase activities were found increased in the blood cells from day 1 to day 5 and conversely decreased at day 10. In contrast, associated to green tea, AMV did not affect SOD and catalase activities compared to controls.

Animals↗

Protective effect of green tea extract on ischemia/reperfusion-induced brain injury in Mongolian gerbils.

Free radical-induced oxidative damages of macromolecules and cell death are important factors in the pathogenesis of ischemia/reperfusion brain injury. In the present study, an investigation as to whether green tea extract reduces ischemia/reperfusion-induced brain injury in Mongolian gerbils was conducted. The effect of green tea on the ischemia/reperfusion-induced production of hydrogen peroxide, lipid peroxidation and oxidative DNA damage (formation of 8-hydroxydeoxyguanosine), and cell death in addition to locomotor activity was studied. Two doses (0.5 or 2%) of green tea extract were added into the drinking water and to be accessed by animals ad libitum for 3 weeks prior to the induction of ischemia. A global ischemia was induced by the bilateral occlusion of the common carotid arteries for 5 min. Reperfusion was achieved by releasing the occlusion and restoring blood circulation for 48 h. The infarction volumes were 112+/-31 mm(3) and 76+/-11 mm(3) in the 0.5 and 2% green tea pretreated animals compared to 189+/-12 mm(3) in the ischemia/reperfusion animals. Green tea extract also reduced the levels of ischemia/reperfusion-induced hydrogen peroxide (from 1470+/-170 to 1034+/-46 and 555+/-30 nmole/mg protein), lipid peroxidation products (from 1410+/-210 to 930+/-40 and 330+/-20 nmole/mg protein) and 8-oxodG (from 3.9+/-0.1 to 2.8+/-0.3 and1.9+/-0.3 ng/microg DNA, x10(-2)) by pretreatment of 0.5 or 2% green tea for 3 weeks, respectively. Moreover, green tea also reduced the number of ischemia/reperfusion-induced apoptotic cells (from 59+/-12 to 37+/-8, 15+/-11 apoptotic cells/high power field in the striatum region) and locomotor activity (from 15140+/-2940 to 3900+/-600 and 4100+/-1200). This study therefore suggests that green tea may be a useful agent for the prevention of cerebral ischemia damage.

8-Hydroxy-2'-Deoxyguanosine↗

Identification by HPLC-DAD and HPLC-MS analyses and quantification of constituents of fennel teas and decoctions.

Qualitative and quantitative differences among the constituents in various fennel (Foeniculum vulgare Mill., family Apiaceae) teas prepared by classical infusion, microwave decoction, and dissolution are reported. Different commercial starting materials, such as fruit (unbroken and crushed), four herbal teas, and two instant herbal teas were evaluated. Chlorogenic acid (1), quercetin-3-O-beta-D-glucuronide (2), p-anisaldehyde (3), and trans-anethole (4) were identified by HPLC-DAD and HPLC-MS as constituents of fennel teas. No coumarins, which are characteristic constituents of plants of Apiaceae family, were found. Trans-anethole (4), the main constituent of the essential oil, was present in all teas. In addition p-anisaldehyde (3), a degradation product of trans-anethole, was also identified in all teas with the exception of two samples. Chlorogenic acid (1) and quercetin-3-O-beta-D-glucuronide (2) were also present in all teas. In addition, minor unidentified flavonol constituents were found in two teas. Quality, activity, and safety of the content of the investigated preparations are also discussed.

Beverages↗

Seasonal variations of phenolic compounds in Australia-grown tea (Camellia sinensis).

Seasonal variations of phenolic compounds in fresh tea shoots grown in Australia were studied using an HPLC method. Three principal tea flavanols [epigallocatechin gallate (EGCG), epicatechin gallate (ECG), and epigallocatechin (EGC)] and four grouped phenolics [total catechins (Cs), total catechin gallates (CGs), total flavanols (Fla), and total polyphenols (PPs)] in fresh tea shoots were analyzed and compared during the commercial harvest seasons from April 2000 to May 2001. The levels of EGCG, ECG, and CGs in the fresh tea shoots were higher in the warm months of April 2000 (120.52, 34.50, and 163.75 mg/g, respectively) and May 2000 (128.63, 44.26, and 183.83 mg/g, respectively) and lower during the cool months of July 2000 (91.39, 35.16, and 132.30 mg/g, respectively), August 2000 (91.31, 31.56, and 128.64 mg/g, respectively), and September 2000 (96.12, 33.51, and 136.90 mg/g, respectively). Thereafter, the levels increased throughout the warmer months from October to December 2000 and remained high until May 2001. In the warmer months, the levels of EGCG, ECG, and CGs were in most cases significantly higher (P < 0.05) than those in the samples harvested in the cooler months. In contrast, the levels of EGC and Cs were high and consistent in the cooler months and low in the warmer months. The seasonal variations of the individual and grouped catechins were significant (P < 0.05) between the cooler and warmer months. This study revealed that EGCG and ECG could be used as quality descriptors for monitoring the seasonal variations of phenolics in Australia-grown tea leaves, and the ratio (EGCG + ECG)/EGC has been suggested as a quality index for measuring the differences in flavanol levels in fresh tea shoots across the growing seasons. Mechanisms that induce seasonal variations in tea shoots may include one or all three of the following environmental conditions: day length, sunlight, and/or temperature, which vary markedly across seasons. Therefore, further studies under controlled conditions such as in a greenhouse may be required to direct correlate flavonoid profiles of green tea leaves with their yields and also to with conditions such as rainfall and humidity.

Australia↗