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PubMed2006

Iron availability and consumption of tea, vervain and mint during weaning in Morocco.

BACKGROUND/AIMS: Iron deficiency impairs growth and psychomotor development of infants. In Morocco, infusions are introduced very early in infant diet, and could contribute to iron deficiency, due to their high polyphenol content. METHODS: The availability of tea, mint and vervain infusions was assessed using an in vitro model of digestion and dialysis. Two gastric pHs were used: pH 4 as in the first week life, and pH 2.5 as in older infants. Six repetitions of each experiment were made. The total polyphenol content of infusions was measured. RESULTS: At pH 4 and at pH 2.5, iron availability was decreased by tea and vervain, and increased by mint and ascorbic acid. At both pHs it was increased by addition of ascorbic acid to tea and vervain. In addition, at pH 2.5 it was increased by addition of ascorbic acid to mint. The highest value was observed in the presence of both ascorbic acid and mint (33.1 +/- 4.1%). In any case, iron availability was higher at pH 2.5 than at pH 4 (with single compounds or combinations with ascorbic acid). The polyphenol contents (mg/l) of tea, vervain and mint infusions were 2,236.1, 771.1, and 16.5. CONCLUSIONS: Tea and vervain infusions inhibited iron availability. In contrast, mint improved it; vitamin C helped in preventing these inhibiting properties. It could be proposed to discourage tea and vervain drinking at early weaning and to replace them by mint infusion, or at least to promote the consumption of vitamin C-rich fruit juice to counteract these inhibiting effects.

Ascorbic Acid↗
PubMed1994

Effect of tea on iron absorption from the typical Tunisian meal 'couscous' fed to healthy rats.

Black and green tea decoctions are popular beverages in Tunisia, especially after eating. Our study was performed to examine the effect of graded amounts of black and green tea decoction prepared under realistic Tunisian conditions on nonheme iron absorption from a typical Tunisian meal, 'couscous', by extrinsic radioiron labeling in rats. Concentrations of 300, 200 and 100 micrograms/ml of black tea decreased dramatically nonheme iron bioavailability from couscous, but 50 micrograms/ml did not influence iron absorption. The inhibition of nonheme iron from couscous varied from 36 to 61% with black tea and 30.5% with green tea. Taken together, our findings show that the tea decoction in Tunisia has a great inhibitory power and may constitute an important factor for the development of iron deficiency anemia throughout Tunisia.

Absorption↗
PubMed1993

Oolong tea polyphenols inhibit experimental dental caries in SPF rats infected with mutans streptococci.

An extract of oolong tea (semifermented tea leaves of Camellia sinensis) and its chromatographically isolated polyphenolic compound was examined for in vitro inhibitory effects on glucosyltransferases (GTases) of mutans streptococci and on caries development in Sprague-Dawley rats infected with mutans streptococci. The samples showed no detectable effect on the growth of mutans streptococci. However, insoluble glucan synthesis from sucrose by the GTases of Streptococcus mutans MT8148R and Streptococcus sobrinus 6715 was markedly inhibited, as was sucrose-dependent cell adherence of these mutans streptococci. The administration of the oolong tea extract and the isolated polyphenol compound into diet 2000 and drinking water resulted in significant reductions in caries development and plaque accumulation in the rats infected with mutans streptococci. The active components in the oolong tea extract were presumptively identified as polymeric polyphenols which were specific for oolong tea leaves. These results indicate that the oolong tea polyphenolic compounds could be useful for controlling dental caries.

Animals↗
PubMed2005

The effects of green tea consumption on incidence of breast cancer and recurrence of breast cancer: a systematic review and meta-analysis.

BACKGROUND: Green tea is widely used by women for the prevention and treatment of breast cancer. The authors aimed to determine the efficacy of green tea ingestion on the risk of breast cancer development and the risk of breast cancer recurrence. METHODS: The authors conducted a systematic review and meta-analyses of observational studies from systematic searches of 8 electronic data sources and contact with authors. They included studies assessing breast cancer incidence and recurrence. RESULTS: Results: The pooled relative risk (RR) of developing breast cancer for the highest levels of green tea consumption in cohort studies was 0.89 (95% confidence interval [CI], 0.71-1.1; P= .28; I(2)= 0%), and in case control studies, the odds ratio was 0.44 (95% CI, 0.14-1.31; P= .14; I(2)= 47%). The pooled RR of cohort studies for breast cancer recurrence in all stages was 0.75 (95% CI, 0.47-1.19; P= .22; I(2)= 37%). A subgroup analysis of recurrence in stage I and II disease showed a pooled RR in cohort studies of 0.56 (95% CI, 0.38-0.83; P= .004; I2= 0%). Dose-response relationships were evident in only 3 of the 7 studies. CONCLUSION: To date, the epidemiological data indicates that consumption of 5 or more cups of green tea a day shows a non-statistically significant trend towards the prevention of breast cancer development. Evidence indicates that green tea consumption may possibly help prevent breast cancer recurrence in early stage (I and II) cancers. However, conclusions as to the potential therapeutic application of green tea are currently impossible to make due to the small number of studies conducted, the lack of any clinical trial evidence, the lack of a consistent dose-response relationship, and the potential for interaction with standard care.

Anticarcinogenic Agents↗
PubMed1999

Green tea and its major components ameliorate immune dysfunction in mice bearing Lewis lung carcinoma and treated with the carcinogen NNK.

The protective effects of tea and/or its components on dysfunction of immune functions during tumor growth and carcinogenesis in mice were studied using two experimental models: C57/BL6J mice transplanted with Lewis lung carcinoma (LLC) and Kunming mice treated with a single dose of 4-(methylnitrosamino-)-1-(3-pyridyl)-1-butanone (NNK). In C57/BL6J mice bearing LLC, the weight of the thymus decreased, the proportion of CD4(+)-positive T lymphocytes and the ratio of CD4+ to CD8+ decreased, luminol-enhanced chemiluminescence of white blood cells in peripheral blood stimulated by zymosan increased, and plaque-forming cells (PFC) decreased. However, in LLC-bearing mice given green tea as drinking water, all immune functions were improved, along with inhibition of tumor growth. In Kunming mice treated with NNK, during the four weeks of observation, their immunologic indicators, such as phagocytosis of macrophages in the abdominal cavity, luminol-enhanced chemiluminescence of white blood cells, plaque-forming cells, and delayed-type hypersensitivity, increased or decreased to various extents compared with normal controls. However, these changes were significantly prevented in the mice given green tea, mixed tea, or tea polyphenol as drinking water. In conclusion, tea and its components ameliorated immune dysfunction in mice bearing LLC or treated with the carcinogen NNK.

Animals↗
PubMed1999

Consumption of green tea causes rapid increase in plasma antioxidant power in humans.

Green tea contains polyphenolic antioxidants that have shown anticarcinogenic properties in animal and in vitro experimental studies. Current data regarding absorption and bioavailability of tea antioxidants in humans, however, are conflicting. In this study, plasma and urine antioxidant power after ingestion of green tea was measured using the ferric reducing/antioxidant power (FRAP) assay (US patent pending) to assess absorption, systemic distribution, and renal excretion of green tea antioxidants in healthy adults. Results showed that absorption of green tea antioxidants was rapid, with peak increase in plasma FRAP of around 4% at 40 minutes after ingestion: mean increase was 44 +/- 9 (SE) mumol/l. Excretion of polyphenolic antioxidants was also fast, peaking at 60-90 minutes, with significant correlation between urinary FRAP values and urinary total phenolic concentrations (r = 0.845, p < 0.001). In control studies, no increase in plasma or urine FRAP values was seen after intake of water. Although the amount of antioxidants absorbed was relatively small and the increase in plasma antioxidant power was of short duration, results demonstrate that some potentially anticarcinogenic polyphenolic antioxidants in green tea enter the systemic circulation soon after ingestion and cause a significant increase in plasma antioxidant status. This increase may, in turn, lower oxidative damage to DNA and so decrease risk of cancer.

Adult↗
PubMed2003

Tea beverage in chemoprevention of prostate cancer: a mini-review.

Because prostate cancer has a long latency period and is typically diagnosed in elderly men, it represents an ideal candidate disease for chemoprevention. Therefore, even a modest delay achieved through intervention could have a significant impact on the outcome of this disease. Epidemiological and laboratory studies have provided convincing evidence that diet, genetic factors, and lifestyle are major causes of prostate cancer. Although surgery, radiotherapy, and hormone therapy are the most widely accepted curative options for a selected group of patients suffering from prostate cancer, the side effects of these treatments are many. In recent years, many dietary agents have been being described that show a wide range of chemopreventive effects in cell culture and selected animal model systems of prostate carcinogenesis. One such agent is the beverage tea, which, next to water, is the most popularly consumed beverage in the world. The epidemiological studies and recent data, amassed from various laboratories around the world, provide evidence that tea polyphenols such as epigallocatechin-3-gallate, epigallocatechin, and epicatechin-3-gallate may have the potential to lower the risk of prostate cancer in the human population. Recently, it has been shown that green tea polyphenols, when given to TRAMP, a transgenic mouse model that mimics progressive forms of human prostate cancer, exert remarkable preventive effects against prostate cancer development. Chemoprevention of prostate cancer by tea polyphenols appears to occur through the modulation of various molecular targets. This article attempts to address the issue of the possible use of tea, especially green tea, for the chemoprevention of prostate cancer.

Androgens↗
PubMed1994

Antioxidative effects of black tea theaflavins and thearubigin on lipid peroxidation of rat liver homogenates induced by tert-butyl hydroperoxide.

The antioxidative activity of theaflavins (TFs) and thearubigin (TR) purified from the infusion of black tea leaves was examined using the tert-butyl hydroperoxide-induced lipid peroxidation of rat liver homogenates. The concentrations which produced 50% inhibition of lipid peroxidation (IC50) by theaflavin (TF), theaflavin monogallate-A (TFM-A), and TR were 4.88 x 10(-4), 4.09 x 10(-4), and 4.95 x 10(-4%) (w/v), respectively. The anti-oxidative activity of these compounds was higher than that of glutathione, L(+)-ascorbic acid, dl-alpha-tocopherol, butylated hydroxytoluene, butyl hydroxyanisole, etc., but was lower than the activity of (-)-epicatechin gallate, (-)-epigallocatechin, and (-)-epigallocatechin gallate. As to the IC50 in molarity, the antioxidative activity of TFM-A was the second highest among all the samples used in this study. The antioxidative activity of lyophilized tea infusions was compared. The activity of black tea was about as potent as that of green tea. These results suggest that black tea infusion containing TFs and TR could inhibit lipid peroxidation in biological conditions in the same way as green tea infusion containing epicatechins.

Animals↗
PubMed2003

Inhibitory effect of oolong tea on the oxidative state of low density lipoprotein (LDL).

In the present study, we investigated the anti-oxidant activity of oolong tea in an oxidation model using human low-density lipoprotein (LDL). Oolong tea suppressed the oxidation of LDL induced by 2-2'-azobis 4-methoxy-2,4-dimethyvaleronitrile (V70) in a dose-dependent manner, that is, it prolonged the lag time to 114.3%, 138% and 199.9% as compared with the control group at 0.5 microg/ml, 1.0 microg/ml, and 2.5 microg/ml, respectively. We also determined the scavenging effect of oolong tea on active oxygen radicals using the electron spin resonance (ESR) technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trapping agent. The intensity of the ESR signals for the DMPO-OOH adduct formed by the hypoxanthine/xanthine oxidase reaction system with DMPO decreased in the presence of oolong tea. The IC(50) of oolong tea was 19.9 microg/ml. These findings suggested that oolong tea has beneficial effects on health related to its anti-oxidative action.

Antioxidants↗
PubMed2004

Effects of oolong tea on plasma antioxidative capacity in mice loaded with restraint stress assessed using the oxygen radical absorbance capacity (ORAC) assay.

In the present study, we investigated the antioxidative effect of oolong tea in vitro and in vivo using the oxygen radical absorbance capacity (ORAC) assay. An oolong tea extract, catechin and related compounds suppressed the oxidation of fluorescence induced by AAPH in a dose-dependent manner, that is, they prolonged the antioxidant time in vitro. Oral administration of the oolong tea extract to mice treated with restraint stress increased ORAC activity in plasma as compared with a stress control group. The extract also increased plasma vitamin C levels, and there was a good relationship between ORAC activity and the vitamin C level in plasma. The elevation of plasma ORAC and vitamin C level may have been related to the stress-relieving effect of oolong tea. These effects are probably due to the antioxidative properties of the tea. Thus, these findings suggested that oolong tea has beneficial effects on health related to its antioxidative action.

Animals↗
PubMed2006

Anti-ulcer effect of tea catechin in rats.

Oral administration of tea catechin dose-dependently prevented absolute ethanol-induced (50, 100, 200 mg/kg) or restraint plus water immersion stress-induced acute gastric mucosal injury (300, 400 mg/kg) in rats. When the effect of test compound was evaluated on the 15th day after acetic acid injection to rats, repeated oral administration of tea catechin (25, 50, 100 mg/kg twice daily) dose-dependently accelerated the healing of acetic acid-induced chronic gastric ulcers. Tea catechin (10(-5)-10(-1) g/100 ml) concentration-dependently scavenged superoxide anions in vitro. Tea catechin (100, 200 mg/kg orally) markedly inhibited the increase in thiobarbituric acid-reactive substances in the injured mucosa of rats treated with 50% ethanol. Tea catechin (50, 100 mg/kg twice orally, daily) markedly inhibited the increase in content of thiobarbituric acid-reactive substances in the ulcerated region of acetic acid-induced gastric ulcers on the 7th and 15th days. In addition, at 50, 100 and 200 mg/kg orally, it dose-dependently prevented the decrease in gastric mucosal hexosamine content induced by absolute ethanol, although it failed to inhibit the basal gastric acid secretion. These results suggest that tea catechin may primarily protect gastric mucosa from acute gastric mucosal injury and promote the healing of chronic gastric ulcers by its antioxidant activity and gastric mucus-increasing actions.

Acetic Acid↗
PubMed1996

[Antimicrobial and anti-inflammatory actions of tea-leaf saponin].

Antimicrobial and anti-inflammatory actions of tea-leaf saponin, which was a mixture of saponin separated from leaves of Camellia sinensis var. sinensis, were investigated. Tea-leaf saponin showed relatively high antimicrobial activity against pathogenic dermal fungi and its MIC value for Microsporum audouinii was 10 microgam/ml. On the other hand, tea-leaf saponin inhibited rat paw edema induced by carrageenin in a dose dependent manner. Activation of hyaluronidase, one of the enzymes involved in inflammatory reactions, was inhibited by tea-leaf saponin. It was also found that tea-leaf saponin antagonized the action of leukotrien D4, one of the chemical mediators of inflammatory reactions. Any symptom of toxic reaction was not observed when tea-leaf saponin was administered orally to mice at a dose of 2000 mg/kg.

Animals↗
PubMed1996

[Effect of tea-leaf saponin on blood pressure of spontaneously hypertensive rats].

The antihypertensive effect of tea-leaf saponin (the saponin mixture isolated from leaves of Camellia sinensis var. sinensis) was examined in spontaneously hypertensive rats (SHR). Tea-leaf saponin reduced a time-dependent increase in blood pressure dose-dependently when it was administered orally to young SHR (7 weeks old) for 5 d. Oral administration of tea-leaf saponin to elder SHR (15 weeks old) for 5 d decreased the mean blood pressure by 29.2 mmHg at the dose of 100mg/kg compared to the control group. Single administration of tea-leaf saponin at 50mg/kg, p.o. showed a long-lasting hypotensive effect and this effect was as potent as that of enalapril maleate at the dose of 3 mg/kg, p.o. Tea-leaf saponin inhibited angiotensin I-induced contraction of the isolated guinea pig ileum in a dose dependent manner but little depressed angiotensin II-induced contraction. On the other hand, in in vitro experiment using a synthetic peptide as a substrate, tea-leaf saponin showed almost no inhibitory activity against the angiotensin I converting enzyme (ACE) (IC50 > 10 mg/ml).

Angiotensin I↗
PubMed1998

Scavenging effect of various tea extracts on superoxide derived from the metabolism of mutagens.

We determine the superoxide formed in the self-degradation of mutagens activated by cytochrome enzymes and evaluated the scavenging effect of various tea extracts. Benzo[a]pyrene (B[a]P) and 2-amino-6-methyldipyrido(1,2-a:3',2'-d)imidazole (Glu-P-1) each produced a large amount of superoxide after activation by cytochrome enzymes. However, 2-amino-3-methyl-imidazo(4,5-f)quinoline (IQ), 3-amino-1,4-dimethyl-5H-pyridol(4,3-b)indole (Trp-P-1) and alfatoxin B1 (AFB1) failed to generate a significant amount of superoxide. The addition of a tea extract to the reaction system marked inhibited the derivation of superoxide from Glu-P-1. However, the tea extracts showed weaker inhibition of the B[a]P-mediated formation of superoxide. Among the four teas tested, the oolong tea extract tended to exhibit the strongest inhibitory effect. Our results suggest that the chemopreventive efficacy of a tea extract is partly associated with its antioxidative activity.

Animals↗
PubMed2002

Effects of oolong tea on metabolism of plasma fat in mice under restraint stress.

We investigated the effects of oolong tea on the basic metabolism of plasma lipids in mice under restraint stress. When a lipid emulsion (Intralipid 20%; a lipid emulsion containing 20% soybean oil) was injected intravenously into mice, the restraint stress prolonged the half-life (T 1/2) of elimination for plasma triglyceride (TG) from 28.7 to 55.5 min. The elimination rate per minute was 48.2% in stressed mice with the rate in starved control mice as 100%. Therefore, TG metabolism was disrupted by the stress, and the use of TG as an energy source decreased. We found that the metabolism of lipids significantly response to the restrained stress in the present study. Plasma TG was 515.9 +/- 29.9mg/dl 35min after Intralipid administration in control stressed mice, 478.7 +/- 26.7 mg/dl in the stressed group given caffeine 100 mg/kg of body weight, and 418.3 +/- 18.4 mg/dl in the stressed group given 1,000 mg/kg oolong tea, an improvement by 7.2% and 18.9%, respectively, with the value for the untreated control group. The intake of oolong tea alleviated the stress-induced decrease in the rate of blood lipid metabolism; this effect may have arisen from some non-specific stress-relieving property of the tea or from acceleration of lipid metabolism by properties of polyphenols, etc. in tea. Oolong tea had anti-stress effects on plasma TG metabolism, and the effects did not depend on caffeine.

Animals↗
PubMed1999

Photoprotective effect of black tea extracts against UVB-induced phototoxicity in skin.

In previous studies, we showed that green tea and black tea extracts and their major polyphenolic constituents protect against UVB light-induced carcinogenesis in murine skin. All of these studies required chronic administration of tea extracts or specific constituents either topically or orally. However, it is not known whether acute or subchronic administration of black tea extracts or constituents can ameliorate UVB-induced early effects in skin. In the present study, cultured keratinocytes and mouse and human skin were employed to assess the effect of both oral and topical administration of standardized black tea extract (SBTE) and its two major polyphenolic subfractions namely BTF1 and BTF2 against UVB-induced photodamage. In SKH-1 hairless mice, topical application of SBTE (0.2 mg/cm2) prior to UVB exposure (180 mJ/cm2) resulted in 40% reduced incidence and 64% reduced severity of erythema and 50% reduction in skinfold thickness by day 6 when compared to nontreated UVB-exposed animals. The SBTE was also effective in protecting against UVB-induced erythema in human volunteers. Administration of SBTE 5 min after UVB irradiation was similarly effective in reducing UVB-induced inflammation in both murine and human skin. The major polyphenolic subfractions, BTF1 and BTF2, were also effective in protecting in mouse skin. The SBTE subfractions inhibited UVB-induced tyrosine phosphorylation of epidermal growth factor receptor (EGFR). The UVB irradiation of human epidermoid carcinoma cells resulted in 3.3-fold induction of tyrosine phosphorylation of EGFR. Pretreatment with BTF1 and BTF2 reduced tyrosine phosphorylation of EGFR by 53% and 31%, respectively. The UVB-mediated enhanced expression of the early response genes, c-fos and c-jun in human epidermal keratinocytes was reduced in a dose-dependent manner by SBTE. Topical application of SBTE was also effective in reducing accumulation of c-fos and p53 proteins by 82% and 78%, respectively, in UVB-exposed mouse skin. These data provide evidence that constituents of black tea can abrogate UVB-induced erythema and associated early events in murine and human skin.

Administration, Oral↗
PubMed2006

Metabolism of green tea catechins: an overview.

Green tea is one of the most popular beverages worldwide. Its major components include (-)-epicatechin ((-)-EC), (-)-epicatechin-3-gallate (ECG) (-)-epigallocatechin (EGC) and (-)-epigallocatechin-3-gallate (EGCG). It has demonstrated strong antioxidative, anti-inflammatory and anti-cancerous properties and attracted a great deal of interest over last several years. However, there is some discrepancy between the results from human pidemiological studies and cultured cell and animal models. Two reasons for its limited in vivo activities have been considered: metabolism and bioavailability. Recent studies have demonstrated that green tea catechins undergo methylation, glucuronidation and sulfation in in vitro systems and in animals and in humans. It has been also found that efflux transporters Pgp, MRP1 and MRP2 play roles in the absorption and excretion of green tea catechins. Several processes including intestinal metabolism, microbial metabolism, hepatic metabolism and chemical degradation have been found to be involved in the fate of green tea, and to be responsible for its low availability in animals, and most likely also in humans. Pharmacokinetics, absorption, distribution, drug metabolism and excretion properties of green tea provide a better understanding for its in vivo activities. In this article, drug metabolism and microbial metabolism of green tea catechins in in vitro systems and in animals and in humans will be reviewed. It also covers the factors affecting their biotransformation and bioavailability: drug-drug inhibitory and inductive interactions of phase I and phase II enzymes, inhibition of non-drug-metabolizing enzymes, transporters, chemical instability, epimerization and interindividual variability.

Animals↗
PubMed2003

Skin photoprotection by green tea: antioxidant and immunomodulatory effects.

Because of a characteristic aroma and health benefits, green tea is consumed worldwide as a popular beverage. The epicatechin derivatives, commonly called polyphenols, present in green tea possess antioxidant, anti-inflammatory and anti-carcinogenic properties. The major and most highly chemopreventive constituent in green tea responsible for the biochemical or pharmacological effects is (-)-epigallocatechin-3-gallate (EGCG). Epidemiological, clinical and biological studies have implicated that solar ultraviolet (UV) light is a complete carcinogen and repeated exposure can lead to the development of various skin disorders including melanoma and nonmelanoma skin cancers. We and others have shown that topical treatment or oral consumption of green tea polyphenols (GTP) inhibit chemical carcinogen- or UV radiation-induced skin carcinogenesis in different laboratory animal models. Topical treatment of GTP and EGCG or oral consumption of GTP resulted in prevention of UVB-induced inflammatory responses, immunosuppression and oxidative stress, which are the biomarkers of several skin disease states. Topical application of GTP and EGCG prior to exposure of UVB protects against UVB-induced local as well as systemic immune suppression in laboratory animals, which was associated with the inhibition of UVB-induced infiltration of inflammatory leukocytes. Prevention of UVB-induced suppression of immune responses by EGCG was also associated with the reduction in immunosuppressive cytokine interleukin (IL)-10 production at UV irradiated skin and draining lymph nodes, whereas IL-12 production was significantly enhanced in draining lymph nodes. Antioxidant and anti-inflammatory effects of green tea were also observed in human skin. Treatment of EGCG to human skin resulted in the inhibition of UVB-induced erythema, oxidative stress and infiltration of inflammatory leukocytes. We also showed that treatment of GTP to human skin prevents UVB-induced cyclobutane pyrimidine dimers formation, which are considered to be mediators of UVB-induced immune suppression and skin cancer induction. The in vitro and in vivo animal and human studies suggest that green tea polyphenols are photoprotective in nature, and can be used as pharmacological agents for the prevention of solar UVB light-induced skin disorders including photoaging, melanoma and nonmelanoma skin cancers after more clinical trials in humans.

Adjuvants, Immunologic↗