Green Tea???'s

wojo

wojo

Well-known member
ok whats a good amount daily of egcg's? egcgs are catechins..right? what are polyphenols..now makesa a green tea extract pretty cheap and i am intrigued by this substance but as u can tell im in the dark here...i read about it on animalboard but thats like being a blindman looking for a cat in a dark thats not even there sometimes..can someone just point me in the right direction please
 
fine dont wanna aanswer i did my own research..so nana
here ya go..some very cool things about green tea

Curr Med Chem Anti-Canc Agents 2002 Jul;2(4):441-63 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]

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Drug News Perspect 2002 Sep;15(7):432-438 Links


Are Catechins Natural Tyrosine Kinase Inhibitors?

Sachinidis A, Hescheler J.

Enhanced activity of tyrosine kinase receptors (RTKs) has been implicated as a contributing factor in the development of malignant and nonmalignant proliferative diseases such as cancer and atherosclerosis. Several growth factors traducing mitogenic signals through RTKs are implicated in the development of tumor and cardiovascular diseases. Therefore, in recent years many efforts have been made to develop RTK small molecule inhibitors for the treatment of tumor and cardiovascular diseases. Recently, catechins, the main compounds of green tea leafs, have been identified as potent natural inhibitors of several RTKs. Furthermore, there is increasing evidence that catechins possess antiangiogenic properties. In summary, several animal and cell culture studies suggest that catechins are potential candidates for the clinical therapy of cancer and cardiovascular diseases. (c) 2002 Prous Science. All rights reserved.

PMID: 12677178 [PubMed - as supplied by publisher]


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.

Effects of green tea polyphenols on dopamine uptake and on MPP+ -induced dopamine neuron injury.

Pan T, Fei J, Zhou X, Jankovic J, Le W.

Department of Neurology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.

As antioxidants, polyphenols are considered to be potentially useful in preventing chronic diseases in man, including Parkinson's disease (PD), a disease involving dopamine (DA) neurons. Our studies have demonstrated that polyphenols extracted from green tea (GT) can inhibit the uptake of 3H-dopamine (3H-DA) and 1-methyl-4-phenylpyridinium (MPP(+)) by DA transporters (DAT) and partially protect embryonic rat mesencephalic dopaminergic (DAergic) neurons from MPP(+)-induced injury. The inhibitory effects of GT polyphenols on 3H-DA uptake were determined in DAT-pCDNA3-transfected Chinese Hamster Ovary (DAT-CHO) cells and in striatal synaptosomes of C57BL/6 mice in vitro and in vivo. The inhibitory effects on 3H-MPP(+) uptake were determined in primary cultures of embryonic rat mesencephalic DAergic cells. Inhibition of uptake for both 3H-DA and 3H-MPP(+) was dose-dependent in the presence of polyphenols. Incubation with 50 microM MPP(+) resulted in a significant loss of tyrosine-hydroxylase (TH)-positive cells in the primary embryonic mesencephalic cultures, while pretreatment with polyphenols (10 to 30 microg/ml) or mazindol (10 microM), a classical DAT inhibitor, significantly attenuated MPP(+)-induced loss of TH-positive cells. These results suggest that GT polyphenols have inhibitory effects on DAT, through which they block MPP(+) uptake and protect DAergic neurons against MPP(+)-induced injury.

PMID: 12495785 [PubMed - indexed for MEDLINE]
 
Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity.

Dulloo AG, Seydoux J, Girardier L, Chantre P, Vandermander J.

Institute of Physiology, University of Fribourg, Fribourg, Switzerland. [email protected]

The thermogenic effect of tea is generally attributed to its caffeine content. We report here that a green tea extract stimulates brown adipose tissue thermogenesis to an extent which is much greater than can be attributed to its caffeine content per se, and that its thermogenic properties could reside primarily in an interaction between its high content in catechin-polyphenols and caffeine with sympathetically released noradrenaline (NA). Since catechin-polyphenols are known to be capable of inhibiting catechol-O-methyl-transferase (the enzyme that degrades NA), and caffeine to inhibit trancellular phosphodiesterases (enzymes that break down NA-induced cAMP), it is proposed that the green tea extract, via its catechin-polyphenols and caffeine, is effective in stimulating thermogenesis by relieving inhibition at different control points along the NA-cAMP axis. Such a synergistic interaction between catechin-polyphenols and caffeine to augment and prolong sympathetic stimulation of thermogenesis could be of value in assisting the management of obesity. International Journal of Obesity (2000) 24, 252-258

PMID: 10702779 [PubMed - indexed for MEDLINE]

Am J Clin Nutr 1999 Dec;70(6):1040-5 Links


Comment in:
Am J Clin Nutr. 2000 Nov;72(5):1232-4.

Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.

Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J.

Department of Physiology, Faculty of Medicine, University of Geneva. [email protected]

BACKGROUND: Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system. OBJECTIVE: We investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-h energy expenditure (EE) and fat oxidation in humans. DESIGN: Twenty-four-hour EE, the respiratory quotient (RQ), and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men. On 3 separate occasions, subjects were randomly assigned among 3 treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner. RESULTS: Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%; P < 0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P < 0.001) without any change in urinary nitrogen. Twenty-four-hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo (40%, P < 0.05). Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines. CONCLUSIONS: Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.


full article Invalid Link Removed
 
pretty good article

Invalid Link RemovedDescription and Constituents

Tea is one of the most widely consumed beverages in the world today, second only to water, and its medicinal properties have been widely explored. The tea plant, Camellia sinensis, is a member of the Theaceae family, and black, oolong, and green tea are produced from its leaves. It is an evergreen shrub or tree and can grow to heights of 30 feet, but is usually pruned to 2-5 feet for cultivation. The leaves are dark green, alternate and oval, with serrated edges, and the blossoms are white, fragrant, and appear in clusters or singly. Unlike black and oolong tea, green tea production does not involve oxidation of young tea leaves. Green tea is produced from steaming fresh leaves at high temperatures, thereby inactivating the oxidizing enzymes and leaving the polyphenol content intact. The polyphenols found in tea are more commonly known as flavanols or catechins and comprise 30-40 percent of the extractable solids of dried green tea leaves. The main catechins in green tea are epicatechin, epicatechin-3-gallate, epigallocatechin, and epigallocatechin-3-gallate (EGCG), with the latter being the highest in concentration. Green tea polyphenols have demonstrated significant antioxidant, anticarcinogenic, anti-inflammatory, thermogenic, probiotic, and antimicrobial properties in numerous human, animal, and in vitro studies.1,2



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Mechanisms of Action

The anticarcinogenic properties of green tea polyphenols, mainly EGCG, are likely a result of inhibition of biochemical markers of tumor initiation and promotion, induction of apoptosis, and inhibition of cell replication rates, thus retarding the growth and development of neoplasms.3,4 Their antioxidant potential is directly related to the combination of aromatic rings and hydroxyl groups that make up their structure, and is a result of binding and neutralization of free radicals by the hydroxyl groups. In addition, green tea polyphenols stimulate the activity of hepatic detoxification enzymes, thereby promoting detoxification of xenobiotic compounds, and are also capable of chelating metal ions, such as iron, that can generate radical oxygen species.5,6

Green tea polyphenols inhibit the production of arachidonic acid metabolites such as pro-inflammatory prostaglandins and leukotrienes, resulting in a decreased inflammatory response. Human and animal studies have demonstrated EGCG's ability to block inflammatory responses to ultraviolet A and B radiation as well as significantly inhibiting the neutrophil migration that occurs during the inflammatory process.7-9

Research on green tea's thermogenic properties indicates a synergistic interaction between its caffeine content and catechin polyphenols may result in prolonged stimulation of thermogenesis. Studies have also shown green tea extracts are capable of reducing fat digestion by inhibiting digestive enzymes.10,11 Although the exact mechanism is unknown, green tea catechins have been shown to significantly raise levels of Lactobacilli and Bifidobacteria while decreasing levels of numerous potential pathogens.12 Studies have also demonstrated green tea's antibacterial properties against a variety of gram-positive and gram-negative species.13



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Clinical Indications

Cancer Prevention/Inhibition: Several studies have demonstrated green tea polyphenols' preventative and inhibitory effects against tumor formation and growth. While the studies are not conclusive, green tea polyphenols, particularly EGCG, may be effective in preventing cancer of the prostate, breast, esophagus, stomach, pancreas, and colon.14 There is also some evidence that green tea polyphenols may be chemopreventative or inhibitory toward lung, skin, and liver cancer,15-17 bladder and ovarian tumors,18,19 leukemia,20 and oral leukoplakia.21

Antioxidant Applications: Many chronic disease states and inflammatory conditions are a result of oxidative stress and subsequent generation of free radicals. Some of these include heart disease (resulting from LDL oxidation), renal disease and failure, several types of cancer, skin exposure damage caused by ultraviolet (A and B) rays, as well as diseases associated with aging. Green tea polyphenols are potent free radical scavengers due to the hydroxyl groups in their chemical structure. The hydroxyl groups can form complexes with free radicals and neutralize them, preventing the progression of the disease process.22

Obesity/Weight Control: Recent studies on green tea's thermogenic properties have demonstrated a synergistic interaction between caffeine and catechin polyphenols that appears to prolong sympathetic stimulation of thermogenesis. A human study of green tea extract containing 90 mg EGCG taken three times daily concluded that men taking the extract burned 266 more calories per day than did those in the placebo group and that green tea extract's thermogenic effects may play a role in controlling obesity.23 Green tea polyphenols have also beeen shown to markedly inhibit digestive lipases in vitro, resulting in decreased lipolysis of triglycerides, which may translate to reduced fat digestion in humans.10,11

Intestinal Dysbiosis and Infection: A small study in Japan demonstrated a special green tea catechin preparation (30.5% EGCG) was able to positively affect intestinal dysbiosis in nursing home patients by raising levels of Lactobacilli and Bifidobacteria while lowering levels of Enterobacteriaceae, Bacteroidaceae, and eubacteria. Levels of pathogenic bacterial metabolites were also decreased.12 An in vitro study also demonstrated green tea's antimicrobial activity against a variety of gram-positive and gram-negative pathogenic bacteria that cause cystitis, pyelonephritis, diarrhea, dental caries,24 pneumonia, and skin infections.13

Other Applications: Sickle cell anemia is characterized by a population of "dense cells" that may trigger vaso-occlusion and the painful sickle cell "crisis." One study demonstrated that 0.13 mg/mL green tea extract was capable of inhibiting dense-cell formation by 50 percent.25

Another potential therapeutic application of green tea is the treatment of psoriasis. The combination therapy of psoralens and ultraviolet A radiation is highly effective but has unfortunately been shown to substantially increase the risk for developing squamous cell carcinoma and melanoma. An in vitro study using human and mouse skin demonstrated that pre- and post-treatment with green tea extract inhibited DNA damage induced by the psoralen/ultraviolet A radiation exposure.8



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Dosage and Toxicity

Green tea is generally considered a safe, non-toxic beverage and consumption is usually without side-effects. The average cup of green tea, however, contains from 10-50 mg of caffeine and overconsumption may cause irritability, insomnia, nervousness, and tachycardia. Because studies on its possible teratogenic effect are inconclusive, caffeine consumption is contraindicated during pregnancy. Lactating women should also limit caffeine intake to avoid sleep disorders in infants.26

The dosage for green tea beverage varies, depending on the clinical situation and desired therapeutic effect. The phenolic content of green tea infusion is between 50-100 mg polyphenols per cup, depending on species, harvesting variables, and brewing methods,27 with typical dosages ranging from 3 to 10 cups per day. Cancer preventative effects are usually associated with dosages in the higher end of the range.28 Green tea extracts standardized to 80-percent total polyphenols are dosed at an average of 500-1500 mg per day.
 
nice!! now I have proof that it will inhibit lipid peroxidation in my gerbil brain! j/k bro, this is a solid string of info... man, we *gotta* take the time to write some damn articles of our own :D
 
sorry it was tough enough at 3 am reading through all the pubmed studies..lol..
 
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