cognitive-function

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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PLE in the analysis of plant compounds: Part I. The application of PLE for HPLC analysis of caffeine in green tea leaves

Author: Andrzej L. Dawidowicz and Dorota Wianowska

A broad spectrum of sample preparation methods is currently used for the isolation of pharmacologically active compounds from plant and herbal materials. The paper compares the effectiveness of infusion, microwave assisted solvent extraction (MASE), matrix solid-phase dispersion (MSPD) and pressurised liquid extraction (PLE) as sample preparation methods for the isolation of caffeine from green tea leaves. The effect of PLE variables, such as extraction temperature, pressure and time, on the yield of caffeine from the investigated matrix is discussed. The obtained results revealed that PLE, in comparison with other sample preparation methods applied, has significantly lower efficacy for caffeine isolation from green tea leaves. The evaluation of PLE conditions leads to the conclusion that elevated pressure applied in the PLE process is the factor hindering the extraction.

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Author: David Labbé and Monica Araya-Farias and Angelo Tremblay and Laurent Bazinet

Epigallocatechin gallate (EGCG) is regarded as the most important of the tea catechins. Therefore, methods for producing tea extracts with high EGCG content have been developed. However, these methods have the disadvantages to use solvent or to allow the purification of small volumes. The aim of this exploratory study was to evaluate the feasibility of selectively extracting catechins and caffeine from a green tea solution using an electrodialysis cell. Commercially available membranes (AMX-SB, AFN, PC-400 D and UF-1000 Da) were tested for their potential to allow migration of green tea catechins. This study demonstrated that epigallocatechin (EGC) and EGCG from a green tea infusion can migrate at a high rate through an electrodialysis (ED) system. Among tested membranes, the UF-1000 Da membrane can achieve an EGC and EGCG migration as high as 50%. The other studied catechins and caffeine had no significant migration rate through either the anionics or the UF membranes. Thus, this method combined to a previously developed EGCG preconcentration procedure might allow the production of a green tea extract with highly active biological compound.

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Author: M. Schmidt and H.-J. Schmitz and A. Baumgart and D. Guédon and M.I. Netsch and M.-H. Kreuter and C.B. Schmidlin and D. Schrenk

Author: Margriet Westerterp-Plantenga and Kristel Diepvens and Annemiek M.C.P. Joosen and Sonia Bérubé-Parent and Angelo Tremblay

Consumption of spiced foods or herbal drinks leads to greater thermogenesis and in some cases to greater satiety. In this regard, capsaicin, black pepper, ginger, mixed spices, green tea, black tea and caffeine are relevant examples. These functional ingredients have the potential to produce significant effects on metabolic targets such as satiety, thermogenesis, and fat oxidation. A significant clinical outcome sometimes may appear straightforwardly but also depends too strongly on full compliance of subjects. Nevertheless, thermogenic ingredients may be considered as functional agents that could help in preventing a positive energy balance and obesity.

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Author: David Labbé and Angelo Tremblay and Laurent Bazinet

In an industrial context of producing catechin-enriched fractions by electromigration, a new technology demonstrated to be effective for concentration of the two main catechins (EGC and EGCG) of green tea, the recovery yield from tea leaves during brewing would be the most important parameter of the whole process rentability. However, the majority of the kinetic studies were carried-out on black tea, a fermented tea. Consequently, the objective of this study was to investigate the effects of temperature (50, 60, 70, 80 and 90 °C) and brewing duration (0, 5, 10, 20, 40 and 80 min) on the catechin solubilization from green tea, a non-fermented tea. The use of mathematical models revealed that there was a variable interdependence between the brewing duration and the brewing temperature on catechin and caffeine concentrations. It was possible to divide catechins in two groups, the time dependent compounds (EGC and EC) and the time/temperature dependent compounds (C, EGCG, GCG and ECG). Furthermore, the 3D models calculated to represent the evolution of the catechins and caffeine concentrations allowed to determine the best combination of time and temperature for their extraction: 50 °C during 20–40 min for time-dependent compounds, 90 °C during 80 min for the time/temperature-dependent compounds, and 70–80 °C during 20–40 min for caffeine. Furthermore, this research pointed out a very simple two-step procedure to fractionate the EGC and EGCG by modifying brewing temperature and time parameters.

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Author: Nurulain T. Zaveri

Can drinking several cups of green tea a day keep the doctor away? This certainly seems so, given the popularity of this practice in East Asian culture and the increased interest in green tea in the Western world. Several epidemiological studies have shown beneficial effects of green tea in cancer, cardiovascular, and neurological diseases. The health benefits associated with green tea consumption have also been corroborated in animal studies of cancer chemoprevention, hypercholesterolemia, artherosclerosis, Parkinson's disease, Alzheimer's disease, and other aging-related disorders. However, the use of green tea as a cancer chemopreventive or for other health benefits has been confounded by the low oral bioavailability of its active polyphenolic catechins, particularly epigallocatechin-3-gallate (EGCG), the most active catechin. This review summarizes the purported beneficial effects of green tea and EGCG in various animal models of human diseases. Dose-related differences in the effects of EGCG in cancer versus neurodegenerative and cardiovascular diseases, as well as discrepancies between doses used in in vitro studies and achievable plasma understanding of the in vivo effects of green tea catechins in humans, before the use of green tea is widely adopted as health-promoting measure.

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Author: Brad A. Sutherland and Rosanna M.A. Rahman and Ian Appleton

Catechins are dietary polyphenolic compounds associated with a wide variety of beneficial health effects in vitro, in vivo and clinically. These therapeutic properties have long been attributed to the catechins' antioxidant and free radical scavenging effects. Emerging evidence has shown that catechins and their metabolites have many additional mechanisms of action by affecting numerous sites, potentiating endogenous antioxidants and eliciting dual actions during oxidative stress, ischemia and inflammation. Catechins have proven to modulate apoptosis at various points in the sequence, including altering expression of anti- and proapoptotic genes. Their anti-inflammatory effects are activated through a variety of different mechanisms, including modulation of nitric oxide synthase isoforms. Catechins' actions of attenuating oxidative stress and the inflammatory response may, in part, account for their confirmed neuroprotective capabilities following cerebral ischemia. The versatility of the mechanisms of action of catechins increases their therapeutic potential as interventions for numerous clinical disorders. However, more epidemiological and clinical studies need to be undertaken for their efficacy to be fully elucidated.

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Author: Amra Perva-Uzunalić and Mojca Škerget and Željko Knez and Bernd Weinreich and Frank Otto and Sabine Grüner

The effect of different extraction set-ups that influence the extraction efficiency of catechins and caffeine from green tea leaves (variety Fanning Belas, China) were studied using different aqueous and pure solvents (acetone, ethanol, methanol, acetonitrile, water), different temperatures (60, 80, 95 and 100 °C) and times (5–240 min). Raw extracts were analysed for contents of major catechins (EC, EGC, ECG, EGCG), caffeine, proanthocyanidins and flavonols (myricetin, caempherol, quercetin). Starting material was found to contain 191 g major catechins/kg material, 36 g caffeine/kg material and 5.2 g flavonols/kg material on a dry mass basis. The content of major catechins in green tea extracts varied from approximately 280–580 g/kg dry extract, with extraction efficiencies of major catechins varying from 61% to almost 100%. Content of caffeine in extract was in the range of 75 g/kg, where its extraction efficiency varied from 62% to 76%. Average extraction yield was 30% with exceptions when using pure acetone and acetonitrile, where extraction yield was about 3%. Contents of flavonols and proanthocyanidins were in the ranges 6–20 and 12–19 g/kg, respectively. Different extraction procedures with water were also investigated and optimal conditions determined: maximum achieved extraction efficiency of catechins with water was obtained at 80 °C after 20 min (97%) and at 95 °C after 10 min of extraction (90%). Degradation of catechins was observed at higher extraction temperatures and with prolonged extraction times. Using a lower ratio of solvent to material, extraction efficiencies were increased by applying a multi-step extraction procedure. Optimal extraction procedure was then performed using decaffeinated green tea leaves, which were obtained by high-pressure extraction with CO2, when 98% of caffeine was selectively isolated without significant impact on valuable catechins.

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Author: A. Reed and B. Raudenbush

Previous research indicates green tea extract can have beneficial effects on health and performance. The present study was designed to determine the extent to which green tea extract significantly impacts cognitive functioning, endurance, perceived workload, and mood over time. Participants were 18 student athletes who were tested over a 6-week time period. Results of the experiment reveal athletes show a significant improvement in the number of push-ups completed when given green tea extract. No statistically significant improvements were found for cognition, mood, or perceived workload; however, the majority of these measures were greater in the green tea condition. The implication of these results is that natural, and in the case of green tea, very healthy, substances could be used to enhance endurance, rather than pharmacological methods such as caffeine and steroids.

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