cancer-prevention

Author: Orly Weinreb and Silvia Mandel and Tamar Amit and Moussa B.H. Youdim

Tea consumption is varying its status from a mere ancient beverage and a lifestyle habit, to a nutrient endowed with possible prospective neurobiological–pharmacological actions beneficial to human health. Accumulating evidence suggest that oxidative stress resulting in reactive oxygen species generation and inflammation play a pivotal role in neurodegenerative diseases, supporting the implementation of radical scavengers, transition metal (e.g., iron and copper) chelators, and nonvitamin natural antioxidant polyphenols in the clinic. These observations are in line with the current view that polyphenolic dietary supplementation may have an impact on cognitive deficits in individuals of advanced age. As a consequence, green tea polyphenols are now being considered as therapeutic agents in well controlled epidemiological studies, aimed to alter brain aging processes and to serve as possible neuroprotective agents in progressive neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. In particular, literature on the putative novel neuroprotective mechanism of the major green tea polyphenol, (−)-epigallocatechin-3-gallate, are examined and discussed in this review.

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Author: Michael Xavier Doss and Shiva Prasad Potta and Jürgen Hescheler and Agapios Sachinidis

The prevention of cancer through dietary intervention is currently receiving considerable attention. Several epidemiological studies substantiate that green tea has a protective effect against a variety of malignant proliferative disorders such as lung cancer, breast cancer and prostate cancer. This preventive potential of green tea against cancer is attributed to the biologically active flavonoids called catechins. Epigallocatechin 3-o-gallate, the major catechin found in green tea, mediates diverse physiological and pharmacological actions in bringing about the regression of the tumors and also lowers the risk of nonmalignant cardiovascular proliferative diseases. Much of the current research is being focused on how these catechins specifically bring about the regression of the experimentally induced tumors both in vitro and in vivo. These catechins exert diverse physiological effects against proliferative diseases by several mechanisms, most of which are not completely characterized. This review summarizes the mechanisms by which these catechins play an essential role in regulating the process of carcinogenesis, with a special emphasis on how these catechins antagonize the growth factor-induced proliferative disorders.

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Author: A.M. van Nederkassel and M. Daszykowski and D.L. Massart and Y. Vander Heyden

In this paper, a fast strategy for determining the total antioxidant capacity of Chinese green tea extracts is developed. This strategy includes the use of experimental techniques, such as fast high-performance liquid chromatography (HPLC) on monolithic columns and a spectrophotometric approach to determine the total antioxidant capacity of the extracts. To extract the chemically relevant information from the obtained data, chemometrical approaches are used. Among them there are correlation optimized warping (COW) to align the chromatograms, robust principal component analysis (robust PCA) to detect outliers, and partial least squares (PLS) and uninformative variable elimination partial least squares (UVE-PLS) to construct a reliable multivariate regression model to predict the total antioxidant capacity from the fast chromatograms.

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Author: Woochang Lee and Won-Ki Min and Sail Chun and Yong-Wha Lee and Hyosoon Park and Do Hoon Lee and You Kyoung Lee and Ji Eun Son

Objectives: Smoking is a risk factor for coronary artery disease and triggers vascular injury by platelet aggregation and induces atherosclerosis through induction of oxidative stress. Green tea is known to have antioxidant capacity and anti-platelet activity. Design and methods: Twenty adult male smokers ingested 600 mL of green tea for 4 weeks. Their lipid profile, C-reactive protein (CRP), total antioxidant capacity, oxidized LDL, soluble VCAM-1, soluble ICAM-1, and soluble P-selectin were measured at baseline and 2 and 4 weeks after green tea ingestion. Results: Plasma soluble P-selectin (sP-selectin) levels decreased significantly after 2 and 4 weeks of green tea ingestion compared with those before green tea ingestion (P < 0.001). Plasma concentrations of oxidized LDL decreased significantly after green tea ingestion (P < 0.05). Conclusions:The results of this study suggest the effect of green tea on sP-selectin and oxidized LDL.

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Author: Bo Zhou and Long-Min Wu and Li Yang and Zhong-Li Liu

The synergistic antioxidant mechanism of α-tocopherol (vitamin E) with green tea polyphenols, i.e., (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin gallate (EGCG), and gallic acid (GA), was studied by assaying the kinetics of the reaction of α-tocopheroxyl radical with green tea polyphenols by stopped-flow electron paramagnetic resonance, the inhibition of linoleic acid peroxidation by these antioxidants, and the decay of α-tocopherol during the peroxidation. It was found that the green tea polyphenols could reduce α-tocopheroxyl radical to regenerate α-tocopherol with rate constants of 0.45, 1.11, 1.31, 1.91, and 0.43 × 102 M−1 s−1 for EC, EGC, ECG, EGCG, and GA, respectively, in sodium dodecyl sulfate micelles. In addition, these second-order rate constants exhibited a good linear correlation with their oxidation potentials, suggesting that electron transfer might play a role in the reaction.

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Author: Sibel Tas and Emre Sarandol and Sedef Ziyanok and Kemal Aslan and Melahat Dirican

In recent years, green tea has become a subject of interest because of its beneficial effects on human health. The purpose of this study was to determine the effects of green tea on serum paraoxonase/arylesterase activities and lipoprotein oxidizability in streptozotocin-induced diabetic rats (65 mg/kg [intraperitoneal]). Green tea was given in tap water (2%) for 3 and 6 weeks to control (CGT-3w and CGT-6w) and diabetic (DGT-3w and DGT-6w) rats, and they were compared with the control and diabetic groups (D-3w and D-6w), respectively. Serum insulin level was significantly increased in the DGT-6w group; serum lipid and plasma and tissue malondialdehyde levels were reduced in the DGT-3w and DGT-6w groups. Oxidizability of apolipoprotein B–containing lipoprotein fraction was found to be significantly reduced in the DGT-6w group. Serum total antioxidant capacity showed a significant increase in the CGT-6w and DGT-6w groups. Paraoxonase activity was significantly reduced in the D-3w and D-6w groups and increased in the DGT-6w group. We conclude that green tea might have antihyperlipidemic and antioxidative effects and may slow the progression of atherogenesis by reducing oxidation of lipoproteins and preserving paraoxonase activity.

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Author: Jeong-Sang Lee and Tae-Young Oh and Young-Kyung Kim and Joo-Hyun Baik and Sung So and Ki-Baik Hahm and Young-Joon Surh

There are multiple lines of compelling evidence from epidemiologic and laboratory studies supporting that frequent consumption of green tea is inversely associated with the risk of chronic human diseases including cancer. The chemopreventive and chemoprotective effects of green tea have been largely attributed to antioxidative and anti-inflammatory activities of its polyphenolic constituents, such as epigallocatechin gallate. The present study was designed to evaluate the efficacy of green tea polyphenols in protecting against alcohol-induced gastric damage and to elucidate the underlying mechanisms. Intragastric administration of ethanol to male Sprague–Dawley rats caused significant gastric mucosal damage, which was accompanied by elevated expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) as well as transient activation of redox-sensitive transcription factors, such as NF-κB and AP-1, and mitogen-activated protein kinases (MAPKs). Oral administration of the green tea polyphenolic extract (GTE) significantly ameliorated mucosal damages induced by ethanol and also attenuated the ethanol-induced expression of COX-2 and iNOS. Inactivation of MAPKs, especially p38 and ERKl/2, by GTE might be responsible for inhibition of ethanol-induced expression of COX-2 and iNOS.

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Author: Andrea Sapone and Donatella Canistro and Massimiliano Broccoli and Laura Pozzetti and Alessandra Affatato and Stefano Vangelisti and Gian Luigi Biagi and Valeriana Sblendorio and Moreno Paolini

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Author: Susanne M. Henning and Yantao Niu and Yong Liu and Nicolas H. Lee and Yukihiko Hara and Gail D. Thames and Rosario R. Minutti and Catherine L. Carpenter and Hejing Wang and David Heber

Tea polyphenols have strong in vitro antioxidant activity. Due to their limited bioavailability, however, their contribution to in vivo antioxidant activity may depend on the form of administration. A human intervention study was performed to evaluate the bioavailability and antioxidant capacity of (−)-epigallocatechin-3-gallate (EGCG) administered as a single large dose in the form of either purified EGCG or as green tea extract (Polyphenon E). Plasma concentrations of tea polyphenols were determined by high-performance liquid chromatography (HPLC) analysis combined with coulometric array electrochemical detection (ECD). We found no differences in plasma EGCG concentrations and trolox equivalents determined by the trolox equivalent antioxidant capacity assay after administration of either form of EGCG. However, we found that the plasma antioxidant activity was significantly affected by changes in the plasma urate concentration, which may have interfered with the effect of tea polyphenols on the antioxidant activity. In addition, lymphocyte 8-hydroxydeoxyguanosine to deoxyguanosine (8-OHdG/106dG) ratios were determined by HPLC with ECD. The 8-OHdG/106dG ratios did not change significantly during the 24 h following both EGCG interventions but correlated significantly within individuals determined during the two interventions separated by 1 week. In summary, changes in plasma uric acid due to dietary intake were significantly correlated to the plasma antioxidant activity and exerted a stronger influence on the plasma antioxidant activity compared with the EGCG intervention. In future studies of dietary effects on the plasma antioxidant capacity, changes in plasma uric acid will need to be closely monitored.

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Author: Han-Ki Park and Dong-Wook Han and Young Hwan Park and Jong-Chul Park

Green tea has shown remarkable anti-inflammatory and cancer chemopreventive effects in many animal tumor bioassays, cell culture systems and epidemiological studies. Many of these biological effects of green tea are mediated by epigallocatechin 3-gallate, the major polyphenol present therein. In this study, the differential biological responses of green tea polyphenols (GTP) were examined in normal rat osteoblasts (NRO) vs. human osteosarcoma (MG-63 and Saos-2) cells. The GTP treatment with micromolar concentrations (0.1, 1, 10 and 100 μM for 24 h) resulted in dose-dependent inhibitions of cell growth and alkaline phosphatase activity, morphological alterations, G0/G1-phase arrest of the cell cycle and induction of apoptosis in both osteosarcoma cells, but not in the NRO. These results suggest that the GTP treatment may be contributed to the differential regulation of cell cycle in normal cells and cancer cells, which can be exploited to craft strategies for the physiological preservation of cells or tissues by GTP.

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