Green tea extract and aromatase activity
Green tea extract has been found to inhibit aromatase activity in male rats. (Aromatase is an enzyme that converts androgens to estrogens.) A recent study administered green tea extract catechins to male rats for two, four and eight weeks, starting at age five weeks. It was found that a 5% dose to male rats for two to eight weeks induced goiters and decreased weights of the body, testis and prostate gland. The treatment elevated circulating thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels, and decreased tri-iodothyronine and thyroxine levels (hormones secreted by the thymus gland). Green tea exhibited inhibitory effects on human placental aromatase activity. The endocrinological changes in the body were anti-thyroid effects and aromatase inhibition due to the effects of green tea extract and its components.
FOOD AND CHEMICAL TOXICOLOGY, 2002, Vol 40, Iss 7, pp 925-933
Green tea benefits digestive tract
Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage is excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved with 100 mg of tea catechins (equivalent to two to five cups of green tea) three times daily with meals for three weeks. When catechin administration ceased, the effects reversed after one week. Catechins should be considered further in colon carcinogenesis studies.
JOURNAL OF CELLULAR BIOCHEMISTRY, 1997, Suppl. 27, pp 52-58
The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. The heat resistance of B stearothermophilus spores (a thermophilic spore-forming bacterium) was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. Epigallocatechin gallate, the main component of tea polyphenols, showed strong activity against both B stearothermophilus and C thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.
JOURNAL OF BIOSCIENCE AND BIOENGINEERING, 2000, Vol 90, Iss 1, pp 81-85
Green tea protects against alcohol-induced liver injury
A study examined the antioxidant polyphenolic extract of green tea against early alcohol-induced liver injury. Rats were fed high-fat liquid diets with or without alcohol and green tea (300 mg kg/day) continuously for four weeks. After four weeks, the blood ALT (sign of liver damage) levels were increased significantly from 35 to 114 (four-fold over placebo group values). However, the inclusion of green tea extract in the diet significantly blunted the increase to 65. The alcohol also caused severe fatty accumulation, mild inflammation and tissue death in the liver. However, with green tea extract, the increase in tissue death caused by alcohol were significantly reduced, while not affecting fat accumulation or inflammation. Alcohol also significantly increased the accumulation of protein adducts (products of lipid peroxidation and an indication of oxidative stress). However, green tea extract blocked this effect almost completely. Green tea extract also blunted the increase of TNFalpha (causes inflammation) protein levels in the liver by alcohol. The results indicate that dietary antioxidants, such as those found in green tea, prevent early alcohol-induced liver injury, most likely by preventing free radical stress.
BIOLOGICAL CHEMISTRY 2002;383(3-4):663-70
Green tea, grape juice, and colon cancer
Full source: BIOLOGICAL & PHARMACEUTICAL BULLETIN, 2000, Vol 23, Iss 6, pp 695-699
A study reported the effects of tea and juice on the activity of the intestines. Green tea strongly inhibited the E. coli-expressed mouse intestinal phenol sulfotransferases (P-STs) activity in vitro. The active component of green tea, (-)-Epigallocatechin gallate (EGCG), was found to be the most potent inhibitor among the catechins tested. (-)EGCG also inhibited the P-ST activity of the human colon cancer cells. Among fruit juices examined (apple, grape, grapefruit and orange), grape juice exhibited the most potent inhibitory action on the P-ST activity of mouse intestines and human colon cancer cells. The inhibitory activity of grape juice was located mainly in the skin and seeds. Flavonols, such as quercetin and kaempferol, inhibited the P-ST activity at low concentrations. The results suggest the possible inhibition of P-ST activity in human intestines by green tea or grape juice.
Curr Med Chem Anti-Canc Agents 2002 Jul;2(4):441-63 Related Articles, Links
Green tea catechins as novel antitumor and antiangiogenic compounds.
Demeule M, Michaud-Levesque J, Annabi B, Gingras D, Boivin D, Jodoin J, Lamy S, Bertrand Y, Beliveau R.
Laboratoire de Medecine Moleculaire, UQAM-Hocric;pital Sainte-Justine, Montreal, Canada.
[email protected]
The concept of cancer prevention by use of naturally occuring substances that could be included in the diet is under investigation as a practical approach towards reducing cancer incidence, and therefore the mortality and morbidity associated with this disease. Tea, which is the most popularly consumed beverage aside from water, has been particularly associated with decreased risk of various proliferative diseases such as cancer and atherosclerosis in humans. Various studies have provided evidence that polyphenols are the strongest biologically active agents in green tea. Green tea polyphenols (GTPs) mainly consist of catechins (3-flavanols), of which (-)-epigallocatechin gallate is the most abundant and the most extensively studied. Recent observations have raised the possibility that green tea catechins, in addition to their antioxidative properties, also affect the molecular mechanisms involved in angiogenesis, extracellular matrix degradation, regulation of cell death and multidrug resistance. This article will review the effects and the biological activities of green tea catechins in relation to these mechanisms, each of which plays a crucial role in the development of cancer in humans. The extraction of polyphenols from green tea, as well as their bioavailability, are also discussed since these two important parameters affect blood and tissue levels of the GTPs and consequently their biological activities. In addition, general perspectives on the application of dietary GTPs as novel antiangiogenic and antitumor compounds are also presented.
PMID: 12678730 [PubMed - in process]
Kidney Int 2003 May;63(5):1785-1790 Related Articles, Links
Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat.
Priyadarshi S, Valentine B, Han C, Fedorova OV, Bagrov AY, Liu J, Periyasamy SM, Kennedy D, Malhotra D, Xie Z, Shapiro JI.
The Departments of Medicine and Pharmacology Medical College of Ohio, Toledo, Ohio; The Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medical Sciences, Beijing, China; and Laboratory of Cardiovascular Science,National Institute on Aging, National Institutes of Health, Baltimore, Maryland.
Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat. BACKGROUND: Left ventricular hypertrophy commonly complicates chronic renal failure. We have observed that at least one pathway of left ventricular hypertrophy appears to involve signaling through reactive oxygen species (ROS). Green tea is a substance that appears to have substantial antioxidant activity, yet is safe and is currently widely used. We, therefore, studied whether green tea supplementation could attenuate the development of left ventricular hypertrophy in an animal model of chronic renal failure. METHODS: Male Sprague-Dawley rats were subjected to sham or remnant kidney surgery and given green tea extract (0.1% and 0.25%) or plain drinking water for the next 4 weeks. Heart weight, body weight, and cardiac Na-K-ATPase activity were measured at the end of this period. To further test our hypothesis, we performed studies in cardiac myocytes isolated from adult male Sprague-Dawley rats. We measured the generation of ROS using the oxidant sensitive dye dichlorofluorescein (DCF) as well as (3H)phenylalanine incorporation following exposure to cardiac glycosides with and without green tea extract. RESULTS: Administration of green tea extract at 0.25% resulted in attenuation of left ventricular hypertrophy, hypertension, and preserved cardiac Na-K-ATPase activity in rats subjected to remnant kidney surgery (all P < 0.01). In subsequent studies performed in isolated cardiac myocytes, both ouabain and marinobufagenin (MBG) were both found to increase ROS production and (3H)phenylalanine incorporation at concentrations substantially below their inhibitor concentration (IC) 50 for the sodium pump. Addition of green tea extract prevented increases in ROS production as well as (3H)phenylalanine incorporation in these isolated cardiac myocytes. CONCLUSION: Green tea extract appears to block the development of cardiac hypertrophy in experimental renal failure. Some of this effect may be related to the attenuation of hypertension, but a direct effect on cardiac myocyte ROS production and growth was also identified. Clinical studies of green tea extract in chronic renal failure patients may be warranted.
PMID: 12675854 [PubMed - as supplied by publisher]
Toxicol Lett 2003 Apr 11;140-141:125-32 Related Articles, Links
Defenses against peroxynitrite: selenocompounds and flavonoids.
Klotz LO, Sies H.
Institut fur Physiologische Chemie I, Heinrich-Heine-Universitat Dusseldorf, Postfach 101007, D-40001, Dusseldorf, Germany
The inflammatory mediator peroxynitrite, when generated in excess, may damage cells by oxidizing and nitrating cellular components. Defense against this reactive species may be at the level of prevention of the formation of peroxynitrite, at the level of interception, or at the level of repair of damage caused by peroxynitrite. Several selenocompounds serve this purpose and include selenoproteins such as glutathione peroxidase (GPx), selenoprotein P and thioredoxin reductase, or low-molecular-weight substances such as ebselen. Further, flavonoids, such as (-)-epicatechin, which occurs in green tea or cocoa as monomer or in the form of oligomers, can contribute to cellular defense against peroxynitrite.
PMID: 12676458 [PubMed - in process]
Phytother Res 2003 Mar;17(3):206-9 Related Articles, Links
Protective effect of green tea polyphenol (-)-epigallocatechin gallate and other antioxidants on lipid peroxidation in gerbil brain homogenates.
Lee SR, Im KJ, Suh SI, Jung JG.
Department of Pharmacology, School of Medicine and Brain Research Institute, Keimyung University, Taegu, South Korea.
The aim of this study was to compare the protective effects of green tea polyphenol (-)-epigallocatechin gallate (EGCG) and other well-known antioxidants on the lipid peroxidation in gerbil brain homogenates. Oxidative stress was induced by H(2)O(2) (10 mM) or ferrous ammonium sulfate (5 micro M) and lipid peroxidation was studied. Hydrogen peroxide and ferrous ions are capable of oxidizing a wide range of substrates and causing biological damage. The reaction, referred to as the Fenton process, is complex and can generate both hydroxyl radicals and higher oxidation states of the iron. Thiobarbituric acid-reactive substances (TBA-RS) were used as a marker of lipid peroxidation. EGCG, trolox, lipoic acid, and melatonin reduced H(2)O(2)- or ferrous ion-induced lipid peroxidation in a concentration-dependant manner. In reducing the H(2)O(2)-induced lipid peroxidation, IC(50) values of antioxidants were as follows: EGCG (0.66 micro M), trolox (37.08 micro M), lipoic acid (7.88 mM), and melatonin (19.11 mM). In reducing the ferrous ion-induced lipid peroxidation, IC50 values of antioxidants were as follows: EGCG (3.32 micro M), trolox (75.65 micro M), lipoic acid (7.63 mM), and melatonin (15.48 mM). Under the in vitro conditions of this experiment, EGCG was the most potent antioxidant in inhibiting H(2)O(2) or ferrous ion-induced lipid peroxidation in the gerbil brain homogenates. Copyright 2003 John Wiley & Sons, Ltd.
PMID: 12672147 [PubMed - in process]
J Environ Biol 2002 Oct;23(4):373-6 Related Articles, Links
An anticlastogenic in vivo micronucleus assay for tea.
Edwin D, Geetha VR, Vishwanathan H, Usha Rani MV.
Department of Environmental Sciences, Bharathiar University, Coimbatore-641 046, Tamil Nadu, India.
[email protected]
Common use of antimutagens and anticarcinogens in everyday life is an effective measure for preventing human cancer and genetic diseases. Antioxidant properties of tea have vast potential as protective agents against diverse toxic effects. The present study was aimed to evaluate the role of aqueous clonal tea extracts (green tea, oolong tea and black tea) in modulating the genotoxic damage induced by cyclophosphamide (CP), a commonly used chemotherapeutic drug and a well-known mutagen and clastogen. All the three tea extracts at 1 and 2% concentration did not increase the frequency of micronucleated polychromatic erythrocytes (MPE) in bone marrow cells of mice when administered individually. The tea extracts decreased the micronuclei (MN) induced by CP. Therefore, regular intake of tea may improve the antioxidant status in in vivo and thereby reduce the risk of cancer and coronary heart disease.
PMID: 12674376 [PubMed - in process]
Food Chem Toxicol 2002 Jul;40(7):925-33
Inhibition of aromatase activity by green tea extract catechins and their endocrinological effects of oral administration in rats.
Satoh K, Sakamoto Y, Ogata A, Nagai F, Mikuriya H, Numazawa M, Yamada K, Aoki N.
We orally administered polyphenone-60 (P-60), green tea extract catechins, in the diet (0, 1.25 and 5%) to male rats for 2, 4 and 8 weeks initiated at 5 weeks old. It was found that a 5% dose to male rats for 2-8 weeks induced goiters and decreased weights of the body, testis and prostate gland. Endocrinologically, elevating plasma thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels and decreasing tri-iodothyronine (T(3)) and thyroxine (T(4)) levels were induced by this treatment. We also found that P-60 as a whole and some of its constituents exhibited inhibitory effects on human placental aromatase activity by in vitro assay. The concentration of P-60 that required producing 50% inhibition of the aromatase activity (IC(50) value) was 28 microg/ml. The IC(50) values of (-)-catechin gallate (Cg), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (-)-gallocatechin gallate (GCg) were 5.5 x 10(-6), 1.0 x 10(-4), 6.0 x 10(-5) and 1.5 x 10(-5) M, respectively. (-)- Epicatechin gallate (ECg) at 1.0 x 10(-4) M produced 20% inhibition. (-)-Epicatechin (EC) and (+)-catechin (CT) exhibited no effects on aromatase activity. The endocrinological changes observed in vivo were in conformity with antithyroid effects and aromatase inhibition effects of P-60 and its constituents.
freshen breath too
In the first study, conducted at Pace University, green tea extracts were mixed with several different kinds of bacteria, including those that cause strep throat and tooth decay. The researchers found that green tea was effective at fighting bacteria by inhibiting their growth.
"Our research shows tea extracts can destroy the organism that causes disease," says lead researcher Milton Schiffenbauer, PhD, a microbiologist and biology professor at Pace University in New York City, in a news release.
In fact, the same study suggests that green tea boosts the effectiveness of toothpaste and mouthwash in fighting viruses. Toothpaste and mouthwash had very little virus-fighting effect when mixed with bacteria; however, when green tea extract was added, 99% to 100% of the bacteria disappeared.
What's responsible for the health benefits of tea? Teas contain polyphenols, which are antioxidants that protect human cells from damage. Flavonids are a group of polyphenols that occur naturally in tea. It is suspected that high levels of these polyphenols in the body can fight viruses as well as cancer, including pancreas, colon, bladder, prostate, and breast cancer.
In the "bad breath" study, researchers combined black tea extracts with three species of bacteria (all linked with bad breath) in petri dishes for 48 hours. They compared the results with bacteria that sat alone.
In all cases, tea polyphenols inhibited the growth of bacteria by 30% and reduced the production of compounds that cause bad breath.
The study suggests that rinsing with black tea keeps plaque from forming and destroys acids that cause tooth decay.
"Besides inhibiting the growth of pathogens in the mouth, black tea and its polyphenols may benefit human oral health by suppressing the bad-smelling compounds that these pathogens produce," says lead researcher Christine D. Wu, PhD, professor of periodontics at the University of Illinois, Chicago, in a news release.
Both studies detailing health benefits of tea were presented at the annual American Society for Microbiology General Meeting held in Washington, D.C., this week.
Medical College of Georgia
**broken link removed**
Green Tea Linked to Skin Cell Rejuvenation
Christine Hurley Deriso
Research into the health-promoting properties of green tea is yielding
information that may lead to new treatments for skin diseases and
wounds.
Dr. Stephen Hsu, a cell biologist in the Medical College of Georgia
Department of Oral Biology, has uncovered a wealth of information
about green tea in the last few years. Most importantly, he helped
determine that compounds in green tea called polyphenols help
eliminate free radicals, which can cause cancer by altering DNA. He
also found that polyphenols safeguard healthy cells while ushering
cancer cells to their death.
He recently began studying the most abundant green tea polyphenol,
EGCG. Using pooled human keratinocytes (skin cells), he and his
colleagues studied the normal growth of the skin cells and compared it
to the growth of the cells when exposed to EGCG.
To their astonishment, they found that EGCG reactivated dying skin
cells. "Cells that migrate toward the surface of the skin normally
live about 28 days, and by day 20, they basically sit on the upper
layer of the skin getting ready to die," Dr. Hsu said. "But EGCG
reactivates them. I was so surprised."
The skin consists of three layers: the epidermis (outer layer), dermis
(mid-layer) and hypodermis (inner layer). Dr. Hsu learned that green
tea polyphenols aren’t absorbed beyond the epidermis, so any benefits
are limited to that outer layer of skin. But the benefits, he
stressed, seem significant.
Cells in the epidermis, or keratinocytes, are in a constant state of
renewal. The newly formed cells, stem cells, are undifferentiated but
rapidly dividing. As they push through the epidermis, they begin
differentiating. During this migration and differentiation process,
the cells are very active, expending and consuming vast amounts of
energy.
Once they reach the surface of the skin, their metabolic activity
slows dramatically and they prepare to die, while forming a
water-proof, sheet-like structure. As they die off about a month into
their life cycle, they are replaced by another wave of migrating cells
supplied by stem cells, starting the process all over again.
But EGCG seems to be a fountain of youth for skin cells. "When exposed
to EGCG, the old cells found in the upper layers of the epidermis
appear to start dividing again," Dr. Hsu said. "They make DNA and
produce more energy. They are reactivated. There are lots of
unknowns--this is the first step into the door--but if we can energize
dying skin cells, we can probably improve the skin condition."
In addition, the researchers found that EGCG accelerates the
differentiation process among new cells.
Combining these effects of EGCG on skin cells in different layers of
the epidermis, Dr. Hsu noted potential benefits for skin conditions as
diverse as aphthous ulcers, psoriasis, rosascea, wrinkles and wounds.
"If skin cells surrounding wounds or infections don’t heal in time,
fibroblasts in the connective tissue may rush in to fill the void and
cause scar tissue formation," he said. "If we can spur the skin cells
to differentiate and proliferate, we can potentially accelerate the
wound-healing process and prevent scarring."
This potential benefit is particularly exciting for conditions such as
diabetes, which stubbornly inhibits the wound-healing process, Dr. Hsu
said.
He and his colleagues hope to identify dermatologists interested in
collaborating on clinical studies of EGCG and other polyphenols on
patients.
Dr. Hsu’s research, which is excerpted on the online version of the
Journal of Pharmacology and Experimental Therapeutics, is funded by
the Dental Research Foundation, the MCG School of Dentistry and MCG
Research Institute.
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Plus the brew is dirt cheap and the link I provided is very very yummy 
