Research Database

Author: M.S. Westerterp-Plantenga

The global prevalence of obesity has increased considerably in the last decade. Tools for obesity management including caffeine, and green tea have been proposed as strategies for weight loss and weight maintenance. These ingredients may increase energy expenditure and have been proposed to counteract the decrease in metabolic rate that is present during weight loss. Positive effects on body-weight management have been shown using green tea mixtures. Green tea, by containing both tea catechins and caffeine, may act through inhibition of catechol O-methyl-transferase, and inhibition of phosphodiesterase. Here the mechanisms may also operate synergistically. A green tea–caffeine mixture improves weight maintenance, through thermogenesis, fat oxidation, and sparing fat free mass. The sympathetic nervous system is involved in the regulation of lipolysis, and the sympathetic innervation of white adipose tissue may play an important role in the regulation of total body fat in general. Taken together, these functional ingredients have the potential to produce significant effects on metabolic targets such as thermogenesis, and fat oxidation. An ethnic or genetic effect, and habitual caffeine or green tea catechin intake may act as confounders; this remains to be revealed.

 

 

Get the whole article here

Author: Rashmi Singh and Nahid Akhtar and Tariq M. Haqqi

A number of factors including inflammation and oxidative stress are believed to play a role in the development of chronic joint diseases. Green tea has become a popular drink and is consumed throughout the world. Extracts of green tea and polyphenols present therein have been shown to inhibit the inflammatory responses in vitro in different cell types and the development of arthritis in animal model studies. There is considerable evidence that (−)-epigallocatechin-3-gallate (EGCG), the predominant green tea polyphenol which mimic its effects, inhibits enzyme activities and signal transduction pathways that play important roles in inflammation and joint destruction in arthritis. After oral consumption EGCG become bioavailable and proteomic studies suggest that EGCG may directly interact with a large set of protein targets and alter the physiological response of the cells. Taken together these and other studies identify and support the use of EGCG as a possible chemopreventive agent with a potential to inhibit the development of arthritis. Here we review the biological effects of EGCG in an attempt to understand its pivotal molecular targets that directly affect the inflammation and joint destruction process for prevention and/or for the development of new therapeutics for arthritis in humans.

 

 

Get the whole article here

Author: Jonathan M. Hodgson and Kevin D. Croft

The two main types of tea are green and black. Both green and black teas are rich dietary sources of flavonoids. Available evidence suggests that regular tea consumption may reduce the risk of cardiovascular disease. The cardiovascular health benefits of drinking tea are thought to be largely due to flavonoids. Tea intake and intake of flavonoids found in tea have been associated with reduced risk of cardiovascular disease in cross-sectional and prospective population studies. Isolated flavonoids found in tea have also been consistently shown to inhibit the development of atherosclerosis in animal models. A number of possible pathways and mechanisms have been investigated. There is now consistent data indicating that tea and tea flavonoids can enhance nitric oxide status and improve endothelial function, which may be at least partly responsible for benefits on cardiovascular health. There is also evidence, although limited, to suggest benefits of green tea (flavonoids) on body weight and body fatness. Data supporting reduced oxidative damage, inflammation, platelet activation, blood pressure, and risk of type 2 diabetes with tea (flavonoids) remains inadequate to draw any conclusions.

 

 

Get the whole article here

Author: Laurent Bazinet and Monica Araya-Farias and Alain Doyen and Dominique Trudel and Bernard Têtu

Due to the increasing market for functional foods and the chemopreventive action of (−)-epigallocatechin gallate (EGCG), manufacturers produce ready-to-drink green tea infusions enriched or not in EGCG. However, the maintenance of green tea catechins stability in drinks is always a challenge. In this context, the objectives of this study were (1) to assess the catechin stability in tea drink during a 6-month storage, (2) to evaluate the impact of process unit operations on catechin stability and (3) to compare the catechin and caffeine contents of commercially available tea drinks. It appeared that the stability of catechins during long-term storage was optimum at low temperature (4 °C) and acidic pH (pH 4.0). During the processing of the EGCG-enriched green tea drink, all the process unit operations, except heat-treatment, had no impact on catechin concentrations. In addition, in commercially available tea drinks, except enriched green tea drinks, their catechin contents are very low to provide health benefits.

 

 

Get the whole article here

Author: Hajime Fujii and Hiroshi Nishioka and Koji Wakame and Bernadene A. Magnuson and Ashley Roberts

Oligonol is a phenolic product derived from lychee fruit extract and green tea extract, containing catechin-type monomers and oligomers of proanthocyanidins, produced by a manufacturing process which converts polyphenol polymers into oligomers. The safety of Oligonol was assessed in acute and subchronic studies and genotoxicity assays. In a single dose acute study of Oligonol, male and female rats were administered 2000mg/kg body weight (bw) Oligonol in water by gavage. Oligonol caused no adverse effects and body weight gain and food consumption were within normal range, thus the LD(50) of Oligonol was determined to be greater than 2000mg/kg. A 90 day subchronic study (100, 300 and 1000mg/kgbw/day, oral gavage) in male and female rats reported no significant adverse effects in food consumption, body weight, mortality, clinical chemistry, haematology, gross pathology and histopathology. Similarly, no adverse effects were observed in mice fed diets providing 2, 20 or 200mg/kgbw Oligonol or 200mg/kgbw lychee polyphenol for 90 days. Oligonol did not show any potential to induce gene mutations in reverse mutation tests using Salmonella typhimurium TA98, TA100, TA1535, TA1537 and Escherichia coli WP2uvrA strains. Oligonol did not induce chromosomal aberrations in cultured Chinese hamster lung cells, but it showed increased polyploidy. In a micronucleus assay in mice, Oligonol did not induce any micronuclei or suppress bone marrow, indicating it does not cause chromosome aberrations. The results from these safety studies and previous reports support the safety of Oligonol for human consumption.

 

 

Get the whole article here

Author: Stéphane Bastianetto and Slavica Krantic and Rémi Quirion

Background: It has been suggested that accumulation of amyloid-beta (Aß) peptides into senile plaques plays a pivotal role in neuronal cell death occuring in Alzheimer's disease (AD). Aß produces two major types of programmed cell death (PCD) in vitro which requires the activation of effectors of caspase-dependent and -independent cell death pathways, namely caspase-3 and apoptosis inducing factor (AIF). Published data comparing the expression of AIF in post-mortem brains from AD patients and neurologically normal subjects in the course of aging suggest the relevance of AIF in the pathogenesis of AD Reix et al, Neurobiol Aging 28:351, 2007; Yu et al., Am. J. Path., in press). Recent epidemiological studies have reported that elderly people have a lower risk (up to 50%) to develop AD if they regularly eat fruits and vegetables and drink a moderate amount of tea and red wine. Numerous studies indicate that polyphenols derived from these foods and beverages account for the observed neuroprotective effects. In particular, polyphenols extracted from green tea (i.e. epigallocatechin gallate or EGCG) or red wine (i.e. resveratrol) blocked hippocampal cell death against Aß-induced toxicity (Bastianetto et al, Eur J Neurosci 23:55, 2006; Han et al, Br J Pharmacol 141:997, 2004). Our main objective is to determine whether concurrent inactivation of both main types of PCD may have additive therapeutic benefit in AD. Methods: Mixed hippocampal cell cultures were prepared from E19 fetuses obtained from Sprague-Dawley rats. They were grown in D-MEM high glucose containing 10% (v/v) fetal bovine serum. Experiments were performed in 6-day-old cultures. Results: The 24-hour exposure of cultured hippocampal cells to Aß1-42 (15 μM) alone or in combination with either resveratrol (20 μM) or EGCG (10 μM) reduced Aß1-42-mediated increased expression of the 57 kDa death-inducing form of AIF. Moreover, EGCG completely inhibited the activation of the key apoptotic executioner, caspase-3, and reduce the number of apoptotic cells, whereas resveratrol was less effective. Conclusions: Our findings show that these polyphenols do not share the same mechanism of action, suggesting that a combination of EGCG and resveratrol might provide additional neuroprotection against Aß-associated cell death.

 

Get the whole article here

Author: Ian T Johnson

Despite being one of the most widely consumed beverages in the world, green tea is often seen by the media as a so-called superfood, attributed with various health benefits including protective effects against cancer. This reputation rests primarily on the fact that green tea is a rich source of polyphenols, which provide much of the colour and aroma of tea. Both green and black varieties are aqueous infusions of the plant Camellia sinensis, but whereas the constituent polyphenols of black tea are allowed to become oxidised to theaflavins during processing, green tea leaves are heat-treated to inactivate their polyphenol oxidase activity, enabling the native catechins to remain intact.

 

 

Get the whole article here

Author: Yoshinori Fujimura and Shuntaro Tsukamoto and Miho Irie and Daisuke Miura and Hiroyuki Miura and Hirofumi Tachibana

 

Get the whole article here

Author: Joshua D. Lambert and Ryan J. Elias

Green tea (Camellia sinensis) is rich in catechins, of which (−)-epigallocatechin-3-gallate (EGCG) is the most abundant. Studies in animal models of carcinogenesis have shown that green tea and EGCG can inhibit tumorigenesis during the initiation, promotion and progression stages. Many potential mechanisms have been proposed including both antioxidant and pro-oxidant effects, but questions remain regarding the relevance of these mechanisms to cancer prevention. In the present review, we will discuss the redox chemistry of the tea catechins and the current literature on the antioxidant and pro-oxidative effects of the green tea polyphenols as they relate to cancer prevention. We report that although the catechins are chemical antioxidants which can quench free radical species and chelate transition metals, there is evidence that some of the effects of these compounds may be related to induction of oxidative stress. Such pro-oxidant effects appear to be responsible for the induction of apoptosis in tumor cells. These pro-oxidant effects may also induce endogenous antioxidant systems in normal tissues that offer protection against carcinogenic insult. This review is meant point out understudied areas and stimulate research on the topic with the hope that insights into the mechanisms of cancer preventive activity of tea polyphenols will result.

 

Get the whole article here

Author: Tomomi Kinoshita and Satoshi Hirata and Ziyin Yang and Susanne Baldermann and Emiko Kitayama and Shigetaka Matsumoto and Masayuki Suzuki and Peter Fleischmann and Peter Winterhalter and Naoharu Watanabe

Damascenone is well-known for its potent flavour with an extremely low odour threshold. Several glycosidically bound precursors of damascenone have been isolated from several plants, but little is known about their occurrences in green tea infusions. In this work, three major glycosidic precursors of damascenone, 9-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1a), 9-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2a), and 3-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2b) were isolated and identified in green tea infusions, and the stereochemistries at C-3 and C-9 positions of aglycone parts of the three glycosidic precursors were determined as (3S, 9R)-1a, (3R, 9R)-2a, and (3R, 9R)-2b, respectively. Compounds 1a, 2a, and 2bas well as 3-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1b) were hydrolysed to form damascenone in a model system with strong acidic conditions (pH 2.0) and at high temperature (90 °C). In contrast to hydrolysis of 2a and 2b, more damascenone was transformed from 1a and 1b. Furthermore, the β-d-glucosyl moiety at the C-3 position gave a higher dehydration rate from megastigma-6,7-dien-3,5,9-triol to 3-hydroxy-7,8-didehydro-β-ionol than compound 1a carrying the sugar residue at C-9 position. Interestingly, the four glycosidic precursors of damascenone were not hydrolysed to give damascenone under slightly acidic conditions (pH 5.4 and 120 °C for 10 min), but they could be transformed to damascenone in the presence of green tea infusions even under the equal conditions.

 

Get the whole article here