MEDC 533 - Green Tea

TITLE Ryan Albert, Allyson Angles, Ann Bui, Michael Dail, Laura Hunter Ford, Ruta Patel, William Wolanski Class of 2013, School of Pharmacy, Virginia Commonwealth University ABSTRACT INTRODUCTION INTRODUCTION (cont’d) CONCLUSION LITERATURE CITED PHARMACOLOGY Green tea (Camellia sinensis) is traditionally consumed as a beverage. It exhibits strong antioxidant activity and is used primarily for its perceived anticancer, cardio-protective, and calming effects, although clinical studies are lacking. C. sinensis is a large shrub with evergreen leaves native to eastern Asia, where it is cultivated extensively. Tea leaves contain varying amounts of polyphenols, which are classified as catechins. The major polyphenol in green tea, as well as the most studied, is (-)-epigallocatechin gallate (EGCG) with lesser amounts of catechin, epicatechin, gallocatechin, gallocatechin gallate, and epicatechin gallate. The leaves also possess smaller quantities of caffeine, theobromine, theophylline, theanine, and phenolic acids. Side effects related to the use of green tea are limited to date, although insomnia has been reported. Green tea contains approximately 30-60mg of caffeine for every 6-8 ounces and is the likely cause for insomnia. The amount of caffeine present in green tea is much less when compared to the amount of caffeine in coffee (approximately 100mg per 8 ounces). Also, green tea has been shown to interfere in one patient on Warfarin therapy, due to the presence of Vitamin K. ACKNOWLEDGEMENTS Green Tea catechins provide cardiovascular benefits through their antioxidant properties by inhibiting LDL oxidation, reducing TBARS formation, cellular oxidation and superoxide production, and inhibiting smooth muscle cells proliferation. Green tea catechins have been shown to prolong lag time, inhibit formation of oxidized cholesterol and decrease lioleic acid and arachdonic acid concentrations. Proliferation of vascular smooth muscle cells stimulated with advanced glycation end products or native LDL was dose-dependent inhibited by green tea polyphenols. The healthful properties of green tea are attributed to polyphenols because of their potent antioxidant properties, which appear to be greater than that of Vitamin C. Alkaloids present in green tea, such as caffeine, theobromine, and theophylline, provide for its’ stimulant effects. The Federal Trade Commission controls the advertising of green tea. In order for a claim to be made for green tea, claims must be identified and these claims must be assessed based on evidence on the product. PHARMACOKINETICS and PHARMACODYNAMICS Ingestion of green tea results in a peak plasma concentration of 1.3 μmol of (-)-epigallocatchin gallate within 2 to 4 hours. Average peak plasma concentrations after a single dose of 1.5 mmol was highest for epigallocatechin (EGC) at 5 μmol and 3.1 μmol for epicatechin gallate; therefore, EGCG shows the lowest bioavailability. There is a difference in the bioavailability of different green tea catechins, and it is also influenced by dosing schedule. It was shown in one study that the AUC and Cmax was greatest following an 800mg IV bolus dose compared to a 400mg BID dose. http://commons.wikimedia.org/wiki/File:Green_tea_leaves.jpg Epidemiological studies and in vitro experiments demonstrate that tea consumption is inversely associated with cardiovascular disease, although a direct cause-effect relationship has not been conclusively demonstrated. One meta-analysis suggests that regular intake of tea might reduce the incidence of myocardial infarction and have other cardio-protective effects. However, the studies included in the analysis were too heterogeneous to allow for meaningful interpretation. RESULTS and DISCUSSION There are two major mechanisms that describe the role of green tea and the lowering of plasma cholesterol levels, both of which indicate that green tea play a role in the metabolism and handing of cholesterol once consumed. The first mechanism highlights an intracellular approach in which green tea affects plasma cholesterol levels. By decreasing cellular concentrations of cholesterol, more is absorbed by the hepatocytes and metabolized versus being available to circulate in the plasma. In a study performed in hepatocytes, green tea decreased the cell cholesterol concentration (-30%) and increased the conversion of the sterol-regulated element binding protein (SREBP-1) from the inactive precursor form to the active transcription-factor form. Consistent with this, the mRNA of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis, was also increased by green tea. PHARMACOKINETICS and PHARMACODYNAMICS (cont’d) Mechanisms of action under investigation include reduced low density lipoprotein oxidation, enhanced endothelial cell functioning, effects on atherosclerosis, hypotensive effects, platelet aggregation, and improved cholesterol profiles. Green tea caused up-regulation of the LDL receptor in HepG2 cells. The effect was most likely mediated through SREBP-1 in response to a decrease in the intracellular cholesterol concentration. The authors of this poster would like to acknowledge Virginia Commonwealth University School of Pharmacy, Dr. Yan Zhang from VCU Department of Medicinal Chemistry, Dr. Lisa Phipps from VCU School of Pharmacy … ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],PICTURE

MEDC 533 - Green Tea

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MEDC 533 - Green Tea