Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
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| biosynthesis and catabolism of caffeine in low-caffeine-containing species of coffea. | leaves of coffea salvatrix, coffea eugenioides, and c. bengalensis contain approximately 3-7-fold lower levels of caffeine than those of coffea arabica. there was more extensive biosynthesis of caffeine from [8-(14)c]adenine in young leaves of c. arabica than in c. salvatrix, c. eugenioides, and c. bengalensis. degradation of [8-(14)c]caffeine, which is negligible in leaves of c. arabica, was also very slow in c.salvatrix and c. bengalensis. in contrast, [8-(14)c]caffeine was catabolized rapidly ... | 1999 | 10552667 |
| novel antiallergic catechin derivatives isolated from oolong tea. | two catechin derivatives (c-1 and c-2) with potent antiallergic activity were isolated from taiwanese oolong tea by hplc techniques. from nmr and fab-ms analyses, the structures of c-1 and c-2 were elucidated as (-)-epigallocatechin 3-o-(3-o-methyl)gallate and (-)-epigallocatechin 3-o-(4-o-methyl)gallate, respectively. the oolong tea leaves contained 0.34% (dry weight) c-1 and 0.20% c-2. traces of c-2 were detected in only 1 of 15 varieties of green tea tested. c-1 was detected in 13 of 15 green ... | 1999 | 10552469 |
| (z)-3-hexenyl and trans-linalool 3,7-oxide beta-primeverosides isolated as aroma precursors from leaves of a green tea cultivar. | 6-o-beta-d-xylopyranosyl-beta-d-glucopyranosides (beta-primeverosides) of (z)-3-hexenol and trans-linalool 3,7-oxide were newly isolated from fresh leaves of a tea cultivar (camellia sinensis var. sinensis cv. yabukita). in addition, the already identified beta-primeverosides of benzyl alcohol, methyl salicylate, and trans-linalool 3,6-oxide from an oolong tea cultivar were isolated from the yabukita cultivar. it was confirmed that all aglycones of the linalool oxide glycosides isolated here wer ... | 1999 | 10540751 |
| inhibition of tpa-induced protein kinase c and transcription activator protein-1 binding activities by theaflavin-3,3'-digallate from black tea in nih3t3 cells. | tea is one of the most popular beverages in the world. several reports have shown that both green tea and black tea were able to inhibit tumor cell proliferation in animal models. in this study, we investigated the inhibitory effects of black tea polyphenols including theaflavin (tf-1), the mixture (tf-2) of theaflavin-3-gallate (tf-2a), and theaflavin-3'-gallate (tf-2b), theaflavin-3,3'-digallate (tf-3), thearubigin (tr), and a major green tea polyphenol (-)-epigallocatechin-3-gallate (egcg) on ... | 1999 | 10563991 |
| total antioxidant capacity of teas by the ferric reducing/antioxidant power assay. | this study aimed to compare in vitro antioxidant power of different types of tea (camellia sinensis). the ferric reducing/antioxidant power (frap) assay was used to measure the total antioxidant power of freshly prepared infusions of 25 types of teas. results showed that different teas had widely different in vitro antioxidant power and that the antioxidant capacity was strongly correlated (r = 0. 956) with the total phenolics content of the tea. expressed as micromol of antioxidant power/g of d ... | 1999 | 10563944 |
| green tea (camellia sinensis) extract and its possible role in the prevention of cancer. | the american cancer society estimates that in the 1980s more than 4. 5 million americans died of cancer. in addition, there were nearly nine million new cases and about 12 million people were under medical care for cancer. with cancer being the second most common cause of death in the united states population, the possibility that readily-available natural substances may be beneficial in the prevention of cancer warrants closer examination. a growing body of research has demonstrated green tea p ... | 1999 | 10559550 |
| identification of endogenous gibberellins in the leaves and xylem sap of tea plants. | endogenous gibberellins (gas) in the young leaves and xylem sap of tea plants (camellia sinensis l.) were analyzed by gc-ms. the following gas were identified by comparing their mass spectra and kris with those of authentic specimens: ga9 and ga20 in the leaves; ga9, ga12, ga15, ga20, ga44, ga51 and ga53 in the xylem sap. | 1999 | 27392877 |
| statistical analysis of salivary ph changes after the intake of black tea and yerba maté supplemented with sweeteners. | many studies have demonstrated the effect of various beverages on hard tissues of the mouth. sugar consumption has also been avoided because it is associated with caries activity, and artificial sweetener research has been promoted. in this paper, data about the buffer capacity of black tea and yerba mate supplemented with sugar or one of two artificial sweeteners (barny diet and nutrasweet) were examined. salivary ph variations after the ingestion of both infusions were statistically analysed. ... | 1999 | 10453132 |
| proconvulsive effect of tea (camellia sinensis) in mice. | investigations were carried out to evaluate the effect of acute and chronic administration of both black and green tea on three models of experimentally induced convulsions in mice. tea extract (both black and green) significantly accelerated the onset of convulsion, increased the duration of convulsion and mortality in mice. since both the extracts failed to alter the gaba level in brain, based on the earlier report that both black and green tea might act on ca(2+) channels, it can be suggested ... | 1999 | 10441775 |
| effects on blood pressure of drinking green and black tea. | the flavonoid components of tea have been associated in epidemiological studies with a decreased risk of cardiovascular disease. flavonoids have been shown to have antioxidant and vasodilator effects in vitro; we therefore postulated that drinking green or black tea attenuates the well-characterized acute pressor response to caffeine and lowers blood pressure during regular consumption. | 1999 | 10404946 |
| scavenging of hydrogen peroxide and inhibition of ultraviolet light-induced oxidative dna damage by aqueous extracts from green and black teas. | aqueous extracts of green and black teas have been shown to inhibit a variety of experimentally induced animal tumors, particularly ultraviolet (uv) b light-induced skin carcinogenesis. in the present study, we compared the effects of different extractable fractions of green and black teas on scavenging hydrogen peroxide (h2o2), and uv irradiation-induced formation of 8-hydroxy 2'-deoxyguanosine (8-ohdg) in vitro. green and black teas have been extracted by serial chloroform, ethyl acetate and n ... | 1999 | 10401606 |
| genetic and dietary predictors of cyp2e1 activity: a phenotyping study in hawaii japanese using chlorzoxazone. | cytochrome p4502e1 (cyp2e1) is considered to play an important role in the metabolic activation of procarcinogens such as n-nitrosoamines and low molecular weight organic compounds. an rsai polymorphism is present in the 5'-flanking region of the cyp2e1 gene, which could possibly affect its transcription. however, the relationship between genotype and the phenotypic catalytic activity of the enzyme has not been defined. also, the effects in humans of specific dietary factors, other than ethanol, ... | 1999 | 10385138 |
| a review of plants used in the treatment of liver disease: part two. | botanical medicines have been used traditionally by herbalists and indigenous healers worldwide for the prevention and treatment of liver disease. clinical research in this century has confirmed the efficacy of several plants in the treatment of liver disease, while basic scientific research has uncovered the mechanisms by which some plants provide their therapeutic effects. this article is part two in a review of botanicals used in the treatment of liver disease. curcuma longa (turmeric), camel ... | 1999 | 10383482 |
| effects of oral administration of tea, decaffeinated tea, and caffeine on the formation and growth of tumors in high-risk skh-1 mice previously treated with ultraviolet b light. | treatment of skh-1 mice with ultraviolet b light (uv-b, 30 mj/cm2) twice a week for 22-23 weeks resulted in tumor-free animals with a high risk of developing malignant and nonmalignant tumors during the next several months in the absence of further uv-b treatment (high-risk mice). in three separate experiments, oral administration of green tea or black tea (4-6 mg tea solids/ml) as the sole source of drinking fluid for 18-23 weeks to these high-risk mice inhibited the formation and decreased the ... | 1999 | 10368809 |
| purification and characterization of caffeine synthase from tea leaves. | caffeine synthase (cs), the s-adenosylmethionine-dependent n-methyltransferase involved in the last two steps of caffeine biosynthesis, was extracted from young tea (camellia sinensis) leaves; the cs was purified 520-fold to apparent homogeneity and a final specific activity of 5.7 nkat mg-1 protein by ammonium sulfate fractionation and hydroxyapatite, anion-exchange, adenosine-agarose, and gel-filtration chromatography. the native enzyme was monomeric with an apparent molecular mass of 61 kd as ... | 1999 | 10364410 |
| tea and health: the underlying mechanisms. | detailed multidisciplinary research on the effect of tea and the associated tea polyphenols has led to major advances on the underlying mechanisms. in most studies, green and black tea have similar effects, four of which are reviewed in this paper. 1) tea polyphenols are powerful antioxidants that may play a role in lowering the oxidation of ldl-cholesterol, with a consequent decreased risk of heart disease, and also diminish the formation of oxidized metabolites of dna, with an associated lower ... | 1999 | 10202402 |
| inhibitory effect of green and black tea on tumor growth. | the administration of green tea, black tea, or (-)-epigallocatechin gallate inhibited the growth of established nonmalignant and malignant tumors in tumor-bearing mice. in experiments with black tea, we found that its oral administration inhibited dna synthesis and enhanced apoptosis in both nonmalignant and malignant tumors in tumor-bearing mice. | 1999 | 10202394 |
| preclinical efficacy studies of green and black tea extracts. | 1999 | 10202390 | |
| plasma and lipoprotein levels of tea catechins following repeated tea consumption. | epidemiological studies suggest that antioxidant flavonoids in tea may reduce the risk of cardiovascular disease, possibly via protection of low-density lipoproteins (ldl) against oxidation. however, the extent of absorption of tea flavonoids and their accumulation in ldl during regular consumption of tea is not clear. therefore we investigated plasma and lipoprotein levels of catechins during tea consumption and the impact on ldl oxidizability ex vivo. eighteen healthy adults consumed, in an in ... | 1999 | 10202389 |
| theaflavin-3,3'-digallate from black tea blocks the nitric oxide synthase by down-regulating the activation of nf-kappab in macrophages. | nitric oxide (no) plays an important role in inflammation and also in multiple stages of carcinogenesis. we investigated the effects of various tea polyphenols, including theaflavin, a mixture of theaflavin-3-gallate and theaflavin-3'-gallate, theaflavin-3,3'-digallate, thearubigin, and (-)-epigallocatechin-3-gallate on the induction of no synthase in lipopolysaccharide-activated murine macrophages, raw 264.7 cells. theaflavin-3,3'-digallate was found to be stronger than (-)-epigallocatechin-3-g ... | 1999 | 10079014 |
| antioxidant capacity and polyphenolic components of teas: implications for altering in vivo antioxidant status. | the oxygen radical absorbance capacity (orac) assay was used to determine the total antioxidant capacity of tea. green and black teas (n = 18) had a mean antioxidant capacity of 761.1 +/- 85.3 micromol trolox equivalents (te) per g dry matter. however, their antioxidant capacity varied from 235 micromol to over 1526 micromol trolox equivalents (te)/g dry matter, and total phenolics ranged from 32 to 147 mg/g in different commercial teas. one tea phenolics extract had an antioxidant capacity of 4 ... | 1999 | 10202399 |
| protection by black tea and green tea against uvb and uva + b induced skin cancer in hairless mice. | the effects of green and black tea consumption on the early indices of uvb and uva + b skin damage in hairless mice have been studied in the absence of any chemical tumour initiators or promoters. black tea consumption was associated with a reduction in the number of sunburn cells in the epidermis of mice 24 h after uva + b irradiation, although there was no effect of green tea. other indices of early damage such as necrotic cells or mitotic figures were not affected. neutrophil infiltration as ... | 1998 | 9920445 |
| biokinetic studies in humans with stable isotopes as tracers. part 2: uptake of molybdenum from aqueous solutions and labelled foodstuffs. | molybdenum (mo) has been identified as an essential trace mental for humans. the present study was aimed at the assessment of data on intestinal mo absorption from aqueous solutions and from foodstuffs in humans applying the methodology for intrinsic labelling described in part 1. the intestinal absorption of mo was investigated by means of a double tracer method in 3 healthy volunteers on a total of 15 occasions. when administered as aqueous solution, almost complete uptake of mo was observed u ... | 1998 | 9919682 |
| protection by tea against uv-a + b-induced skin cancers in hairless mice. | consumption of tea, especially green tea, has been shown to reduce the incidence of ultraviolet (uv)-related skin tumors in hairless mice. because milk is added to much of the tea consumed in western cultures, we have studied the effects of including milk in the tea consumed by hairless mice receiving simulated solar radiation. under these conditions, mice consuming tea with 10% whole milk had 30% fewer papillomas, 50% fewer tumors, and 55% smaller lesions than mice consuming water. mice consumi ... | 1998 | 9919614 |
| structures of new acylated oleanene-type triterpene oligoglycosides, theasaponins e1 and e2, from the seeds of tea plant, camellia sinensis (l.) o. kuntze. | two new acylated oleanene-type triterpene oligoglycosides, theasaponins e1 and e2, were isolated from the seeds of tea plant [camellia sinensis (l.) o. kuntze]. the structures of theasaponins e1 and e2 were elucidated on the basis of chemical and physicochemical evidence to be expressed as 21-o-angeloyl-22-o-acetyltheasapogenol e 3-o-[beta-d-galactopyranosyl(1-->2])[beta-d-xylopyranosyl(1-->2)-alpha-l - arabinopyranosyl (1-->3)]-beta-d-glucopyranosiduronic acid and 21-o-angeloyl-28-o-acetyltheas ... | 1998 | 9880909 |
| clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis. | black tea is known to be a potent inhibitor of intestinal absorption of non-haem iron at least in healthy subjects. | 1998 | 9824354 |
| the effects of black tea and other beverages on aspects of cognition and psychomotor performance. | nineteen healthy volunteers ingested 400 ml black tea, coffee, caffeinated water, decaffeinated tea or plain water on three occasions through the day (0900, 1400 and 1900 hours). a 2 x 2 factorial design with caffeine (0, 100 mg) and beverage type (water, tea) was employed, with coffee (100 mg caffeine) as a positive internal control, based on a five-way crossover. a psychometric test battery comprising critical flicker fusion (cff), choice reaction time (crt), short-term memory (stm) and subjec ... | 1998 | 9784078 |
| effect of green and black tea supplementation on lipids, lipid oxidation and fibrinogen in the hamster: mechanisms for the epidemiological benefits of tea drinking. | there is considerable epidemiological evidence that tea drinking lowers the risk of heart disease. however, the mechanism by which tea can be protective is unknown. hamsters were fed a normal or high cholesterol diet for 2 weeks and drank green or black tea ad libitum. the plasma lipid profile was significantly improved by both teas compared to controls. also in vivo lipid oxidation as measured by plasma lipid peroxides and ldl+vldl oxidizability were significantly decreased by the teas. in the ... | 1998 | 9738930 |
| [flavonols, flavone and anthocyanins as natural antioxidants of food and their possible role in the prevention of chronic diseases]. | flavonoids are non-nutritive compounds of plants that have been intensively investigated during the past years due to their possible protective effects against chronic diseases. in vitro studies were able to demonstrate for flavonols, flavones, and most recently also for anthocyanins a considerable antioxidative activity, mainly based on scavenging of oxygen radicals. flavonols and anthocyanins are commonly found in european fruits and vegetables. in addition, black tea and red wine may have a h ... | 1998 | 9698642 |
| hplc method for evaluation of the free radical-scavenging activity of foods by using 1,1-diphenyl-2-picrylhydrazyl. | an hplc method for evaluation of the free radical-scavenging activity of foods by using 1,1-diphenyl-2-picrylhydrazyl (dpph) is reported. the activity was evaluated by measuring the decrease of dpph detected at 517 nm. by using this novel method, we determined the free radical-scavenging activity of several antioxidants: ascorbic acid, alpha-tocopherol, trolox, and cysteine. the results gave good correlation between the radical-scavenging activity determined by hplc and by conventional colorimet ... | 1998 | 9692204 |
| tea and coffee consumption and risk of colon and rectal cancer in middle-aged finnish men. | the association between coffee and black tea consumption and the subsequent risk of colon and rectal cancer was investigated within a finnish clinical trial cohort. one hundred eleven cases of colon cancer and 83 cases of rectal cancer were diagnosed over a median of 9.0 years of follow-up. proportional hazards regression models were used to derive adjusted relative risk (rr) and 95% confidence intervals (ci) for the association between coffee and tea consumption and cancer incidence. after cont ... | 1998 | 9682247 |
| plasma concentrations and urinary excretion of the antioxidant flavonols quercetin and kaempferol as biomarkers for dietary intake. | flavonols are antioxidants that may reduce the risk of heart disease. two major flavonols in the diet are quercetin and kaempferol, and their main sources in the netherlands are tea and onions. we investigated whether plasma concentrations and urinary excretion of quercetin and kaempferol in humans could be used as biomarkers of intake. we provided 15 subjects with strong black tea (1600 ml/d) or fried onions (129 g/d) for 3 d each in random order separated by a 4-d washout period. the tea provi ... | 1998 | 9665097 |
| bioavailability of catechins from tea: the effect of milk. | to assess the blood concentration of catechins following green or black tea ingestion and the effect of addition of milk to black tea. | 1998 | 9630386 |
| no effect of consumption of green and black tea on plasma lipid and antioxidant levels and on ldl oxidation in smokers. | intake of flavonoids is associated with a reduced cardiovascular risk. oxidation of ldl is a major step in atherogenesis, and antioxidants may protect ldl from oxidation. because tea is an important source of flavonoids, which are strong antioxidants, we have assessed in a randomized, placebo-controlled study the effect of consumption of black and green tea and of intake of isolated green tea polyphenols on ldl oxidation ex vivo and on plasma levels of antioxidants and lipids. healthy male and f ... | 1998 | 9598844 |
| mass spectrometry of selected components of biological interest in green tea extracts. | mass spectrometric methods including eims, fabms, and lc/esims have been surveyed as tools for the detection of catechins in extracts of green tea (camellia sinensis). eims provide both molecular weight and structure information, including epimer differentiation, on compounds 1, 2, and 4 and some structural information with compounds 5 and 6. fabms gives both molecular weight and structure information, by an retro-diels-alder mechanism, on all compounds. lc/esims provides unambiguous molecular w ... | 1998 | 9584400 |
| black tea consumption does not protect low density lipoprotein from oxidative modification. | to investigate the in vivo and in vitro effects of black tea on the oxidative modification of low density lipoprotein (ldl). | 1998 | 9537306 |
| apolipoprotein e genotype modulates the effect of black tea drinking on blood lipids and blood coagulation factors: a pilot study. | apolipoprotein e (apoe) genotype was determined in sixty-five subjects who had taken part in a 4-week randomized crossover trial to compare the effect of six mugs of black tea per day v. placebo on blood lipids and blood coagulation factors. four apoe genotype variants (seven e2/e3, forty-five e3/e3, twelve e3/e4 and one e4/e4) were found. apoe allele frequency was within the range typical for caucasian populations (apoe-e2 5.4%; apoe-e3 83.8%; apoe-e4 10.8%). individuals bearing at least one e4 ... | 1998 | 9536857 |
| association of coffee, green tea, and caffeine intakes with serum concentrations of estradiol and sex hormone-binding globulin in premenopausal japanese women. | caffeine intake has been proposed to influence breast cancer risk. its effect may be mediated by hormonal changes. the relationships between caffeine-containing beverages (coffee, green tea, black tea, oolong tea, and cola) and serum concentrations of estradiol and sex hormone-binding globulin were evaluated in 50 premenopausal japanese women. intakes of caffeine and caffeine-containing beverages were assessed by a semiquantitative food-frequency questionnaire. blood samples were obtained from e ... | 1998 | 9507508 |
| selection of column and gradient elution system for the separation of catechins in green tea using high-performance liquid chromatography. | a study of a variety of stationary phases and elution conditions for the liquid chromatographic (lc) determination of six biologically active green tea catechins has resulted in the development of two well-defined, reproducible systems for such analyses which overcome limitations of previously described methods. comparison of six reversed-phase columns indicates that deactivated stationary phases, which utilize ultrapure silica and maximize coverage of the silica support, provide significantly i ... | 1998 | 9474785 |
| identification of beverages and beverage stains by gc/ms using aroma components as indicators. | a method to identify brown coloured beverages or beverage stains for criminological purposes was devised using aroma components as indicators. the examined beverages comprised three brands each of beer, coffee, cola and black tea, two brands of oolong tea, and four brands of green tea. aroma components in each sample were efficiently concentrated with a porous polymer beads column (porapak q) and were analyzed by gas chromatography/mass spectrometry (gc/ms) using n-octyl alcohol as the internal ... | 1998 | 9457532 |
| isolation of an aroma precursor of benzaldehyde from tea leaves (camellia sinensis var. sinensis cv. yabukita). | the cyanoglycoside, prunasin, was isolated for the first time as an aroma precursor of benzaldehyde from fresh tea leaves (camellia sinensis var. sinensis cv. yabukita). prunasin was readily hydrolyzed by a crude enzyme prepared from the fresh tea leaves to liberate benzaldehyde. the isomerization of prunasin under neutral conditions was also recognized. | 1998 | 27385456 |
| effects of lifestyle and genetic polymorphisms on consumption of coffee or black tea and urinary caffeine levels. | to find the cause of individual differences in caffeine intake and its metabolism, we investigated the effects of lifestyle and genetic polymorphisms of caffeine metabolic enzymes on coffee or black tea and urinary caffeine levels among 259 male japanese. it was seen that cigarette smokers drank more coffee or black tea than non-smokers (p < 0.001). there was an inverse correlation between the amount of coffee or black tea consumed and age or the frequency of alcohol drinking (p < 0.05). genetic ... | 1998 | 23899363 |
| fluoride in tea--its dental significance: a review. | it has long been accepted that fluoride accumulates in the leaves of the tea plant. camellia sinensis. in addition it is known that some of this fluoride is released into the infusion which is drunk as tea. the exact concentration of fluoride in a cup of tea and the effects of this fluoride have been the subject of many international studies. this review summarizes the main points of such studies which have been carried out in an attempt to establish the dental significance of fluoride in tea. t ... | 1998 | 10530119 |
| effects of tea polyphenols and flavonoids on liver microsomal glucuronidation of estradiol and estrone. | administration of 0.5 or 1% lyophilized green tea (5 or 10 mg tea solids per ml, respectively) as the sole source of drinking fluid to female long-evans rats for 18 days stimulated liver microsomal glucuronidation of estrone, estradiol and 4-nitrophenol by 30-37%, 15-27% and 26-60%, respectively. oral administration of 0.5% lyophilized green tea to female cd-1 mice for 18 days stimulated liver microsomal glucuronidation of estrone, estradiol and 4-nitrophenol by 33-37%, 12-22% and 172-191%, resp ... | 1998 | 9605416 |
| tea and tea polyphenols inhibit cell hyperproliferation, lung tumorigenesis, and tumor progression. | both green and black tea have been shown to inhibit lung tumorigenesis in laboratory animal experiments. green tea inhibited n-nitrosodiethylamine-induced lung tumor incidence and multiplicity in female a/j mice when tea was given either during the carcinogen treatment period or during the post-carcinogen treatment period. in a separate tumorigenesis model, both decaffeinated black tea and decaffeinated green tea inhibited 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (nnk)-induced lung tumor f ... | 1998 | 9659588 |
| antimutagenic activity of tea towards 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline: effect of tea concentration and brew time on electrophile scavenging. | green tea and black tea inhibit colon carcinogenesis in rats exposed to the cooked meat-derived mutagen 2-amino-3-methylimidazo[4, 5-f]quinoline (iq). the present study compared the inhibitory activities of green tea and black tea towards a direct-acting mutagenic metabolite of iq, namely 2-hydroxyamino-3-methylimidazo[4, 5-f]quinoline (n-hydroxy-iq), under various brewing conditions. the following observations were made: (a) green tea (sencha midoriiro) and black tea (english breakfast tea) bre ... | 1998 | 9675318 |
| worldwide prevention of cancer and other chronic diseases based on knowledge of mechanisms. | international research, particularly as part of us/japan programs, has led to major advances in knowledge of causes of heart disease, stroke, many types of cancer and diabetes, showing that individual lifestyle is associated with these diseases. in japan, a major health problem is high blood pressure and stroke, and cancer of the stomach, from excessive use of salt and salted, pickled foods, and the relative low intake of protective fruits and vegetables. we identified a likely gastric carcinoge ... | 1998 | 9675332 |
| effect of black tea polyphenols on plasma lipids in cholesterol-fed rats. | the influence of black tea polyphenols on plasma lipid levels was investigated in rats fed a 15% lard and 1% cholesterol diet. the diet was supplemented with 1% black tea polyphenols extracted and condensed from black tea. rats fed the lard-cholesterol diet showed an increase in plasma cholesterol and liver lipids compared to rats fed a basal diet. the supplementation of black tea polyphenols in this lard-cholesterol diet decreased the lipid levels in the plasma and increased the fecal excretion ... | 1998 | 9675714 |
| black tea and mammary gland carcinogenesis by 7,12-dimethylbenz[a]anthracene in rats fed control or high fat diets. | epidemiological studies suggest that tea may reduce cancer risk, and in laboratory rodents, chemopreventive effects of tea or purified extracts of tea have been demonstrated in lung, gastrointestinal tract and skin. there is some evidence of chemoprevention by tea in the mammary gland, but the data are not conclusive. in order to evaluate more fully the possible influence of black tea on 7,12-dimethylbenz[a]anthracene (dmba)-induced mammary gland tumors in the female s-d (sprague-dawley) rat, th ... | 1998 | 9683188 |
| bulk acoustic wave bacterial growth sensor applied to analysis of antimicrobial properties of tea. | a bulk acoustic wave (baw) bacterial growth sensor has been proposed for study of inhibitory effects of tea by continuous monitoring of disturbances in proteus growth in the aqueous extracts of various teas, e.g. green tea, fuzhuan brick tea, oolong tea, kudin tea, and black tea. the kinetic parameters, e.g. asymptote (a), maximum specific growth rate (microm), lag time (lambda), and generation time (g), accurately estimated by using the growth response model, have been first used to characteriz ... | 1998 | 9694687 |
| potent suppressive activity of pheophytin a and b from the non-polyphenolic fraction of green tea (camellia sinensis) against tumor promotion in mouse skin. | chlorophyll-related compounds pheophytin a and b have been recently identified as antigenotoxic substances in the non-polyphenolic fraction of green tea (camellia sinensis), which suppressed umu c gene expression in tester bacteria induced by various genotoxins (okai and higashi-okai, cancer lett. 118 (1997) 117-123). in the present study, the authors analyzed in vivo and in vitro effects of pheophytin a and b from the non-polyphenolic fraction of green tea on tumor promotion in mouse skin as fo ... | 1998 | 9719465 |
| contribution of caffeine and flavanols in the induction of hepatic phase ii activities by green tea. | aqueous extracts of green tea, at concentrations of 2.5. 5.0 and 7.5%, were administered to rats as the sole drinking fluid for 4 weeks. hepatic glutathione s-transferase (gst) activity, determined using 1-chloro-2,4-dinitrobenzene (cdnb) and 3,4-dichloronitrobenzene (dcnb) as substrates, and udp-glucuronosyl transferase activity, determined using 2-aminophenol as substrate, were induced but the effect was not always dose dependent. at the two highest doses, hepatic catalase activity was inhibit ... | 1998 | 9734711 |
| the effect of a component of tea (camellia sinensis) on methicillin resistance, pbp2' synthesis, and beta-lactamase production in staphylococcus aureus. | extracts of tea (camellia sinensis) can reverse methicillin resistance in methicillin-resistant staphylococcus aureus (mrsa) and also, to some extent, penicillin resistance in beta-lactamase-producing s. aureus. these phenomena are explained by prevention of pbp2' synthesis and inhibition of secretion of beta-lactamase, respectively. synergy between beta-lactams and tea extracts were demonstrated by disc diffusion, chequerboard titration and growth curves. partition chromatography of an extract ... | 1998 | 9738838 |
| dietary antioxidants inhibit development of fatty streak lesions in the ldl receptor-deficient mouse. | oxidized low density lipoprotein (ldl) promotes atherogenesis. although pharmacological antioxidants such as probucol inhibit both ldl oxidation and atherosclerosis in hyperlipidemic animals, the effects of natural antioxidants such as vitamin e are inconclusive. to further determine the effects of supplemental dietary antioxidants in vivo, we evaluated whether combined dietary antioxidants (0.1% vitamin e, 0.5% beta-carotene, and 0.05% vitamin c) inhibit ldl oxidation and fatty streak lesion de ... | 1998 | 9743241 |
| inhibition of lung carcinogenesis by black tea in fischer rats treated with a tobacco-specific carcinogen: caffeine as an important constituent. | here, we examined the effect of black tea and caffeine on lung tumorigenesis in f344 rats induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (nnk) in a 2-year bioassay. nnk was administered s.c. at a dose of 1.5 mg/kg body weight three times weekly for 20 weeks. animals were given either black tea as drinking water at concentrations of 2%, 1%, or 0.5%, or caffeine in drinking water at concentrations identical to those in 2% and 0.5% tea infusions for 22 wee ... | 1998 | 9751618 |
| potent suppressive activity of chlorophyll a and b from green tea (camellia sinensis) against tumor promotion in mouse skin. | potent antigenotoxic and anti-tumor promoting activities of chlorophyll a from green tea (camellia sinensis) have been shown using in vitro cell culture experiments (okai y. et al. (1996) mutation res., 370, 11-17). in the present study, the authors analyzed in vivo effects of chlorophyll a and b from green tea on tumor promotion in mouse skin in the following ways. 1. when chlorophyll a and b from green tea were applied before each treatment by a tumor promoter, 12-o-tetradecanoyl-phorbol-13-ac ... | 1998 | 9760704 |
| an in vitro study of theaflavins extracted from black tea to neutralize bovine rotavirus and bovine coronavirus infections. | crude theaflavin was extracted from black tea and then fractionated by hplc into five components (initial peaks (ip), tf1, tf2a, tf2b, and tf3). the crude extract and the various fractions of theaflavin were collected and tested, individually and in combination, for antirotaviral activity. the mean effective concentration (ec50) was calculated and compared. activity varied from the most active being the uncharacterized theaflavin-like initial peaks (ip) with an ec50 of 0.125 microgram/ml to the ... | 1998 | 9850995 |
| black tea theaflavins induce programmed cell death in cultured human stomach cancer cells. | the exposure of human stomach cancer kato iii cells to black tea theaflavin extract, free theaflavin, and theaflavin digallate that are main components of the extract, led to both growth inhibition and the induction of programmed cell death (apoptosis). morphological changes showing apoptotic bodies were observed in the cells treated with black tea theaflavin extract, theaflavin and theaflavin digallate. the fragmentations by these theaflavin compounds of dna to oligonucleosomal-sized fragments ... | 1998 | 9852288 |
| protective action of plant polyphenols on radiation-induced chromatid breaks in cultured human cells. | the present study was performed to determine whether plant polyphenols can protect human cells against radiation-induced dna damage manifested as chromatid breaks. since each chromatid contains a single continuous molecule of double stranded dna, chromatid breaks represent unrepaired dna strand breaks. the addition of green or black tea extracts, their polyphenols or curcumin to cultures of human skin fibroblasts or pha-stimulated blood lymphocytes significantly reduced the frequencies of radiat ... | 1998 | 9858893 |
| contribution of theafulvins to the antimutagenicity of black tea: their mechanism of action. | theafulvins were isolated from black tea aqueous infusions and their antimutagenic activity was evaluated against a number of food carcinogens. theafulvins gave rise to a concentration-dependent inhibition of the mutagenicity of 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, benzo[a]pyrene, 7,12-dimethylbenz[a]anthracene, nitrosopyrrolidine and nitrosopiperidine, but, in contrast, the mutagenicity of aflatoxin b1 was enhanced. the mutagenicity exhibite ... | 1998 | 9862196 |
| role of glutathione in the antiulcer effect of hot water extract of black tea (camellia sinensis). | the role of a hot water extract of black tea (camellia sinensis (l). o. kuntze theaceae) in the gastric cytoprotective mechanisms was studied using gastric mucosal lesions produced by various ulcerogens in rats as an experimental model. prior oral administration of black tea extract (bte) at 20 ml/kg, i.g. once a day for 7 days significantly reduced the incidence of gastric erosions and severity induced by ethanol, diethyldithiocarbamate (ddc) and diethylmaleate (dem). this treatment also favora ... | 1998 | 9869262 |
| antibacterial activity of camellia sinensis extracts against dental caries. | different bacteria were separated from saliva and teeth of cariogenic patients and identified by a variety of morphological and biochemical tests. extracts of green tea strongly inhibited escherichia coli, streptococcus salivarius and streptococcus mutans. the antibacterial effect of green and black tea extracts were compared with those of amoxicillin, cephradine and eugenol. | 1998 | 9875456 |
| effect of green tea and black tea on the metabolisms of mineral elements in old rats. | a 2-mo experiment with the white sprague-dawley (sd) rats was conducted to investigate the effect of the water extracts of black tea (btwe) and green tea (gtwe) and the black tea leaves (btf) and the green tea leaves (gtf) on the metabolism of mineral elements. one hundred eight 12-mo-old white sd rats were randomly divided into 13 groups; 6 of these drank the btwe or gtwe in which the water extracts concentrations of black tea or green tea were, respectively, 0.6%, 1.2%, and 2.4%, and 6 of thes ... | 1998 | 9877538 |
| effects of tea infusions of various varieties or different manufacturing types on inhibition of mouse mast cell activation. | we investigated effects of various tea infusions on mast cell activation using mouse mast cells. among various tea extracts, infusions from cultivar 'benihomare' and taiwan lineage strongly inhibited histamine release after fc epsilon ri cross-linking. among three types of tea (from cultivar 'benihomare'), extract from oolong tea or black tea inhibited histamine release more strongly than green tea extract. furthermore, 'benihomare' oolong tea extract suppressed tyrosine phosphorylation of cellu ... | 1998 | 9972253 |
| chemopreventive effects of black tea polyphenols in mouse skin model of carcinogenesis. | in the present investigations, the antitumorigenic effect of black tea polyphenols (btp) in two-stage mouse skin model of carcinogenesis was studied. the animals were initiated with a single "subcarcinogenic" topical dose (52 micrograms/200 microliters acetone) of 7, 12-dimethylbenzanthracene (dmba). to evaluate the anti-tumour initiating activity, btp was topically applied twice a week for three weeks prior to dmba application, followed by topical treatment with 12-o-tetradecanoyl phorbol-13-ac ... | 1998 | 10095927 |
| isolation and identification of acetyl-coa carboxylase inhibitors from green tea (camellia sinensis). | an aqueous methanol extract from green tea showed potent acetyl-coa carboxylase inhibitory activity. an active compound was isolated from the extract and identified as (-)-epigallocatechin gallate by instrumental analyses. the ic50 value of (-)-epigallocatechin gallate was 3.1 x 10(-4) m. among tea catechins and related compounds, nearly equal activity was found in (-)-epigallocatechin gallate and (-)-epicatechin gallate, whereas (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, gallic acid a ... | 1998 | 9571782 |
| inhibition of salivary amylase by black and green teas and their effects on the intraoral hydrolysis of starch. | tea decoctions prepared from a number of black and green teas inhibited amylase in human saliva. black teas gave higher levels of inhibition than green teas, and removal of tea tannins with gelatin led to the loss of inhibitory activity from all decoctions. streptococcal amylase was similarly inhibited by tea decoctions. fluoride was without effect on amylase. since salivary amylase hydrolyzes food starch to low molecular weight fermentable carbohydrates, experiments were carried out to determin ... | 1998 | 9577990 |
| screening of potential cancer preventing chemicals for induction of glutathione in rat liver cells. | with brl 3a hepatocytes, a series of selected, potentially chemopreventive chemicals was evaluated for their capacity to elevate glutathione (gsh) levels. since sodium selenite consistently increased gsh levels by approximately 70%, it was selected as a positive control. of 62 test chemicals, eighteen stimulated gsh levels by >30%, but eleven of these had only a modest effect or displayed considerable toxicity. at non-toxic concentrations, seven compounds had substantial activity: black tea extr ... | 1998 | 9468590 |
| effect of black tea on azoxymethane-induced colon cancer. | two sets of experiments on the role of tea in azoxymethane (aom) induced colon cancer were performed. the first test involved male f344 rats given 1.25% solutions of black tea beginning at 5 weeks of age and ending at 51 days of age. at 6 and 7 weeks of age, they received 15 mg/kg aom and were held for 50 weeks. another group received the aom dosage at 6 and 7 weeks and were placed on the tea solutions 2 days after the last aom dosage, at 51 days of age, and held for the 50-week period. the end ... | 1998 | 9472717 |
| effects of japanese black tea on atherosclerotic disorders. | the atherogenic index was found to be significantly better in rats fed a high-cholesterol diet supplemented with black tea extract than in the ones not given the extract. it was also evident that black tea inhibited the proliferation of smooth muscle cells involved in the development and progression of atherosclerosis, and suppressed the production of oxidized low-density lipoprotein, a cause of lipid accumulation. it thus seems likely that black tea has an antiatherosclerotic action. | 1998 | 9501517 |
| inhibition of n-nitrosation of secondary amines in vitro by tea extracts and catechins. | inhibition of nitrite-mediated n-nitrosation of dimethylamine, morpholine and n-methylaniline by tea extracts and by 6 individual catechins in the extracts was studied. the inhibitions were detected by quantifying the nitrosamines formed. eight different kinds of teas (5 green teas, a roasted green tea, an oolong tea, and a black tea) were examined for their inhibitory abilities and for their catechin contents, with an attempt to correlate the inhibitory activities to the catechin contents. the ... | 1998 | 9508368 |
| effect of tea on the formation of dna adducts by azoxymethane. | 1. the effect of black tea on the conversion of azoxymethane (aom) to dna reactive metabolites was studied in four groups of the male f344 rat. each received 1.25% solutions of tea for 2 or 6 weeks, and simultaneous controls drank water. all rats were injected s.c. twice with 15 mg/kg aom after the first or fifth week respectively, on tea or water, and again 1 week later. groups were killed 6 h after the last dose, or 18 h later. the liver and colon were rapidly removed and rinsed with buffer so ... | 1998 | 9522444 |
| inhibition of spontaneous formation of lung tumors and rhabdomyosarcomas in a/j mice by black and green tea. | we investigated the effects of black tea (bt) and green tea (gt) infusion on the spontaneous formation of lung tumors and rhabdomyosarcomas in a/j mice. female a/j mice, 6 weeks of age, were allocated into five groups (50 per group) and were given the following as the sole source of drinking fluid: (i) deionized water (control group), (ii) 0.5% bt, (iii) 1% bt, (iv) 2% bt and (v) 1% gt. after 60 weeks, the mice were killed by decapitation. lung tumor incidence, multiplicity and volume were signi ... | 1998 | 9525286 |
| protective role of black tea against oxidative damage of human red blood cells. | the purpose of our study was to explore the possible scavenging property of black tea and catechins, the major flavonols of tea-leaf, against damage by oxidative stress. for this purpose, human red blood cell (rbc) was taken as the model and the oxidative damage was induced by a variety of inducers, e.g. phenylhydrazine (phx), cu(2+)-ascorbic acid, and xanthine/xanthine oxidase systems. lipid peroxidation of pure erythrocyte membrane and of whole red blood cell could be completely prevented by b ... | 1998 | 9535765 |
| consumption of tea and coffee and the risk of lung cancer in cigarette-smoking men: a case-control study in uruguay. | this study investigated the effect of drinking tea or coffee on the lung cancer risk of male cigarette smokers in a case-control in uruguay. four hundred and twenty-seven lung cancer cases were frequency matched on age and residence with 428 hospitalized controls suffering from conditions unrelated to tobacco smoking and diet. whereas coffee drinking had no effect on the lung cancer risk of the cigarette-smoking men in this study, black tea consumption decreased this risk. heavy drinkers of tea ... | 1998 | 9567246 |
| ntp toxicology and carcinogenesis studies of theophylline (cas no. 58-55-9) in f344/n rats and b6c3f1 mice (feed and gavage studies). | theophylline is an alkaloid found in tea (thea sinensis) and chocolate and is structurally related to caffeine and theobromine. theophylline is used as a pharmaceutical agent. it stimulates the heart and central nervous system, relaxes the smooth muscles of the bronchi and blood vessels, and causes diuresis. the drug is used mainly as a bronchodilator in obstructive airway diseases, such as bronchial asthma, and for myocardial stimulation. theophylline was nominated for toxicologic and carcinoge ... | 1998 | 12571677 |
| potent suppressing activity of the non-polyphenolic fraction of green tea (camellia sinensis) against genotoxin-induced umu c gene expression in salmonella typhimurium (ta 1535/psk 1002)--association with pheophytins a and b. | antigenotoxic and antimutagenic activities of green tea extract and tea-derived polyphenols have been studied using in vitro and in vivo experiments. however, antigenotoxic substances in the non-polyphenolic fraction of green tea have been poorly elucidated. in the present study, the effect of the non-polyphenolic fraction of green tea on genotoxin-induced umu c gene expression was analyzed using a tester bacteria, and potent antigenotoxic substances in the non-polyphenolic fraction were identif ... | 1997 | 9570394 |
| potent suppressive activity of nonpolyphenolic fraction of green tea (camellia sinensis) against genotoxin-induced umu c gene expression in salmonella typhimurium (ta 1535/psk 1002), tumor promotor-dependent ornithine decarboxylase induction of balb/c 3t3 fibroblast cells, and chemically induced mouse skin tumorigenesis. | many experimental studies for anticarcinogenic activity of green tea (camellia sinensis) and tea-derived polyphenols have been carried out. however, the anticarcinogenic activity of the nonpolyphenolic fraction of green tea has been poorly elucidated. to study this problem, the effect of the nonpolyphenolic fraction of green tea leaves was analyzed using in vitro and in vivo experiments associated with tumor initiation and promotion as follows: 1) the nonpolyphenolic fraction caused a strong sup ... | 1997 | 9485539 |
| tea and cancer prevention: an evaluation of the epidemiologic literature. | animal and in vitro studies provide evidence of an anticarcinogenic potential of active ingredients in teas. this review encompasses epidemiologic studies of stomach, colon, and lung cancer as well as the evidence of a relationship between tea drinking and cancer at large in humans. cohort studies do not suggest a protective role for tea drinking in the total risk of cancer. site-specific studies reveal a more complex picture. the epidemiologic studies on tea drinking and stomach cancer do not j ... | 1997 | 8970175 |
| tea antioxidants in cancer chemoprevention. | in recent years, the concept of cancer chemoprevention has matured greatly. significant reversal or suppression of premalignancy in several sites by chemopreventive agents appears achievable. this article summarizes experimental data on chemopreventive effects of tea polyphenols in different tumor bioassay systems. tea (camellia sinensis) is cultivated in about 30 countries, and is the most widely consumed beverage in the world. three main commercial tea varieties--green, black, and oolong--are ... | 1997 | 9591194 |
| comparison of metabolic effects of vegetables and teas with colorectal proliferation and with tumour development in dmh-treated f344 rats. | the aim of this study was to screen potentially chemopreventive vegetables and teas for their effects as human dietary components for the colorectal epithelium and also to seek biomarkers of preventive efficacy. groups of f344 rats were adapted to a human basal diet supplemented with vegetables or teas, having known contents of glucosinolates, polyphenols and anti-oxidants. both inductions and suppressions were found for overall glutathione s-transferase (gst) and quinone reductase activities. t ... | 1997 | 9103311 |
| tea, or tea and milk, inhibit mammary gland and colon carcinogenesis in rats. | research was performed on the effect of tea, or tea and milk, instead of drinking water, in rat models of cancer in the mammary gland or colon. solutions of 1.25% (w/v) black tea, or 1.85% (v/v) milk in tea were prepared three times per week. sd rats were given tea beginning at 42 days of age; one group was gavaged 5 mg 7,12-dimethylbenz[a]anthracene (dmba) at 49 days of age; another group received 8.4 mg 2-amino-3-methylimidazo[4,5-f]quinoline (iq) twice per week beginning at age 49, then 14 mg ... | 1997 | 9103322 |
| characterization of early pulmonary hyperproliferation and tumor progression and their inhibition by black tea in a 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis model with a/j mice. | the pathogenesis of pulmonary tumors induced by a tobacco carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (nnk), and its inhibition by black tea have been characterized. female a/j mice (6 weeks old) were treated with a single dose of nnk (103 mg/kg of body weight, i.p.) on day 0, and the cell proliferation index was measured by the incorporation of bromodeoxyuridine (brdurd) immunohistochemically. the number of brdurd-labeled cells increased in the bronchiolar epithelium from day 2 t ... | 1997 | 9157981 |
| herbal teas and populace health care in tropical china. | commercial chinese herbal tea is the development of the populace in tropical and subtropical china consequential to their fight against infectious diseases and their struggle to explore local plants to relieve fever, to alleviate pain, to restore strength and to modulate immunity against viral epidemics. from these ethnomedical experiences, two types of herbal teas were commercialized, namely, liangcha and medicated teas. liangcha refers to a ready-made decoction infused from wild plants served ... | 1997 | 9167003 |
| anti-allergic effect of tea-leaf saponin (tls) from tea leaves (camellia sinensis var. sinensis). | we investigated the anti-allergic effect of tea-leaf saponin (tls), which was a mixture of saponins separated from the leaves of camellia sinensis var. sinensis, in guinea pigs and rats. tls (20-100 mg/kg) dose-dependently inhibited experimentally-induced asthma, and id50 was 61.7 mg/kg. tls (20-100 mg/kg) dose-dependently inhibited a 48 h homologous pca (passive cutaneous anaphylaxis) reaction, and the inhibitory effect was similar to that of tranilast. tls (1-100 microg/ml) also inhibited the ... | 1997 | 9178940 |
| chemoprotection against the formation of colon dna adducts from the food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (phip) in the rat. | the mutagenic heterocyclic aromatic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (phip), is a pyrolysis product in cooked foods that has been shown to be a rat colon carcinogen and has been implicated in the etiology of human colon cancer. in order to identify chemoprotection strategies that could be carried out in humans, a pilot study was conducted in which phip-dna-adduct levels were quantified in the colons of male f344 rats that had been subjected to 16 different putative chemopro ... | 1997 | 9202746 |
| anti-human immunodeficiency virus activity of oligosaccharides from rooibos tea (aspalathus linearis) extracts in vitro. | the active substances, acid polysaccharides, were extracted with 1% sodium hydroxide from the leaves of rooibos tea (aspalathus linearis), du zhong cha (eucommia ulmoides oliv.) and japanese tea leaves (camellia sinensis var. sinensis). the alkaline extracts of rooibos tea and du-zhong tea leaves, but not japanese tea leaves suppressed the hiv-induced cytopathicity using hiv (htlv-iii) infected mt-4 cells, having extremely low cytotoxicity: its 50% effective concentration (ec50) was 12-67 microg ... | 1997 | 9209319 |
| microbiological activity of whole and fractionated crude extracts of tea (camellia sinensis), and of tea components. | aqueous extracts of teas (camellia sinensis) of different types and from various sources inhibited a wide range of pathogenic bacteria, including methicillin-resistant staphylococcus aureus. tea extracts were bactericidal to staphylococci and yersinia enterocolitica at well below 'cup of tea' concentrations. activity was confined to one of four fractions obtained from a green tea extract by partition chromatography. testing of pure tea compounds and closely related chemicals suggested that the a ... | 1997 | 9228784 |
| [prophylactic effect of black tea extract as gargle against influenza]. | we examined whether gargling with black tea prevents influenza infection. tests were carried out during a five month period (october 1992 to march 1993). the control group that followed their normal daily routine, whereas the test group that gargled with 0.5 w/v% black tea extract twice daily (at 8 a.m. and 5 p.m.). influenza viruses were isolated from influenza patients and an antigen analysis was carried out. as a result, two strains of influenza a viruses (h3n2) and ten strains of b virus wer ... | 1997 | 9248263 |
| polyphenols as inhibitors of carcinogenesis. | many polyphenolic compounds have demonstrated anticarcinogenic activities in animal models. these compounds include flavanone, flavonols, isoflavone, and catechins. in this article, tea catechins will be used as an example to illustrate current research in this area. many laboratory studies have demonstrated the inhibition of tumorigenesis in animal models by different tea preparations. the animal models include tumorigenesis in the mouse lung, rat and mouse esophagi, mouse forestomach, mouse sk ... | 1997 | 9255589 |
| [effect of tea extracts, catechin and caffeine against type-i allergic reaction]. | the antiallergic effects of green tea, oolong tea, and black tea extracts by hot water were examined. these extracts inhibited the passive cutaneous anaphylaxis (pca) reaction of rat after oral administration. three tea catechins, (--)-epigallocatechin (egc), (--)-epicatechin gallate (ecg), and (--)-epigallocatechin gallate (egcg) isolated from green tea showed stronger inhibitory effects than that of a green tea extract on the pca reaction. the inhibitory effects of egc and egcg on the pca reac ... | 1997 | 9261215 |
| inhibitory activity of green and black tea in a free radical-generating system using 2-amino-3-methylimidazo[4,5-f]quinoline as substrate. | green tea and black tea inhibit colon carcinogenesis in rats exposed to the cooked meat mutagen 2-amino-3-methylimidazo[4,5-f]quinoline (iq). in the present investigation, green tea, black tea and (-)-epigallocatechin gallate (egcg) were shown to block the production of oxygen free radicals derived from iq in the presence of nadph-cytochrome p450 reductase. in kinetic studies using iq as the substrate and dmpo as a free radical spin trap, egcg increased the k(m) of the reaction without altering ... | 1997 | 9263532 |
| effect of green tea (camellia sinensis) extract on the rat diaphragm. | the effect of hot water extract of green tea on skeletal muscle and its neurotransmission was studied employing innervated and denervated rat diaphragm. green tea extract (gte) has a facilitatory effect at lower concentrations and a paralytic effect at higher concentrations on skeletomotor function. gte did not have any effect on direct twitch responses or on acetylcholine (ach) and kcl induced contractures of denervated rat diaphragm and it antagonised the submaximal paralytic effect of d-tuboc ... | 1997 | 9292413 |
| effects of dietary consumption of black tea infusion alone and in combination with known clastogens on mouse bone marrow chromosomes in vivo. | black tea infusion in water, in concentrations simulating human consumption, was administered by gavage daily to male swiss mice for 7 days. one set was given tea once daily and the other twice daily. the mice were then exposed to two known clastogens: chromium (vi) as potassium dichromate and mitomycin c on day 7, and killed after 24 hr. chromosome damage was studied in preparations made from bone marrow following colchine injection of all mice, and examination of the cells after pretreatment i ... | 1997 | 9301648 |
| theophylline metabolism in higher plants. | metabolism of [8-(14)c]theophylline was investigated in leaf segments from camellia sinensis (tea), camellia irrawadiensis, ilex paraguariensis (maté) and avena sativa, root segments of vigna mungo seedlings and cell suspension cultures of catharanthus roseus. there was extensive uptake and metabolism of [8-(14)c]theophylline by leaves of tea and camellia irrawadiensis and, to a lesser extent, maté. these purine alkaloid-containing species converted [8-(14)c]theophylline into 3-methylxanthine, x ... | 1997 | 9305805 |
| inhibition of collagenases from mouse lung carcinoma cells by green tea catechins and black tea theaflavins. | theaflavin and theaflavin digallate, which are components of black tea were examined by in vitro invasion assay with mouse lewis lung carcinoma ll2-lu3 cells, which are highly metastatic. the compounds inhibited invasion by the tumor cells. gelatin zymography showed that the cells secreted matrix metalloproteinases (mmps), probably including mmp-2 and mmp-9, which may be involved in tumor cell invasion and metastasis. theaflavin and theaflavin digallate also inhibited mmps from the culture mediu ... | 1997 | 9339552 |
| some perspectives on dietary inhibition of carcinogenesis: studies with curcumin and tea. | topical application of curcumin inhibits chemically induced carcinogenesis on mouse skin, and oral administration of curcumin inhibits chemically induced oral, forestomach, duodenal, and colon carcinogenesis. curcumin and other inhibitors of cyclooxygenase and lipoxygenase are thought to inhibit carcinogenesis by preventing the formation of arachidonic acid metabolites. in contrast to our expectation of a tumorigenic effect of arachidonic acid, we found that treatment of 7,12-dimethylbenz[a]anth ... | 1997 | 9349692 |
| possible mechanisms of antimutagens by various teas as judged by their effects on mutagenesis by 2-amino-3-methylimidazo[4,5-f]quinoline and benzo[a]pyrene. | possible mechanisms of antimutagenicity of various tea extracts (green, pouchong, oolong and black tea) toward 2-amino-3-methylimidazo[4,5-f]quinoline (iq) and benzo[a]pyrene (b[a]p) were investigated using a salmonella/microsome assay. tea extracts exhibited no inhibitory effects toward iq and b[a]p in bio-antimutagenic assays, indicating that their antimutagenic activity is desmutagenic in nature. the mutagenicities of iq and b[a]p decreased as the reaction periods of tea extracts with promuta ... | 1997 | 9357568 |
| urine levels of aluminum after drinking tea. | a microwave-assisted acid digestion procedure coupled with a graphite furnace atomic absorption method has been applied in the determination of aluminum (al) in urine to verify the correlation of free forms of al in tea infusions and urinary excretion of al. significant urinary al excretion has been found in 24-h urine of four volunteers after tea drinking. however, the difference in amount of al excretion in urine between the consumption of oolong (black tea) and long-jin (green tea), each of t ... | 1997 | 9359993 |
| inhibition of phorbol ester tumor promoter 12-o-tetradecanoylphorbol-13-acetate-caused inflammatory responses in sencar mouse skin by black tea polyphenols. | over the past 10 years many studies from several laboratories defined anticarcinogenic and anti-inflammatory effects of tea, a widely consumed beverage by the human population. much of such work has been conducted with green tea or its polyphenolic constituents. regarding black tea, studies have shown that its water extract affords protection against tumor promotion caused by chemical carcinogens or ultraviolet b radiation in murine skin carcinogenesis models. several studies have shown that top ... | 1997 | 9363999 |