A review of latest research findings on the health promotion properties of tea

Nutritional risk factors for the development of hypertension in diabetic patients

The aim of this cross-sectional study was to determine the significant limitations, sensitivity, specificity, partial correlations, and odds ratios of nutrient intake in patients with and without hypertension with Type 2 diabetes mellitus. Diabetic patients (n=220) with clinical diagnosis of hypertension and diabetic patients (n=230) without hypertension were included in this study. The questionnaire form included a list of 65 food items formed from five main food groups (grain, meat and alternatives, dairy products, vegetables-fruits and fat) and 25 dietary habits. When both groups were compared and analyzed by logistic regression, black tea consumption (OR=0.823, P<.001), vegetables-fruits scores (OR=0.853, P<.001), triglycerides (OR=0.726, P<.05), waist-to-hip ratio (WHR) (OR=0.777, P<.01) and high-density lipoprotein cholesterol (HDL-C) (OR=0.526, P<.001) made significant differences. In ROC curves, the area under the curve of black tea (0.921), vegetables-fruits (0.906), triglycerides (0.889), WHR (0.881) and HDL-C (0.820) provided high accuracy to distinguish between patients with and without hypertension (P<.001). In diabetic patients without hypertension, significant partial correlations were observed between blood pressure and dairy products (systolic: r=)0.14; diastolic: r=)0.14, P<.05), vegetables-fruits groups (systolic: r=)0.18; diastolic: r=)0.17, P<.01) and black tea intake (systolic: r=)0.23; diastolic: r=)0.22, P<.001). It has been found that higher intake of black tea and vegetables-fruits consumption in diabetic patients protect against developing hypertension.

Studies on the protective effect of green tea against cisplatin induced nephrotoxicity

Cisplatin (CP) an anticancer drug is known to induce nephrotoxicity, which limits its long-term clinical use. Green tea (GT), consumed since ancient times is known for its numerous health benefits. It has been shown to improve kidney functions in animal models of acute renal failure. The present study was undertaken to see whether GT can prevent CP-induced nephrotoxic and other deleterious effects. A nephrotoxic dose of CP was co-administered to control and GT-fed male Wistar rats every fifth day for 25 days. The effect of GT was determined on CP-induced alterations in various serum parameters and on enzymes of carbohydrate metabolism, brush border membrane, and antioxidant defense system in renal cortex and medulla. CP nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. CP increased the activities of lactate dehydrogenase and acid phosphatase whereas, the activities of malate dehydrogenase, glucose-6-phosphatase, superoxide dismutase, catalase, and (32)Pi transport significantly decreased. GT consumption increased the activities of the enzymes of carbohydrate metabolism, brush border membrane, oxidative stress, and (32)Pi transport. GT ameliorated CP-induced nephrotoxic and other deleterious effects due to its intrinsic biochemical/antioxidant properties.

In vitro antioxidant and free radical scavenging activities of Garcinia kola seeds

Garcinia kola Heckel--a tropical plant which grows in moist forest, has found wide applications in traditional medicine especially in the West and Central African sub-region. The seeds have been demonstrated to possess numerous bioactivities but research is highly limited on the link between its fractions and the bioactivities. In this work, the methanolic extract of Garcinia kola seeds was subjected to silica gel column chromatography into five fractions ME1-ME5 and the free radical scavenging activities and antioxidant potentials were determined for each fraction using various in vitro models. The ME4 fraction possessed the greatest activities. It was also demonstrated that the ME4 fraction strongly inhibited nitric oxide production in lipopolysaccharide activated macrophage U937 cells. Chromatographic fractionation and spectroscopic analysis of the ME4 fraction revealed the presence of four compounds namely garcinia biflavonoids GB1 and GB2, garcinal and garcinoic acid. These findings show that these four compounds are partly responsible for the great antioxidant potential of Garcinia kola seeds. This gives further evidence to the nutraceutical and pharmaceutical potential of Garcinia kola.

Effect of daily fruit ingestion on angiotensin converting enzyme activity, blood pressure, and oxidative stress in chronic smokers

OBJECTIVE

This study examined whether, daily fruit (blueberries) consumption (250 g) for three weeks or acute fruit ingestion (250 g) would attenuate angiotensin converting enzyme (ACE) activity and reduce oxidative stress in chronic cigarette smokers.

METHODS

Twenty subjects were recruited and randomized into fruit or control groups. Blood samples and blood pressure were obtained at baseline and then pre and one hour post when subjects returned to the lab three weeks later. To examine acute effects, the fruit group immediately ingested 250 g of blueberries after returning and at least one hour prior to the post blood draw. Plasma samples were analyzed for ACE activity, F(2)- isoprostanes and lipid hydroperoxides (LH) as measures of oxidative stress, and ferric reducing ability of plasma (FRAP) as a measure of antioxidant potential. A 2 (treatment) x 3 (time) repeated measures ANOVA was used for statistical analysis. If interaction was significant, then Student's t-tests were used to further examine this relationship. For these comparisons, a Bonferroni adjustment was made with statistical significance set at P < 0.025.

RESULTS

The pattern of change between treatments was not significant for any variable except LH (P < 0.001).

CONCLUSION

This study indicates that LH are significantly reduced by daily fruit consumption, but not affected by acute ingestion. This finding could be one way in which fruit consumption contributes to prevention of cardiovascular disease.

The LAP1 MYB transcription factor orchestrates anthocyanidin biosynthesis and glycosylation in Medicago

MYB transcription factors help to control anthocyanin biosynthesis in plants, and ectopic expression of the Arabidopsis Production of Anthocyanin Pigment 1 (PAP1) transcription factor activates the anthocyanin pathway in tobacco, suggesting the general utility of such factors for metabolic engineering of anthocyanins and anthocyanin-derived compounds such as proanthocyanidins (condensed tannins). However, PAP1 does not activate anthocyanin biosynthesis in the model legume Medicago truncatula or in alfalfa (Medicago sativa). A related Legume Anthocyanin Production 1 (LAP1) gene was identified from the genome of M. truncatula. When constitutively expressed in transgenic alfalfa, M. truncatula or white clover, LAP1 induced massive accumulation of anthocyanin pigments comprising multiple glycosidic conjugates of cyanidin. Oligomeric/polymeric compounds with some diagnostic characteristics of proanthocyanidins also accumulated in LAP1-expressing plants, but these compounds were not composed of (epi)catechin units. Over 260 and 70 genes were up-regulated in leaves of alfalfa or M. truncatula, respectively, in response to constitutive expression of LAP1, many of which are involved in anthocyanin biosynthesis. In particular, the glucosyltransferase UGT78G1, previously identified as showing preference for isoflavonoid substrates in vitro, was strongly up-regulated by LAP1, and appears to function as an anthocyanin glycosyltransferase in vivo. Over-expression of UGT78G1 in transgenic alfalfa resulted in increased anthocyanin accumulation when plants were exposed to abiotic stress.

The green tea polyphenol (-)-epigallocatechin-3-gallate inhibits leukocyte activation by bacterial formylpeptide through the receptor FPR

Although green tea polyphenol catechin is considered as a potential anti-inflammatory agent, its effect on bacterial component-induced inflammation has been poorly investigated. We examined the capacity of epigallocatechin gallate (EGCG) to regulate leukocyte responses to bacterial chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (fMLF), which is recognized by a human G protein-coupled receptor FPR on phagocytic leukocytes. Pretreatment of human monocytic cells or FPR-transfected rat basophilic leukemia cells (ETFR cells) with EGCG significantly inhibited fMLF-induced chemotaxis. Intraperitoneal administration of EGCG in mice suppressed fMLF-induced leukocyte infiltration into the air pouch created in the skin. Mechanistic studies revealed that EGCG dose-dependently suppressed fMLF-induced calcium flux in monocytic cells and ETFR cells. fMLF-induced ETFR cell migration was significantly inhibited by a specific MEK1/2 inhibitor, PD98059, which was associated with reduction in fMLF-induced ERK1/2 phosphorylation. These results suggest that EGCG inhibits FPR-mediated leukocyte activation thus is a promising anti-inflammatory compound.

Hepatotoxicity from green tea: a review of the literature and two unpublished cases

PURPOSE

To review the current literature on suspected green tea-related hepatic reactions and to describe two new cases reported within the framework of the Italian surveillance system of natural health products.

RESULTS

A literature search of publication between 1999 and October 2008 retrieved 34 cases of hepatitis. Histological examination of the liver revealed inflammatory reactions, cholestasis, occasional steatosis, and necrosis. A positive dechallenge was reported in 29 cases. There was one reported death. A positive rechallenge occurred in seven cases (20%). In the two new cases, the causality assessment was judged as "possible" according to the RUCAM score.

CONCLUSIONS

Our analysis of the published case reports suggests a causal association between green tea and liver damage. The hepatotoxicity is probably due to (-)-epigallocatechin gallate or its metabolites which, under particular conditions related to the patient's metabolism, can induce oxidative stress in the liver. In a few cases, toxicity related to concomitant medications could also be involved.

Drinking green tea modestly reduces breast cancer risk

Green tea is a commonly consumed beverage in China. Epidemiological and animal data suggest tea and tea polyphenols may be preventive against various cancers, including breast cancer. Catechol-O-methyltransferase (COMT) catalyzes catechol estrogens and tea polyphenols. The COMT rs4680 AA genotype leads to lower COMT activity, which may affect the relationship between green tea consumption and breast cancer risk. We evaluated whether regular green tea consumption was associated with breast cancer risk among 3454 incident cases and 3474 controls aged 20-74 y in a population-based case-control study conducted in Shanghai, China during 1996-2005. All participants were interviewed in person about green tea consumption habits, including age of initiation, duration of use, brew strength, and quantity of tea. Odds ratios (OR) and 95% CI were calculated for green tea consumption measures and adjusted for age and other confounding factors. Compared with nondrinkers, regular drinking of green tea was associated with a slightly decreased risk for breast cancer (OR, 0.88; 95% CI, 0.79-0.98). Among premenopausal women, reduced risk was observed for years of green tea drinking (P-trend = 0.02) and a dose-response relationship with the amount of tea consumed per month was also observed (P-trend = 0.046). COMT rs4680 genotypes did not have a modifying effect on the association of green tea intake with breast cancer risk. Drinking green tea may be weakly associated with a decreased risk of breast cancer.

Preservation of kombucha tea-effect of temperature on tea components and free radical scavenging properties

Kombucha tea is sugared black tea fermented with a consortium of acetic acid bacteria and yeasts (tea fungus) for 14 days. The tea tastes slightly sweet and acidic. The formation of tea fungal biofilms during storage is a big problem when kombucha tea is being stored and commercialized. Various thermal treatments have been tried for long-term storage of kombucha tea. The present study revealed the influence of heat on the biochemical constituents and the free radical scavenging properties of kombucha tea. Heat treatment at 60, 65, and 68 degrees C for 1 min controlled biofilm formation in kombucha tea without changing its clarity, taste, and flavor. However, tea polyphenols and black tea quality parameters showed varying stability during the storage period. A decrease in free radical scavenging properties was also found during the storage period. Because the biological activities of kombucha tea depended on the biochemical constituents, it was concluded that heat treatment was not a suitable method for kombucha tea preservation.

Total polyphenol content and antioxidant capacity of commercially available tea (Camellia sinensis) in Argentina

Tea, Camellia sinensis (L.) O. Kuntze (Theaceae) is cultivated in Argentina in the northeastern region (provinces of Misiones and Corrientes), between 26 degrees and 28 degrees south latitude, the southernmost area of the world where tea is cultivated. The objective of this work was to determine the total polyphenol content and the in vitro antioxidant capacity of green and black tea cultivated and industrialized in Argentina. Twelve samples of eight brands were analyzed. The total polyphenol content was determined according to the International Organization for Standardization method (ISO) 14502-1 for the determination of substances characteristic of green and black tea. The antioxidant capacity was determined by the ferric thiocyanate method (FTC) and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging assay. Green tea showed a higher polyphenol content than black tea. The total polyphenol concentration in green tea was found to vary from 21.02 +/- 1.54 to 14.32 +/- 0.45% of gallic acid equivalents (GAE), whereas in black tea, the polyphenol content ranged from 17.62 +/- 0.42 to 8.42 +/- 0.55% of GAE (P < 0.05). A similar profile was observed for the antioxidant capacity determined by both methods. The antioxidant activities were well correlated with the total polyphenol content (r (2) = 0.9935 for the ferric thiocyanate method and r (2) = 0.9141 for the 1,1-diphenyl-2-picrylhydrazyl free-radical scavenging assay). This is the first systematic screening for the quantification of polyphenols and antioxidant activity in tea commercialized in Argentine markets. The results obtained herein allow one to conclude that Argentine tea is of very good quality when compared to teas from other sources.

New phenolic components and chromatographic profiles of green and fermented teas

A standardized profiling method based on liquid chromatography with diode array and electrospray ionization mass spectrometric detection (LC-DAD-ESI/MS) was applied to establish the phenolic profiles of 41 green teas and 25 fermented teas. More than 96 phenolic compounds were identified that allowed the teas to be organized into five groups. Epigallocatechin gallate (EGCG) was the major phenolic component of green tea made from mature leaves (group 2), while green tea made from the younger buds and leaves (group 1) contained lower flavonoid concentrations. Partially fermented teas (group 3) contained one-half the EGCG content of the green tea. Fully fermented black teas (group 4) had a trace of EGCG, but contained theaflavins. Highly overfermented black tea (group 5) contained only trace amounts of flavonol glycosides and theaflavins. Over 30 phenolics are new for tea, and this is the first phenolic profile to simultaneously detect C- and O-glycosylated flavonoids, catechins, proanthocyanidins, phenolic acid derivatives, and purine alkaloids.

Chromatographic Examinations of Tea's Protection Against Lipid Oxidative Modifications

Ethanol metabolism is accompanied by generation of free radicals that damage cell components, especially lipids. The present study was designed to investigate the efficacy of the preventive effect of black tea on the lipid oxidative modifications in different tissues (plasma, liver, brain, kidney, stomach, lung, intestine, and spleen) of 12-month-old rats chronically intoxicated with ethanol. Ethanol intoxication caused changes in the level/activity of antioxidants that led to the significant increase in the level of lipid oxidative modification products. Oxidative modifications were estimated by measuring lipid hydroperoxides, malondialdehyde, and 4-hydroxynonenal by high-performance liquid chromatography (HPLC) and by spectrophotometric determination of conjugated dienes. These lipid-modification marker levels were increased in almost all examined tissues (3%–71%) after ethanol intoxication. Described changes were in accordance with the liver level of the most often used marker of arachidonic acid oxidation, isoprostane (8-isoPGF_2α), determined by the LC/MS system. Administration of black tea to ethanol-intoxicated rats remarkably prevents the significant increase (by about 15%–42%) in concentrations of all measured parameters regarding all examined tissues, but especially the plasma, liver, brain, stomach, and spleen. The preventive effect of black tea in the other organs (kidney, lung, intestine) caused a decrease in examined markers in a smaller degree (by about 7%–28%). To determine in the liver the major constituents of black tea mainly responsible for antioxidative action such as catechins and theaflavins, which were absorbed in organism, the present study indicates their protective effect against ethanol-induced oxidative modifications of lipids.

Assessment of the content of phenolics and antioxidant actions of the Rubiaceae, Ebenaceae, Celastraceae, Erythroxylaceae and Sterculaceae families of Mauritian endemic plants

There is continued interest in the assessment of the bioefficacy of the active principles in extracts from a variety of traditional medicine and food plants in order to determine their impact on the management of a variety of clinical conditions and maintenance of health. The polyphenolic composition and antioxidant potential of Mauritian endemic plants of the Rubiaceae, Ebenaceae, Celastraceae, Erythroxylaceae and Sterculaceae family were determined. The phenolics level of the plant extracts varied from 1 to 75 mg/g FW, the maximum level measured in Diospyros neraudii (Ebenaceae). Coffea macrocarpa showed the highest flavonoids content with 18+/-0.7 mg/g FW. The antioxidant capacity based on the TEAC and FRAP values were strongly related to total phenolics and proanthocyanidins content, while a weaker correlation was observed with (-) gallic acid. Erythroxylum sideroxyloides showed the highest protective effect in the lipid peroxidation systems with IC(50) of 0.0435+/-0.001 mg FW/ml in the Fe(3+)/ascorbate system and 0.05+/-0.002 mg FW/ml in the AAPH system. Cassine orientalis, E. sideroxyloides, Diospyros mellanida and Chassalia coriancea var. johnstonii were weakly prooxidant only at higher concentration greater of 10 g FW/L indicating potential safety. Mauritian endemic plants, particularly the genus Diospyros, are good sources of phenolic antioxidants and potential candidates for the development of prophylactic agents.

Effect of green tea extract on advanced glycation and cross-linking of tail tendon collagen in streptozotocin induced diabetic rats

Diabetes leads to modification of collagen such as advanced glycation and cross-linking which play an important role in the pathogenesis of diabetes mellitus. We have investigated the effect of green tea on modification of collagen in streptozotocin (60 mg/kg body weight) induced diabetic rats. To investigate the therapeutic effect of green tea, treatment was begun six weeks after the onset of diabetes and green tea extract (300 mg/kg body weight) was given orally for 4 weeks. The collagen content, extent of advanced glycation, advanced glycation end products (AGE) and cross-linking of tail tendon collagen were investigated. Green tea reduced the tail tendon collagen content which increased in diabetic rats. Accelerated advanced glycation and AGE in diabetic animals, as detected by Ehrlich's-positive material and collagen linked fluorescence respectively were reduced significantly by green tea. The solubility of tail tendon collagen decreased significantly in diabetic rats indicating a remarkable increase in the cross-linking, whereas green tea increases the solubility of collagen in diabetic rats. The present study reveals that green tea is effective in reducing the modification of tail tendon collagen in diabetic rats. Thus green tea may have a therapeutic effect in the treatment of glycation induced complications of diabetes.

Effect of blueberry feeding on plasma lipids in pigs

Two feeding trials were conducted with pigs to determine the effects of blueberry supplementation on plasma lipid levels and other indices of cardiovascular benefit. In the first trial, where basal diets contained a high level of plant-based components (70 % soya, oats and barley), supplementation with 1, 2 and 4 % blueberries resulted in a decrease in total, LDL- and HDL-cholesterol. The greatest reduction was observed in the 2 % blueberry-fed pigs, where total, LDL- and HDL-cholesterol were reduced 11.7, 15.1 and 8.3 %, respectively. In the second trial where basal diets contained only 20 % (w/w) of soya, oats and barley, the lipid-modulating effect of blueberries was attenuated, so that supplementation with 1.5 % blueberries reduced total cholesterol by 8 %, which occurred only in pigs whose diets had been supplemented with cholesterol (0.08 %), NaCl (0.11 %) and fructose (9 %). In the first feeding trial, blueberry supplementation had no effect on blood platelet activity. Blueberry supplementation also had no effect on the susceptibility of leucocyte DNA to oxidation in the first trial and no effect on the susceptibility of LDL to oxidation in the second trial. Results of these two feeding trials are discussed in relation to the effects of basal diet composition on lipid-modulating effects of blueberries.

Protective effects of green tea polyphenols against subacute hepatotoxicity induced by microcystin-LR in mice

Green tea polyphenols (GTP) have been shown to possess anti-oxidative, anti-mutagenic and anti-carcinogenic activities. The present study aimed to evaluate the chemopreventive efficacy of GTP against subacute hepatotoxicity induced by microcystin-LR (MC-LR) in mice and also elucidates the underlying mechanisms. In this study, healthy Kunming male mice (24-26gbw) were randomly assigned to five groups. Group I was fed on normal diet and water ad libitum as control. Group II was maintained on normal diet and received MC-LR intraperitoneal injection (10μg/kg/day) from day 6 till sacrifice. Mice in groups III, IV and V were daily pre-treated with GTP through intragastric administration at doses of 50, 100 and 200mg/kg/day from day 0 prior to MC-LR intoxication, consecutively 18 days. The results showed MC-LR alone led to oxidative stress and to damage antioxidant defense system, as evidenced by elevation of serum and liver lipid peroxidation. Additionally, hepatocellular apoptosis and injury were significantly observed. GTP pre-treatment caused a significant elevation in serum antioxidant enzymes GSH and SOD activities as well as a decrease in hepatic lipid peroxidation MDA level and serum ALT, AST, ALP activities. GTP pre-treatment obviously inhibited hepatocellular apoptosis and up-regulated Bcl-2 protein expression. The damages in liver were less severe in GTP pre-treated mice in correlation with the biochemical parameters. In summary, this study confirmed that repeated exposure to MC-LR could induce hepatotoxicity. Our study demonstrated that GTP can reduce MC-LR-induced oxidant stress and prevent biochemical parameters and pathological changes caused by MC-LR in a dose-dependent manner. The results indicated that tea polyphenols have a potential to be developed as a preventive agent against MC-LR-induced toxicity and the mechanism involved in the protection could be due to their antioxidant activities.

Tea beverage in chemoprevention and chemotherapy of prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed malignancy and the second leading cause of cancer-related deaths in American males with similar trends in many western countries. The existing treatment approaches and surgical intervention have not been able to effectively cope with this dreaded disease. For these reasons, it is necessary to intensify our efforts for a better understanding of the disease process and for the development of novel approaches for its prevention and treatment. Based on considerable evidence from in vivo and in vitro data and epidemiological studies, in recent years the beverage tea has gained considerable attention for reducing the risk of several cancers. Much of the cancer preventive effects of tea, especially green tea appear to be mediated by the polyphenols present therein. Geographical evidence suggests that the incidence and occurrence of PCa is lower in populations that consume tea regularly. This evidence suggests that tea polyphenols could be extrapolated to optimize their chemopreventive properties against PCa. PCa represents an excellent candidate disease for chemoprevention because it is typically diagnosed in men over 50 years of age and therefore, even a modest delay in neoplastic development achieved through pharmacological or nutritional intervention could result in a substantial reduction in the incidence of clinically detectable disease. In this review we address the issue of possible use of tea, especially green tea, for the prevention as well as treatment of PCa.

Effect of supplementation of green tea polyphenols on the developmental competence of bovine oocytes in vitro

The objective of the present study was to examine the effect of green tea polyphenols (GTPs) supplementation during in vitro maturation, in vitro fertilization, and in vitro culture on the developmental competence of bovine oocytes. Cumulus-oocyte complexes aspirated from the ovaries were matured in vitro (38.5 degrees C for 24 h) and fertilized (38.5 degrees C for 15-18 h) and embryos were cultured (38.5 degrees C for 192 h) in a defined conditioned medium with or without GTPs supplementation. The GTPs used in the present study contained 99% catechin derivatives, with the major components being 50% (-)-epigallocatechin gallate, 22% (-)-epicatechin gallate, 18% (-)-epigallocatechin, and 10% (-)-epicatechin. Four replicate trials were done for each type of experiment. GTPs supplementation (15 microM) of the maturation medium led to a significant increase in the rate of blastocyst formation (34.0 vs 21.4%, P < 0.05). However, the rate of blastocyst formation was not improved when higher GTPs concentrations (20 or 25 microM) were added to the in vitro maturation medium. During in vitro fertilization, supplementation with higher GTPs concentrations (20 or 25 microM) significantly reduced the rate of blastocyst formation (P < 0.05). Supplementation of the culture medium with 15 microM GTPs improved the rate of blastocyst formation, while higher GTPs concentrations (25 microM) significantly reduced embryo development (P < 0.05). In conclusion, these results demonstrate that supplementation with GTPs at low concentration (15 microM) during in vitro maturation and in vitro culture improved the developmental competence of bovine oocytes.

Improvement in bovine embryo production in vitro by treatment with green tea polyphenols during in vitro maturation of oocytes

The present study examined the effect of green tea polyphenols (GTP) during in vitro maturation (IVM) of bovine oocytes on in vitro fertilization (IVF) parameters, intracellular glutathione (GSH) concentration and subsequent embryo development. Cumulus-oocyte complexes were aspirated from the ovaries derived from slaughterhouse and cultured in modified synthetic oviduct fluid (m-SOF) supplemented with 0-25 microM GTP for 24h. After IVM, cumulus-free oocytes were coincubated with frozen-thawed spermatozoa for 15-18 h. Putative embryos were transferred to m-SOF and cultured for 8 days (Experiment 1). In comparison with the absence of GTP, treatment with GTP at a concentration of 15 microM showed a significant increase in the proportion of pronuclear (PN) formation after sperm penetration (65% versus 80%, P<0.05). No significant differences in the rates of sperm penetration and polyspermic fertilization were found among treatments. The cleavage rate at 48 h of in vitro insemination showed no difference in oocytes matured with or without GTP. However, compared to no addition (23.5%), the presence of 15 and 20 microM GTP during IVM significantly (P<0.05) increased the proportion of blastocysts (38.1% and 36.4%) on day 9 of in vitro insemination. A further increase from 20 to 25 microM GTP reduced (P<0.05) the proportion of blastocysts. In Experiment 2, after IVM, oocytes were fixed to analyze the GSH concentration. Compared to no addition, a higher (P<0.05) level of GSH was found in oocytes matured with 15 microM GTP and compared with 15 microM GTP, GSH was low (P<0.05) at 20 and 25 microM GTP. The results suggest that at certain concentrations of GTP (15 microM) in IVM medium has beneficial effects on subsequent embryo development, and is correlated with intracellular GSH level in bovine oocytes.

Preparation of partially decaffeinated instant green tea

The caffeine level of instant tea extracted from decaffeinated leaf tea with 4.0 mg g-1 caffeine is commonly above 10.0 mg g-1, the maximum limit of caffeine for decaffeinated instant tea. Further removal of caffeine by active carbon (AC) from the green tea extract was investigated. It showed that the removal of caffeine from the tea extract solutions depended on the treatment time and tea extract concentration while the ethanol concentration and pH had little effect on the removal of caffeine. According to the removal of caffeine and the ratio of total catechins to caffeine in the tested samples, the optimum decaffeination conditions were determined to be as follows: tea extract concentration 15-30 g L-1 for common tea extract but higher for partially decaffeinated tea leaf extract; ratio of tea solution to AC, 100 mL:4 g; treatment time, 4 h; and natural tea extract pH. Instant tea powder extracted from partially decaffeinated leaf tea with a caffeine level of 4.03 mg g-1 and further decaffeinated by AC had a caffeine level of 7.81 mg g-1, which was 31% lower than that without AC treatment.

Modulatory effects of black tea polyphenols on oxidant-antioxidant profile and expression of proliferation, apoptosis, and angiogenesis-associated proteins in the rat forestomach carcinogenesis model

BACKGROUND

Chemoprevention by dietary constituents has emerged as a novel approach to control stomach cancer incidence. We therefore evaluated the chemopreventive effects of black tea polyphenols (Polyphenon-B) on oxidant-antioxidant status, cell proliferation, apoptosis, and angiogenesis during N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis.

METHODS

Male Wistar rats were divided into four groups. Rats in group 1 and 2 were given MNNG (150 mg/kg body weight) by intragastric intubation three times at 2 week intervals and followed for 26 weeks. Rats in group 2 received in addition a basal diet containing 0.05% Polyphenon-B. Group 3 animals were given 0.05% Polyphenon-B alone. Group 4 animals served as controls. The status of lipid peroxidation and antioxidants and the expression of the lipid peroxidation marker 4-hydroxy nonenal (4-HNE), proliferating cell nuclear antigen (PCNA), glutathiones-transferase (GST)-pi, Bcl-2, Bax, cytochrome C, caspase 3, cytokeratins, and vascular endothelial growth factor (VEGF) were used as biomarkers.

RESULTS

Intragastric administration of MNNG induced well-differentiated squamous cell carcinomas that showed diminished lipid and protein oxidation and an increase in antioxidant status. This was associated with increased cell proliferation, angiogenesis, and invasive potential coupled with apoptosis evasion as revealed by upregulation of PCNA, GST-pi, Bcl-2, cytokeratins, and VEGF and downregulation of Bax, cytochrome C, and caspase 3 protein expression. Dietary administration of Polyphenon-B effectively suppressed MNNG-induced gastric carcinogenesis, as evidenced by modulation of oxidant-antioxidant status, inhibition of cell proliferation and infiltration, and angiogenesis associated with apoptosis induction.

CONCLUSIONS

The present study provides evidence that Polyphenon-B exerts multifunctional inhibitory effects on MNNG-induced gastric carcinogenesis and suggests that it can be developed as a potential chemopreventive agent.

Epigallocatechin-3-gallate suppresses NF-kappaB activation and phosphorylation of p38 MAPK and JNK in human astrocytoma U373MG cells

Epigallocatechin-3-gallate (EGCG) is the major polyphenol component of green tea and is primarily responsible for the green tea effect. EGCG possesses two triphenolic groups in its structure. These groups are reported to be important with respect to anticarcinogenic and antioxidant effects. However, the anti-inflammatory effect of EGCG on Alzheimer's disease (AD) is still not fully understood. In this study, we investigated the effects of EGCG in attenuating the inflammatory response induced by interleukin (IL)-1beta+beta-amyloid (25-35) fragment (Abeta) in human astrocytoma, U373MG cells. EGCG significantly inhibited the IL-1beta+Abeta (25-35)-induced IL-6, IL-8, vascular endothelial growth factor (VEGF) and prostaglandin (PG)E(2) production at 24 h (P<.01). The maximal inhibition rate of IL-6, IL-8, VEGF and PGE(2) production by EGCG was approximately 54.40%, 56.01%, 69.06% and 47.03%, respectively. EGCG also attenuated the expression of cyclooxygenase-2 and activation of nuclear factor-kappaB induced by IL-1beta+Abeta (25-35). We demonstrated that EGCG suppresses IL-1beta+Abeta (25-35)-induced phosphorylation of the mitogen-activated protein kinase p38 and the c-Jun N-terminal kinase. In addition, EGCG induced the expression of mitogen-activated protein kinase phosphatase-1. These results provide new insight into the pharmacological actions of EGCG and its potential therapeutic application to various neurodegenerative diseases such as AD.

Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and fat oxidation in men

It has been reported that green tea has a thermogenic effect, due to its caffeine content and probably also to the catechin, epigallocatechin-3-gallate (EGCG). The main aim of the present study was to compare the effect of a mixture of green tea and Guarana extracts containing a fixed dose of caffeine and variable doses of EGCG on 24 h energy expenditure and fat oxidation. Fourteen subjects took part to this randomized, placebo-controlled, double-blind, cross-over study. Each subject was tested five times in a metabolic chamber to measure 24 h energy expenditure, substrate oxidation and blood pressure. During each stay, the subjects ingested a capsule of placebo or capsules containing 200 mg caffeine and a variable dose of EGCG (90, 200, 300 or 400 mg) three times daily, 30 min before standardized meals. Twenty-four hour energy expenditure increased significantly by about 750 kJ with all EGCG–caffeine mixtures compared with placebo. No effect of the EGCG–caffeine mixture was observed for lipid oxidation. Systolic and diastolic blood pressure increased by about 7 and 5 mmHg, respectively, with the EGCG–caffeine mixtures compared with placebo. This increase was significant only for 24 h diastolic blood pressure. The main finding of the study was the increase in 24 h energy expenditure with the EGCG–caffeine mixtures. However, this increase was similar with all doses of EGCG in the mixtures.

Effect of liming and seasonal variation on lead concentration of tea plant (Camellia sinensis (L.) O. Kuntze)

Tea is a widely consumed beverage. However, recent studies revealed that there were an increasing number of cases of tea products exceeding the former maximum permissible concentration (MPC) in China for Pb (2 mg kg(-1)). Tea Pb contamination is an issue affecting trade and consumer confidence. Root uptake of Pb could contribute significantly to Pb accumulation in tea leaves due to the strong acidity of many tea garden soils. We conducted pot and field experiments to evaluate the effect of liming on Pb uptake by tea plants on two highly acidic soils (pH3.6). Additions of CaCO(3) significantly increased soil pH by up to 1 unit and decreased soil extractable Pb by up to 32%. Liming resulted in a decrease in the proportion of Pb in the exchangeable and carbonate-bound fractions, with a concurrent increase in the fractions bound to Fe/Mn oxides and residues. Liming significantly decreased Pb concentrations of fine roots, stems and new shoots of tea plants in the pot experiment. In the field experiments, the effect of liming was not significant during the first year following CaCO(3) application, but became significant during the second and third years and Pb concentration in the new shoots was decreased by approximately 20-50%, indicating that liming of acidic tea garden soils is an effective way to reduce Pb contamination of tea. The study also reveals a distinct seasonal variation, with Pb concentration in the new shoots following the order of spring>autumn>summer.

Modulatory effects of black tea polyphenols on rat forestomach carcinogenesis

ABSTRACT The present study was designed to evaluate the chemopreventive effects of black tea polyphenols (Polyphenon-B) on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats. Intragastric administration of MNNG induced well-differentiated squamous cell carcinomas that showed diminished mitochondrial lipid and protein oxidation and an increase in antioxidants. In contrast to tumor tissue, the liver mitochondria of tumor-bearing animals showed elevated lipid and protein oxidation with compromised antioxidant defenses. Dietary administration of Polyphenon-B effectively suppressed MNNG-induced stomach tumors, modulated mitochondrial lipid and protein oxidation, and enhanced antioxidant enzyme activities in the stomach and liver. Our results suggest that Polyphenon-B may exert its chemopreventive effects by modulating mitochondrial cellular redox status in the tumor as well as in the host liver.

Protection from experimental colitis by theaflavin-3,3'-digallate correlates with inhibition of IKK and NF-kappaB activation

BACKGROUND AND PURPOSE

Inflammatory bowel disease (IBD) is associated with activation of nuclear factor kappa B (NF-kappaB) involved in regulating the expression of inducible nitric oxide synthase (iNOS) and proinflammatory cytokine genes. As theaflavin-3,3'-digallate (TFDG), the most potent anti-oxidant polyphenol of black tea, down-regulates NF-kappaB activation, we investigated if TFDG is beneficial in colonic inflammation by suppressing iNOS and proinflammatory cytokines.

EXPERIMENTAL APPROACH

The in vivo efficacy of TFDG was assessed in mice with trinitrobenzene sulfonic acid (TNBS)-induced colitis. Both mRNA and protein levels of proinflammatory cytokines and iNOS were analyzed in colon tissue treated with or without TFDG. NF-kappaB activation was determined by electrophoretic mobility shift assay and levels of NF-kappaB inhibitory protein (IkappaBalpha) were analyzed by Western blotting.

KEY RESULTS

Oral administration of TFDG (5 mg kg(-1) daily i.g.) significantly improved TNBS-induced colitis associated with decreased mRNA and protein levels of TNF-alpha, IL-12, IFN-gamma and iNOS in colonic mucosa. DNA binding and Western blotting revealed increase in NF-kappaB activation and IkappaBalpha depletion in TNBS-treated mice from Day 2 through Day 8 with a maximum at Day 4, which resulted from increased phosphorylation of IkappaBalpha and higher activity of IkappaB kinase (IKK). Pretreatment with TFDG markedly inhibited TNBS-induced increases in nuclear localization of NF-kappaB, cytosolic IKK activity and preserved IkappaBalpha in colon tissue.

CONCLUSIONS AND IMPLICATIONS

TFDG exerts protective effects in experimental colitis and inhibits production of inflammatory mediators through a mechanism that, at least in part, involves inhibition of NF-kappaB activation.

Black tea--helpful or harmful? A review of the evidence

OBJECTIVE

To consider whether consumption of black tea has a positive or negative impact on health.

DESIGN

Databases were searched for relevant epidemiological and clinical studies published between 1990 and 2004.

RESULTS

Clear evidence was found for coronary heart disease (CHD), where an intake of > or = 3 cups per day related to risk reduction. The mechanism could involve the antioxidant action of tea polyphenols. While experimental models have suggested that flavonoids attenuated cancer risk, epidemiological studies failed to demonstrate a clear effect for tea, although there is moderate evidence for a slightly positive or no effect of black tea consumption on colorectal cancer. Studies on cancer were limited by sample sizes and insufficient control of confounders. There is moderate evidence suggestive of a positive effect of black tea consumption on bone mineral density although studies were few. There is little evidence to support the effect of tea on dental plaque inhibition but evidence to support the contribution of tea to fluoride intakes and thus theoretical protection against caries. There was no credible evidence that black tea (in amounts typically consumed) was harmful. Normal hydration was consistent with tea consumption when the caffeine content was < 250 mg per cup. A moderate caffeine intake from tea appeared to improve mental performance, although sample sizes were small. There was no evidence that iron status could be harmed by tea drinking unless populations were already at risk from anaemia.

CONCLUSIONS

There was sufficient evidence to show risk reduction for CHD at intakes of > or = 3 cups per day and for improved antioxidant status at intakes of one to six cups per day. A maximum intake of eight cups per day would minimise any risk relating to excess caffeine consumption. Black tea generally had a positive effect on health.

Neuroprotective and neurorescue effect of black tea extract in 6-hydroxydopamine-lesioned rat model of Parkinson's disease

In the present study, an attempt has been made to explore the neuroprotective and neuroreparative (neurorescue) effect of black tea extract (BTE) in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD). In the neuroprotective (BTE + 6-OHDA) and neurorescue (6-OHDA + BTE) experiments, the rats were given 1.5% BTE orally prior to and after intrastriatal 6-OHDA lesion respectively. A significant recovery in d-amphetamine induced circling behavior (stereotypy), spontaneous locomotor activity, dopamine (DA)-D2 receptor binding, striatal DA and 3-4 dihydroxy phenyl acetic acid (DOPAC) level, nigral glutathione level, lipid peroxidation, striatal superoxide dismutase and catalase activity, antiapoptotic and proapoptotic protein level was evident in BTE + 6-OHDA and 6-OHDA + BTE groups, as compared to lesioned animals. BTE treatment, either before or after 6-OHDA administration protected the dopaminergic neurons, as evident by significantly higher number of surviving tyrosine hydroxylase immunoreactive (TH-ir) neurons, increased TH protein level and TH mRNA expression in substantia nigra. However, the degree of improvement in motor and neurochemical deficits was more prominent in rats receiving BTE before 6-OHDA. Results suggest that BTE exerts both neuroprotective and neurorescue effects against 6-OHDA-induced degeneration of the nigrostriatal dopaminergic system, suggesting that possibly daily intake of BTE may slow down the PD progression as well as delay the onset of neurodegenerative processes in PD.

Therapeutic effect of green tea extract on oxidative stress in aorta and heart of streptozotocin diabetic rats

Hyperglycemia induced oxidative stress has been proposed as a cause of many complications of diabetes including cardiac dysfunction. The present study depicts the therapeutic effect of green tea extract on oxidative stress in aorta as well as heart of streptozotocin diabetic rats. Six weeks after diabetes induction, green tea was administered orally for 4 weeks [300 mg (kg body weight)(-1) day (-1)]. In aorta and heart of diabetic rats there was a significant increase in the activity of superoxide dismutase, catalase and glutathione peroxidase with an increase in lipid peroxides. Diabetic rats showed a significant decrease in the levels of serum and cardiac glutathione. Green tea administration to diabetic rats reduced lipid peroxides and activity of antioxidant enzymes whereas increased glutathione content. The results demonstrate that the induction of antioxidant enzymes in diabetic rats is not efficient and sufficient to reduce the oxidative stress. But green tea by providing a competent antioxidative mechanism ameliorates the oxidative stress in the aorta and heart of diabetic rats. The study suggests that green tea may provide a useful therapeutic option in the reversal of oxidative stress induced cardiac dysfunction in diabetes mellitus.

Beneficial effects of tea and its polyphenols against prostate cancer

Tea, next to water, is the most widely consumed beverage in the world. Depending upon the level of fermentation, tea can be categorized into three types: green (unfermented), oolong (partially fermented), and black (highly to fully fermented). In general, green tea has been found to be superior to black and oolong tea in terms of antioxidant and health promoting benefits owing to the higher content of (-)-epigallocatechin-3-gallate. Tea polyphenols comprise about one-third of the weight of the dried leaf, and they exhibit biochemical and pharmacological activities including antioxidant activities, inhibition of cell proliferation, induction of apoptosis, cell cycle arrest and modulation of carcinogen metabolism. Several studies demonstrate that most tea polyphenols exert their effects by scavenging reactive oxygen species (ROS) since excessive production of ROS has been implicated in the development of a variety of ailments including cancer of the prostate gland (CaP). Using cell culture and animal model systems, molecular targets for these remarkable beneficial effects of green tea drinking on CaP prevention and therapy have been defined. Geographical and case-control studies are showing that green tea drinking could afford CaP chemopreventive effects in human population. In this review we attempt to summarize the experimental as well as the epidemiological basis for the possible role of tea and its polyphenols for chemoprevention and chemotherapy of CaP.

Green tea polyphenol epigallocatechin-3-gallate differentially modulates oxidative stress in PC12 cell compartments

Tea polyphenols have been reported to be potent antioxidants and beneficial in oxidative stress related diseases. Prooxidant effects of tea polyphenols have also been reported in cell culture systems. In the present study, we have studied oxidative stress in the subcellular compartments of PC12 cells after treatment with different concentrations of the green tea polyphenol, epigallocatechin-3-gallate (EGCG). We have demonstrated that EGCG has differentially affected the production of reactive oxygen species (ROS), glutathione (GSH) metabolism and cytochrome P450 2E1 activity in the different subcellular compartments in PC12 cells. Our results have shown that although the cell survival was not inhibited by EGCG, there was, however, an increased DNA breakdown and activation of apoptotic markers, caspase 3 and poly- (ADP-ribose) polymerase (PARP) at higher concentrations of EGCG treatment. Our results suggest that the differential effects of EGCG might be related to the alterations in oxidative stress, GSH pools and CYP2E1 activity in different cellular compartments. These results may have implications in determining the chemopreventive therapeutic use of tea polyphenols in vivo.