Black Tea (Camellia sinensis) as a Chemopreventive Agent in Oral Precancerous Lesions

Oral carcinoma is the most common malignancy found in adult Indian men and the third most common in adult Indian women. About half of all cases are found to be associated with precancerous lesions, chiefly leukoplakia. We wanted to explore the possible benefits of black tea (Camellia sinensis) administered to patients with oral leukoplakia. Eighty-two subjects with oral leukoplakia underwent micronuclei and chromosomal assays on exfoliated oral mucosal epithelium, after which they received black tea in a fixed regimen. The micronuclei assay was repeated at 6 months, and the chromosomal study at 1 year. After the first year, the first 15 patients entered onto this study showed a significant decrease in the micronuclei frequency and chromosomal aberrations, which correlated with the clinical improvement. Several in vitro and animal studies have suggested the efficacy of tea in the chemoprevention of cancer. To the best of our knowledge, this is the first report on the effect of black tea in oral leukoplakia.

Black Tea Protects Thymocytes in Tumor-Bearing Animals by Differential Regulation of Intracellular ROS in Tumor Cells and Thymocytes

The accumulated in vitro evidence indicates that many tumors induce T-cell apoptosis as a mechanism of inhibiting antitumor activity. This downregulation of cell-mediated immune functions occurring at the late stages of the disease may be causally related to the thymic involution, because the thymus is the major site of T-cell maturation, extensive proliferation, and differentiation. Our results showed that in Erhlich's ascites carcinoma cell (EAC)-bearing mice, the number of EAC was inversely proportional to the thymocyte count in the host's thymus, which is the primary immune organ. Further studies indicated the presence of tumor-induced thymocyte apoptosis in EAC bearers. Black tea prolonged the survival of the tumor bearer by successfully restricting tumor progression as well as protecting the thymus from tumor insult. In fact, black tea inhibited thymic apoptosis while inducing programmed cell death of EAC. Interestingly, the tea regulated the oxidant status differentially in EAC and thymocytes--i.e., it reduced the EAC-induced reactive oxygen species (ROS) generation in the thymus while activating the same in the EAC. A similar effect of black tea was obtained when thymocytes were cultured in the presence of cell-free ascitic fluid, thereby indicating that black tea could directly reduce oxidative stress, an activity independent of its tumoricidal property. As a result, the maturation block in thymocyte subpopulations in tumor bearers was ameliorated significantly in black tea-treated animals. Our results demonstrate that black tea protects thymocytes in the tumor bearer by regulating the intracellular ROS in tumor cells and thymocytes differentially, thereby strengthening its candidacy in future anticancer therapeutic regimens.

In vitro antimycotic activity of some plant extracts towards yeast and yeast-like strains

As part of screening aimed at the selection of novel antimycotic compounds of vegetable origin, leaf extracts of Camellia sinensis L., Cupressus sempervirens L. and Pistacia lentiscus L. and the seed extract of Glycine soja Sieb. et Zucc. were tested against yeast and yeast-like species implicated in human mycoses. Of the extracts only those of C. sinensis (obtained from a commercial preparation of green tea) exhibited broad activity towards Candida glabrata, Clavispora lusitatiae, Cryptococcus laurentii, Filobasidiella neoformans, Issatchenkia orientalis, Saccharomyces cerevisiae and Prototheca wickerhamii strains. MICs ranging from 300 to 4800 microg extract/mL (corresponding to 130-2010 microg/mL total polyphenols) were observed. Concentrations of the C. sinensis extract over 25 000 microg/mL caused a rapid decrease of viable cells of Fil. neoformans and its activity was dose-dependent. Tests carried out using the pure polyphenols present in C. sinensis extract composition, showed that only epicatechin-3-O-gallate (ECG) and epigallocatechin-3-O-gallate (EGCG) possess antimycotic activity.

Antioxidant Potential of Black Tea Against 7,12-Dimethylbenz(a)anthracene- Induced Oxidative Stress in Swiss Albino Mice

Oxygen free radicals and related reactive species have been implicated in the etiology of many diseases, such as atherosclerosis, neurodegenerative disorders, and cancer. Antioxidant enzymes exist in cells to protect against the effects of these free radicals and other oxygen-derived species, which are produced during the oxidative stress. Tea (Camellia sinensis) is the most commonly consumed beverage worldwide. Both green and black tea are known to possess many pharmacological properties, including antioxidant, antipyretic, antibacterial, and antineoplastic effects. In the present study, the preventive effects of black tea extract (BTE) was evaluated in Swiss albino mice against 7,12-dimethyl benz(a)anthracene (DMBA)-induced oxidative stress. The animals were given 0.5%, 1%, and 1.5% BTE as the sole source of drinking solution for 1 week prior to the administration of DMBA, which was given orally as a single dose of 50 mg/kg body weight. At the end of the study period, the liver, kidney, and prostate tissues were dissected out for the determination of antioxidant enzyme levels (catalase, superoxide dismutase, glutathione reductase, glutathione-S-transferase), and lipid peroxidation. A dose-dependent protective effect of BTE against DMBA-induced depletion in enzymes activity was observed in all three tissues examined. Similarly, a significant dose-dependent inhibition of the lipid peroxidation caused by DMBA was observed in the BTE-administered animals in all three tissues examined. Our results revealed that BTE provides protection against oxidative damage induced by xenobiotics.

Transactivation of peroxisome proliferator-activated receptor alpha by green tea extracts

Tea is a popular beverage. Recently, green tea was reported to increase the number of peroxisomes in rats. In this study, to find out whether the green tea-induced proliferation of peroxisomes is mediated by PPARalpha , a transient transfection assay was carried out to investigate the interactions of tea extracts (green tea, black tea,oolong tea and doongule tea) and tea components (epigallocatechin gallate, epigallocatechin, epicatechin gallate, epicatechin and gallic acid), with mouse cloned PPARalpha . Green tea and black tea extracts, and epigallocatechin gallate, a major component of fresh green tea leaves, increased the activation of PPAalpha 1.5-2 times compared with the control. It is suggested that the green tea induced-peroxisomal proliferation may be mediated through the transactivation of PPARalpha and that epigallocatechin gallate may be an effective component of green tea leaves. This would account for the increase in the number of peroxisomes and the activity of peroxisomal enzymes previously reported. However, black tea, a fully fermented product, had a stronger effect than oolong tea extract. These results also suggest, that in addition to epigallocatechin gallate, green tea leaves may possess some active chemicals newly produced as a result of the fermentation process, which act on PPARalpha like other peroxisome proliferators.

In vitro anti-?-secretase and dual anti-cholinesterase activities ofCamellia sinensis L. (tea) relevant to treatment of dementia

The primary target of licensed drugs for the treatment of Alzheimer's disease is the inhibition of the enzyme acetylcholinesterase, although preventing beta-amyloidosis is a prime target for drugs in development. The in vitro dual anti-cholinesterase and beta-secretase activities of Camellia sinensis L. extract (tea) is reported. Green and black tea inhibited human acetylcholinesterase (AChE) with IC(50) values of 0.03 mg/mL and 0.06 mg/mL respectively, and human butyrylcholinesterase (BuChE) with IC(50) values 0.05 mg/mL. Green tea at a final assay concentration of 0.03 mg/mL inhibited beta-secretase by 38%. These novel findings suggest that tea infusions contain biologically active principles, perhaps acting synergistically, that may be used to retard the progression of the disease assuming that these principles, yet to be identified, reach the brain.

In vitro Cytotoxicity of Epigallocatechin Gallate and Tea Extracts to Cancerous and Normal Cells from the Human Oral Cavity

This study compared the in vitro responses of malignant and normal cells from the human oral cavity to tea extracts and to its main polyphenolic component, (-)-epigallocatechin gallate (EGCG). The antiproliferative effects of tea polyphenolic extracts and EGCG were more pronounced towards immortalized, tumourigenic (CAL27, HSC-2, and HSG(1)) and non-tumourigenic (S-G) cells than towards normal (GN56 and HGF-1) fibroblasts and green tea was more toxic than black tea. As the addition of tea extract or EGCG to cell culture medium led to the formation of hydrogen peroxide (H(2)O(2)), the research then focused on EGCG as an inducer of oxidative stress, using CAL27, the cancerous cells most sensitive to EGCG, HSG(1), the cancerous cells least sensitive to EGCG, and GN56 cells. The toxicity of EGCG was decreased in the presence of catalase, an enzyme that degrades H(2)O(2), or of deferoxamine, a chelator of Fe(3+). Conversely, pretreatment of the cells with the glutathione depleters, 1-chloro-2,4-dinitrobenzene and 1,3-bis(2-chloroethyl)-N-nitrosourea, potentiated the toxicity of EGCG. A 4-hr exposure to EGCG lessened the intracellular level of reduced glutathione in the CAL27 and HSG(1) cells, but not in the GN56 fibroblasts. Whereas EGCG itself did not induce lipid peroxidation, Fe(2+)-induced lipid peroxidation was potentiated by EGCG. A 72-hr exposure to cytotoxic concentrations of EGCG induced significant cytoplasmic vacuolization in all cell types. The results presented herein are consistent with EGCG acting as a prooxidant, with the cancerous cells more sensitive to oxidative stress than the normal cells.

An ex-vivo angiogenesis assay as a screening method for natural compounds and herbal drug preparations

Angiogenesis is a fundamental component of complex biological processes, including oncogenesis. The aim of this work was to optimise and validate an ex-vivo angiogenesis assay as a quantitative (PC image) biological method for testing promising natural compounds and herbal drug preparations for their pro-/anti-angiogenic activity. The bioassay is based on the principle of wound healing and quantifies the effect of angiogenic agents on neovessel outgrowth of human placental vessels embedded in a three-dimensional fibrin matrix. The assay was validated by using known, well characterised pro- and anti-angiogenic effectors (basic fibroblast growth factor and carboxyamidotriazole, respectively), and an angiogenesis inhibitor of plant origin (green tea leaves extract) was used as a reference product to demonstrate the applicability of the assay for plant extracts. Other standardised plant extracts prepared from olive tree leaves and horse chestnut seeds were tested for their angiogenic potential, but showed only slight inhibitory or no activity, respectively. The results presented here indicate that this human ex-vivo angiogenic assay is "ready to use" for screening of herbal drug preparations and pure compounds.

In vitro transdermal delivery of the major catechins and caffeine from extract of Camellia sinensis

The aim of this study was to investigate the feasibility of the transdermal delivery of catechins and caffeine from green tea extract. Drug-in-adhesive patches containing 1.35, 1.03, 0.68, and 0.32 mg cm(-2) green tea extract were formulated and the dissolution of (-)-epigallocatechin gallate (EGCg), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC) from these was determined. Transdermal delivery was determined across full thickness pig ear skin from saturated solutions of green tea extract in pH 5.5 citrate-phosphate buffer, polyethylene glycol 400 and a 50:50 mixture of the citrate phosphate buffer and polyethylene glycol in addition to patches containing 1.35 mg cm(-2) green tea extract. Dissolution experiments indicated first order release which was dose dependent in respect of the loading level, although the amounts permeated were not always proportional to the amounts in the formulation. The highest percentage permeation of EGCg was found to be from the patch formulation. EGCg, EGC and EC were all successfully delivered transdermally from saturated solutions and adhesive patches containing green tea extract in this study. There was some evidence for the dermal metabolism of EGCg, but after 24 h 0.1% permeated from the patches containing 1.35 mg cm(-2) green tea extract. This was equivalent to the percentage absorbed after intragastric administration of green tea extract in rats. In addition, the concentration of EGCg in the Franz cell receptor chamber after 24 h permeation from the 0.9 cm diameter patch containing 1.35 mg cm(-2) was within the range of Cmax plasma levels achieved after oral dosing of 2.2-4.2 gm(-2) green tea extract. Caffeine was also delivered at concentrations above those previously reported.

The In Vivo Effects of Cytokines Modulation for BALB/C Mice Fed with a Traditional Combined Chinese Herb‐Soaked Solution, Yi‐Fey Ruenn‐Hou Tea

An experiment was conducted to investigate the effects of Yi-Fey Ruenn-Hou (YR) Tea, a combination of Chinese herbs, 10% licorice root, 10% American ginseng, 10% Radix Paeoniae alba and 70% green tea-soaked solution, on the cytokine modulation in Balb/C mice. Four groups of mice were administered either 1ml of drinking water (group A) or 2 mg/ml (group B), 8 mg/ml (group C), 40 mg/ml (group D) of a saturated solution of combined Chinese herbs daily for six months. The physiological and pathological characteristics of the mice were observed during the time, and the mice were weighed and at least two mice were sacrificed each month for pathological detection of the brain, heart, liver, spleen and kidney and cytokine analysis. The results revealed neither weight difference nor pathological change among the four groups, however, serum-cytokine assay indicated that the cytokine modulation effects are consistent, and the most obvious cytokine modulation effect was observed in group D, which was the highest dosage employed for treating the mice. TH2-pattern cytokines responded earlier and higher in group D than in groups B and C. Furthermore, the effect of YR Tea on cytokine modulation in vivo is predominantly TH2-pattern and is dependent on its dosage (P < 0.05).

Growth inhibition and cell cycle arrest effects of epigallocatechin gallate in the NBT-II bladder tumour cell line

OBJECTIVES

To examine the growth inhibition and cell cycle arrest effects of epigallocatechin gallate (EGCG), a major constituent of green tea polyphenols, on the NBT-II bladder tumour cell line.

MATERIALS AND METHODS

Growth inhibition and cell cycle arrest effects of EGCG were evaluated by the tetrazolium assay, flow cytometry and apoptotic DNA ladder tests. The cell cycle-related oncogene and protein expressions in NBT-II bladder tumour cells, when incubated with EGCG, were detected with reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis.

RESULTS

EGCG inhibited growth of the NBT-II bladder tumour cells in a dose- and time-dependent manner. Flow cytometry showed a G0/G1 arrest in cells when cultured with EGCG at doses of 10, 20 or 40 micro mol/L for 48 or 72 h. The apoptotic DNA ladder test showed that EGCG at 10 micro mol/L induced early apoptosis after 48 h of incubation. A down-regulation of cyclin D1 was detected by RT-PCR when the cells were incubated with EGCG (20 micro mol/L for 48 h. EGCG also down-regulated protein expression of cyclin D1, cyclin-dependent kinase 4/6 and phosphorylated retinoblastoma protein, in both a time- and dose-dependent manner, when detected by Western blot.

CONCLUSION

EGCG had growth inhibition and cell-cycle arrest effects in NBT-II bladder tumour cells by down-regulating the cyclin D1, cyclin-dependent kinase 4/6 and retinoblastoma protein machinery for regulating cell-cycle progression.

Inhibitory effects on phospholipase A2 and antivenin activity of melanin extracted from Thea sinensis Linn

Antivenin activity of melanin extracted from black tea (MEBT) was reported for the first time. The antagonistic effect of MEBT was evaluated for Agkistrodon contortrix laticinctus (broadbanded copperhead), Agkistrodon halys blomhoffii (Japanese mamushi), and Crotalus atrox (western diamondback rattlesnake) snake venoms administered i.p. to ICR mice. MEBT was injected i.p. immediately after the venom administration in dose of 3 mg per mouse in the same place of venom injection. MEBT demonstrated neutralization effect against all venoms tested. The greatest antivenin effect of MEBT was found against Japanese mamushi snake venom. In this case, half the mice died within 2.5 +/- 0.7 h after injection of 0.9 mg/kg of venom. An immediate injection of MEBT substantially reduced the toxic effect of venom and extended time at the 50% level of survival up to 52.3 +/- 2.3 h. The antivenin activity of MEBT is due to chelating of Ca++ and non-specific binding of phospholipase A2. The inhibitory effect of MEBT on phospholipase A2 assessed for different venoms was similar to that obtained with pure enzyme. Low toxicity of MEBT in combination with its antagonistic activity against different venoms may allow effective life-saving treatment against snakebites. Such application of MEBT is important when identification of the snake is impossible or if specific treatment is unavailable.

Antimicrobial activity of 3-O-acyl-(-)-epicatechin and 3-O-acyl-(+)-catechin derivatives

As an exploratory investigation of antimicrobial promoting compounds, 3- O-acyl-(-)-epicatechins and 3- O-acyl-(+)-catechins possessing various aromatic groups and aliphatic chains of varying length from C4 to C16 for increasing lipophilicity were synthesized and tested for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi. The (-)-epicatechin and (+)-catechin derivatives comprised of aromatic groups increased activity and derivatives with acyl chain groups of carbon atoms in the close vicinity of C8 to C10 showed strong antimicrobial activity (MIC = 2 - 8 microg/ml) against Gram-positive bacteria and weak activity against fungi. However, the activity decreased when the carbon chain length of the substituents was too short (C4 to C6) or too long (C16). These results suggest that the presence of lipophilic substituents with moderate sizes might be crucial for the optimal antimicrobial activity.

Anti-inflammatory activity of tea (Camellia sinensis) root extract

Pharmacological studies were carried out with methanol-water (1:1) extract of dried tea (Camellia sinensis) root extract (TRE). TRE was found to possess anti-inflammatory, analgesic and antipyretic activities at 1/10th of its LD50 dose of 100 mg/kg i.p. It was found that TRE inhibited the arachidonic acid-induced paw oedema in rats which indicated that TRE produced the anti-inflammatory activity by inhibiting both the cyclooxygenase and lypooxygenase pathways of arachidonic acid metabolism. TRE also enhanced peritoneal cell count and the number of macrophages in normal mice. It is plausible that the saponins present in TRE may be responsible for these activities of TRE.

Green tea as an antioxidant which protects against alcohol induced injury in rats -- a histopathological examination

Our study with animal models was designed to test the hypothesis that green tea protects against chronic (over 4 weeks) alcohol induced liver injury in rats. The research was conducted on Wistar male rats divided into 4 research groups: I - received the Libera-De Carli control diet (L-DC), II - received (L-DC) and green tea, III - received (L-DC) and ethanol and IV - received (L-DC), green tea and ethanol. When comparing groups I and II we saw less intensive steatosis in group II than in group I, which can suggest that green tea may affect the accumulation of fat in the hepatocytes and protect them against steatosis and disruption. In III, the ethanol group, the steatosis of the liver increased considerably and the green tea which was given with ethanol in group IV did not halt this, as in group IV we also observed intensive steatosis in the liver. From this data we conclude that green tea has an important, although not fully understood role in preventing liver injury.

Inhibitory effect of green tea catechins in combination with sucralfate on Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

The occurrence of antibiotic-resistant Helicobacter pylori has been reported. It is desirable to develop an effective method to prevent the occurrence of resistant strains of Helicobacter pylori. Green tea catechins (GTCs) have been reported to have an antibacterial effect. Therefore, the possibility of eradicating Helicobacter pylori by the oral administration of GTCs was investigated.

METHODS

Solutions of GTCs and solutions of GTCs adsorbed to sucralfate (GTC-scf), at concentrations of 20 mg GTCs and/or 20 mg sucralfate/ml were prepared. Then 1 ml of the GTC-scf or the GTC solution was administered daily, for 10 days to Mongolian gerbils infected with Helicobacter pylori. Then the stomachs were extirpated and homogenized. The homogenate was spread on selective medium plates. After 5-day culture, colony-forming units (CFU) of Helicobacter pylori were counted.

RESULTS

The CFU of Helicobacter pylori was significantly decreased by GTC-scf.

CONCLUSIONS

GTC-scf may have a bactericidal effect on Helicobacter pylori infection.

Green tea protects against ethanol-induced lipid peroxidation in rat organs

Ethanol metabolism is accompanied by generation of free radicals, which stimulates lipid peroxidation. Natural antioxidants are particularly useful in such a situation. The current study was designed to investigate the efficacy of green tea, as a source of water-soluble antioxidants (catechins), on lipid peroxidation in liver, brain, and blood induced by chronic (4 weeks) ethanol intoxication in rats. Feeding of ethanol led to a significant increase in lipid peroxidation, as measured by increased concentrations of lipid hydroperoxides, 4-hydroxynonenal, and malondialdehyde. Feeding of ethanol also changed the glutathione-dependent lipid hydroperoxide decomposition system, resulting in a decrease in both reduced glutathione concentration and activity of glutathione peroxidase. Observed changes were statistically significant in all examined tissues. Enhancement in lipid peroxidation was associated with disruption of hepatocyte cell membranes, as observed through electron microscopic evaluation. Green tea protects phospholipids from enhanced peroxidation and prevents changes in biochemical parameters and morphologic changes observed after ethanol consumption. These results support the suggestion that green tea protects membranes from peroxidation of lipids associated with ethanol consumption.

Evidence for a prospective anti-osteoporosis effect of black tea (Camellia Sinensis) extract in a bilaterally ovariectomized rat model

The purpose of this study was to examine whether whole aqueous black tea extract (BTE) prevents bone loss induced by ovarian hormone deficiency. Eighteen 95-100 days old female albino rats were randomly assigned to three treatment groups [sham -operated control (sham); bilaterally ovariectomized (ovx) and ovx + aqueous black tea extract (BTE) ] and sacrificed after 28 days. All animals were fed a standard laboratory diet with free access to deionized water except on days of urinary parameter studies when animals were given only calcium free deionized water during the entire 24 h period of urine collection. Body weight study revealed that rats in the ovx group had significantly higher final body weight than rats in the sham group. This higher final body weight was not observed in animals receiving BTE. The ovx group also had significantly higher abdominal fat mass and liver weight and significantly lower uterus, right kidney and left kidney weights than in other two groups. All these organ weight changes in ovx group also were not observed in animals receiving BTE. Results of urinary studies revealed that rats in the ovx group had significantly higher urinary excretion of calcium (Ca), phosphate, creatinine (Cr), calcium to creatinine (Ca:Cr) ratio (P< 0.001) and hydroxyproline (HPr) (P< 0.01) than rats in the sham group. Significant recovery of all these parameters were observed in animals receiving BTE. The ovx group also had significantly higher (P< 0.001) serum alkaline phosphatase (AP) and tartrate-resistant acid phosphatase (TRAP) activity than rats in the other two groups. These changes could not be seen in animals receiving BTE. Also, identical changes were seen in bone density experiments. Rats in the ovx group had significantly lower densities of the right femur (P<0.001), eighth thoracic rib (P< 0.001), eighth thoracic vertebra (P< 0.05), and fourth lumbar vertebra (P< 0.01) than rats in the sham group; and significant improvement in densities of these bones were seen in animals supplemented with BTE. Animals of ovx group also showed significant decrease in calcium and phosphate level in all these bones which could be regained significantly when these animals were supplemented with BTE. Our findings suggest that aqueous BTE may be effective in preventing bone loss due to ovarian hormone deficiency. Because serum activity of AP, TRAP and urinary loss of bone minerals (Ca and Phosphate) and also the organic components of bone (Cr and HPr) were significantly greater in the ovx group, compared to sham animals and ovx + BTE group. This confirms that ovariectomy enhances and BTE suppresses the rate of bone turnover. The density results of ovx + BTE group are significantly greater than rats in the ovx group, suggesting further that formation exceeded resorption. Detailed studies are underway to clarify the mechanism of this protective effect of BTE on hypogonadal bone loss.

Black tea extract suppresses transformation of aryl hydrocarbon receptor induced by dioxin

Dioxins cause various adverse effects through binding to an aryl hydrocarbon receptor (AhR) and transformation of the receptor. In this study, we investigated whether black tea extract suppresses AhR transformation. Dried black tea leaves were extracted with 75% ethanol, and the extract was pretreated to the rat liver cytosol fraction 10 min prior to addition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Transformed AhR was detected by electrophoretic gel mobility shift assay. Black tea extract suppressed AhR transformation in a dose-dependent manner, and the IC50 value against 1 nM TCDD-induced AhR transformation was 8.9 microg/ml. The result suggests that intake of black tea has a potential to suppress the AhR transformation, leading protection from dioxin toxicity.

Antimutagenic effects of black tea in the Salmonella typhimurium reverse mutation assay

Black tea (Camellia sinensis) is one of the most widely consumed beverages worldwide. Its chemopreventive effects are well documented in the literature. In the present set of investigations antimutagenic effects of aqueous black tea extract (ATE) and black tea polyphenols (BTP) were evaluated in the Ames test using Salmonella typhimurium tester strains TA 98 and TA 100. Addition of benzo(a)pyrene (BaP) and cyclophosphamide (CP), two well known mutagens, at the concentrations of 20 and 15 microg/plate, respectively, in an S-9 metabolically activated system resulted in significant induction of his+ revertant colonies. However, addition of 500 microl 1, 2 and 4% ATE to the BaP and CP treated plates resulted in a dose dependent inhibition in the number of his+ revertant colonies. Furthermore in another set of experiments, supplementation with BTP at the concentrations of 100, 200 and 400 microg/plate also led to a significant inhibition in BaP and CP induced colony formation. The antimutagenic activity of BTP was found to be higher than that of ATE, which may be attributable to the higher amount of polyphenolic ingredients. Hence the study revealed that black tea has a protective efficacy in suppressing BaP and CP induced mutagenicity in a microbial test system.

Black tea consumption and risk of rectal cancer in Moscow population

PURPOSE

This population-based case-control study (663 cases and 323 controls) examined the effect of black tea intake on the risk of rectal cancer in Moscow residents. The Moscow population was selected for its wide range of black tea consumption.

METHODS

This study used three measures of tea consumption: the volume of beverage (l/month), zavarka (tea concentrate, l/month), and dry tea (g/month). We calculated the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for these three parameters of tea intake using logistic regression.

RESULTS

Greater use of dry tea was associated with lower risk of rectal cancer in women (high vs. low: OR = 0.40; 95% CI, 0.23-0.70) and in men (high vs. low: OR = 0.77; 95% CI, 0.42-1.43). The observed effect was weaker when tea was measured as zavarka (high vs. low in women: OR = 0.47; 95% CI, 0.26-0.83; in men: OR = 0.99; 95% CI, 0.52-1.96) and as beverage volume (high vs. low in women: OR = 0.68; 95% CI, 0.39-1.19; in men: OR = 1.03; 95% CI, 0.53-2.09).

CONCLUSIONS

These findings support the hypothesis that black tea consumption reduces the risk of rectal cancer. The attenuation of the effect across the three measures of tea intake can be explained by an increasing degree of exposure misclassification from dry tea to zavarka and beverage volume.

Reversal of cancer multidrug resistance by tea polyphenol in KB cells

Tea polyphenols, (-)-epigallocatechin gallate in particular, were examined for their modulating effects on the drug resistance KB-A-1 cells and drug sensitive KB-3-1 cells. Both KB-3-1 and KB-A-1 cells were equally sensitive to tea polyphenol and (-)-epigallocatechin gallate. When 10 microgram/ml (-)-epigallocatechin gallate or 40 microgram/ml tea polyphenol were present simultaneously with doxorubicin, the IC50 of doxorubicin on KB-A-1 cells decreased from 10.3 +/- 0.9 microgram/ml to 4.2 +/- 0.2 or 2.0 +/- 0.1 microgram/ml. Tea polyphenol and (-)-epigallocatechin gallate enhanced the cytotoxicity of doxorubicin on KB-A-1 cells by 5.2 and 2.5 times, respectively, but did not show a modulating effect on KB-3-1 cells. Both tea polyphenol and (-)-epigallocatechin gallate showed reversal effects on the multidrug resistance phenotype.

Preventive effects of urinary bladder tumors induced by N-butyl-N-(4-hydroxybutyl)-nitrosamine in rat by green tea leaves

BACKGROUND

Recently, the anticarcinogenic effects of green tea have been studied in sites other than the urinary tract. Although the incidence of bladder cancer has increased, responses to therapy have been limited. The present work examined the preventive effects of green tea against bladder tumors induced in rats by the carcinogen, N-butyl-N-(4-hydroxybutyl)-nitrosamine(BBN).

METHODS

From week 5 to week 9, all the groups were exposed to 0.05% BBN in the drinking water for 5 weeks. Rats were divided into four groups. Group 1 was fed a CE-2 diet and tap water for the entire experimental period and served as the control group. Group 2 was fed the green tea leaves after carcinogen exposure. Groups 3 and 4 received green tea leaves before carcinogen exposure. All rats were killed and examined at 44 weeks.

RESULTS

Green tea leaves prevented the growth of BBN-induced urinary bladder tumors when given before the carcinogen.

CONCLUSION

Green tea may inhibit tumor initiation in the bladder.

Indonesian medicinal plants. XXV. Cancer cell invasion inhibitory effects of chemical constituents in the parasitic plant Scurrula atropurpurea (Loranthaceae)

Six fatty acids (1-6), two xanthines (7, 8), two flavonol glycosides (9, 10), one monoterpene glucoside (11), one lignan glycoside (12), and four flavanes (13-16) were clarified by a bioassay-guided separation as chemical constituents of Scurrula atropurpurea (Loranthaceae), a parasitic plant of the tea plant Thea sinensis (Theaceae). Among these constituents, it was found that the alkynic fatty acid octadeca-8,10,12-triynoic acid (6) exhibits a more potent inhibitory effect on cancer cell invasion in vitro than flavanes [(+)-catechin (13), (-)-epicatechin (14), (-)-epicatechin-3-O-gallate (15) and (-)-epigallocatechin-3-O-gallate (16)].