Browsing by Subject "Tea"

Now showing 1 - 3 of 3
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    Effects of folate cycle disruption by the green tea polyphenol epigallocatechin-3-gallate
    (PERGAMON-ELSEVIER SCIENCE LTD, 2007) Navarro Perán, Encarnación María; Cabezas Herrera, Juan; Rodríguez López, José Neptuno; Sánchez del Campo Ferrer, Luis; Bioquímica y Biología Molecular A
    We demonstrate that the tea polyphenol, epigallocatechin-3-gallate, is an efficient inhibitor of human dihydrofolate reductase. Like other antifolate compounds, epigallocatechin-3-gallate acts by disturbing folic acid metabolism in cells, causing the inhibition of DNA and RNA synthesis and altering DNA methylation. Epigallocatechin-3-gallate was seen to inhibit the growth of a human colon carcinoma cell line in a concentration and time dependent manner. Rescue experiments using leucovorin and hypoxanthine-thymine medium were the first indication that epigallocatechin-3-gallate could disturb the folate metabolism within cells. Epigallocatechin-3-gallate increased the uptake of [H-3]-thymidine and showed synergy with 5-fluorouracil, while its inhibitory action was strengthened after treatment with hypoxanthine, which indicates that epigallocatechin-3-gallate decreases the cellular production of nucleotides, thus, disturbing DNA and RNA synthesis. In, addition to its effects on nucleotide biosynthesis, antifolate treatment has been linked to a decrease in cellular methylation. Here, we observed that epigallocatechin-3-gallate altered the p16 methylation pattern from methylated to unmethylated as a result of folic acid deprivation. Finally, we demonstrate that epigallocatechin-3-gallate causes adenosine to be released from the cells because it disrupts the purine metabolism. By binding to its specific receptors, adenosine can modulate different signalling pathways. This proposed mechanism should help us to understand most of the molecular and cellular effects described for this tea polyphenol
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    Synthesis and Biological Activity of a 3,4,5-Trimethoxybenzoyl Ester Analogue of Epicatechin-3-gallate
    (AMER CHEMICAL SOC, 2008-04-10) Otón Vidal, Francisco; Tárraga Tomás, Alberto; Cabezas Herrera, Juan; Chazarra Parres, Soledad; Rodríguez López, José Neptuno; Sánchez del Campo Ferrer, Luis; Bioquímica y Biología Molecular A
    Despite presenting bioavailability problems, tea catechins have emerged as promising chemopreventive agents because of their observed efficacy in various animal models. To improve the stability and cellular absorption of tea polyphenols, we developed a new catechin-derived compound, 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG), which has shown significant antiproliferative activity against several cancer cell lines, especially melanoma. The presence of methoxy groups in its ester-bound gaily] moiety drastically decreased its antioxidant and prooxidant properties without affecting its cell-antiproliferative effects, and the data indicated that the 3-gallyl moiety was essential for its biological activity. As regards its action mechanism, we demonstrated that TMECG binds efficiently to human dihydrofolate reductase and down-regulates folate cycle gene expression in melanoma cells. Disruption of the folate cycle by TMECG is a plausible explanation for its observed biological effects and suggests that, like other antifolate compounds, TMECG could be of clinical value in cancer therapy.
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    Tea polyphenols, their biological effects and potential molecular targets
    (Murcia : F. Hernández, 2008) Chen, Di; Milacic, Vesna; Si Chen, Marina; Biao Wan, Sheng; Har Lam, Wai; Huo, Congde; Landis-Piwowar, Kristin R.; Cindy Cui, Qiuzhi; Wali, Anil; Hang Chan, Tak; Ping Dou, Q.
    Tea is the most popular beverage in the world, second only to water. Tea contains an infusion of the leaves from the Camellia sinensis plant rich in polyphenolic compounds known as catechins, the most abundant of which is (-)-EGCG. Although tea has been consumed for centuries, it has only recently been studied extensively as a health-promoting beverage that may act to prevent a number of chronic diseases and cancers. The results of several investigations indicate that green tea consumption may be of modest benefit in reducing the plasma concentration of cholesterol and preventing atherosclerosis. Additionally, the cancer-preventive effects of green tea are widely supported by results from epidemiological, cell culture, animal and clinical studies. In vitro cell culture studies show that tea polyphenols potently induce apoptotic cell death and cell cycle arrest in tumor cells but not in their normal cell counterparts. Green tea polyphenols were shown to affect several biological pathways, including growth factor-mediated pathway, the mitogen-activated protein (MAP) kinasedependent pathway, and ubiquitin/proteasome degradation pathways. Various animal studies have revealed that treatment with green tea inhibits tumor incidence and multiplicity in different organ sites such as skin, lung, liver, stomach, mammary gland and colon. Recently, phase I and II clinical trials have been conducted to explore the anticancer effects of green tea in humans. A major challenge of cancer prevention is to integrate new molecular findings into clinical practice. Therefore, identification of more molecular targets and biomarkers for tea polyphenols is essential for improving the design of green tea trials and will greatly assist in a better understanding of the mechanisms underlying its anti-cancer activity.