cognitive-function

Author: Anna C Nobre PhD and Anling Rao PhD and Gail N Owen PhD

Tea is the most widely consumed beverage in the world after water. Tea is known to be a rich source of flavonoid antioxidants. However tea also contains a unique amino acid, L-theanine that may modulate aspects of brain function in humans. Evidence from human electroencephalograph (EEG) studies show that it has a direct effect on the brain (Juneja et al. Trends in Food Science & Tech 1999;10;199-204). L-theanine significantly increases activity in the alpha frequency band which indicates that it relaxes the mind without inducing drowsiness. However, this effect has only been established at higher doses than that typically found in a cup of black tea (~20mg). The aim of the current research was to establish this effect at more realistic dietary levels. EEG was measured in healthy, young participants at baseline and 45, 60, 75, 90 and 105 minutes after ingestion of 50mg L-theanine (n=16) or placebo (n=19). Participants were resting with their eyes closed during EEG recording. There was a greater increase in alpha activity across time in the L-theanine condition (relative to placebo (p<0.05). A second study replicated this effect in participants engaged in passive activity. These data indicate that L-theanine, at realistic dietary levels, has a significant effect on the general state of mental alertness or arousal. Furthermore, alpha activity is known to play an important role in critical aspects of attention, and further research is therefore focussed on understanding the effect of L-theanine on attentional processes.

Get the whole article here

Author: Tohru Hasegawa

Get the whole article here

Author: V Nwuha

Membrane extraction of the bioactive components of green tea in an organic solvent has been investigated using different nanofiltration membranes. Different concentrations of ethanol (10%, 20%, 50% and 80%) were used as the organic solvent. Membrane separation performance of bioactive components of green tea showed some changes in flux and solute rejection with negligible change in membrane stability. Special attention was focused on the removal of caffeine from the solution mixture of the green tea extract while retaining the group of catechins known as polyphenols. A series of tests with various membranes using higher ethanol concentrations (e.g. 80%) gave highest rejection of catechins with lower rejection of caffeine for G-10 and G-20 membranes, respectively. The rejection using HC-50 and HR98PP membranes were fairly good but the pure ethanol fluxes under the same pressure (5.0 MPa) were not promising for this solvent.

Get the whole article here

Author: J.H Weisburger and Fung-Lung Chung

The beverage tea, from the top leaves of the plant Camellia sinensis is one of the most widely used beverages in the world, second only to water. Black and green tea have mostly similar actions. The active components are polyphenols, mainly epigallocatechin gallate in green tea, and the tea leaf polyphenol oxidase mediated oxidation to oolong and black tea, yielding other polyphenols, theaflavin and thearubigins. There is 40−50 mg caffeine in a 160-ml cup of tea. The chemopreventive effects of tea depend on: (1) its action as an antioxidant; (2) the specific induction of detoxifying enzymes; (3) its molecular regulatory functions on cellular growth, development and apoptosis; and (4) a selective improvement in the function of the intestinal bacterial flora. The oxidation of LDL cholesterol, associated with a risk for atherosclerosis and heart disease, is inhibited by tea. Many of cancers are caused by lifestyle elements. One is cigarette and tobacco use, leading to cancer in the oral cavity, esophagus and lung, inhibited by tea. Mice administered a tobacco nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), developed significantly fewer lung tumors than controls when given green tea or its major polyphenol, epigallocatechin gallate (EGCG). Tea suppressed the formation of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, in the lung DNA of mice given NNK. Gastric cancer, caused by a combination of Helicobacter pylori and salted foods, is lower in tea drinkers. Western nutritionally-linked cancers of the breast, colon, prostate and pancreas can be inhibited by tea. The formation of genotoxic carcinogens for these target organs during the cooking of meats, heterocyclic amines, and their effects were decreased by tea. Tea inhibited the formation of reactive oxygen species and radicals and induced cytochromes P450 1A1, 1A2 and 2B1, and glucuronosyl transferase. The higher formation of glucuronides represents an important mechanism in detoxification. The developmental aspects and growth of cancers through promotion are decreased by tea. The regular use of a widely available, tasty, inexpensive beverage, tea, has displayed valuable preventive properties in chronic human diseases.

Get the whole article here

Author: David J. Weiss and Christopher R. Anderton

Catechins in green tea are known to have many beneficial health properties. Recently, it has been suggested that matcha has greater potential health benefits than other green teas. Matcha is a special powdered green tea used in the Japanese tea ceremony. However, there has been no investigation to quantitate the catechin intake from matcha compared to common green teas. We have developed a rapid method of analysis of five catechins and caffeine in matcha using micellar electrokinetic chromatography. Results are presented for water and methanol extractions of matcha compared with water extraction of a popular green tea. Using a mg catechin/g of dry leaf comparison, results indicate that the concentration of epigallocatechin gallate (EGCG) available from drinking matcha is 137 times greater than the amount of EGCG available from China Green Tips green tea, and at least three times higher than the largest literature value for other green teas.

Get the whole article here

Author: Larisa Lvova and Andrey Legin and Yuri Vlasov and Geun Sig Cha and Hakhyun Nam

All-solid-state ‘electronic tongue’ microsystem comprised of polymeric sensors of different types such as highly cross-sensitive sensors based both on \{PVC\} and aromatic polyurethane (ArPU) matrices doped with various membrane active components, electrochemically deposited conductive films of polypyrrole (PPy) and polyaniline (PAn) and potentiometric glucose biosensors has been developed and applied for the analysis of beverages: natural coffee, black tea and different sorts of green teas. The system can discriminate different kinds of teas (black and green) and natural coffees. Components that are responsible for giving unique taste such as caffeine, catechines, sugar, amino acid l-arginine have been determined for green tea samples with unknown manufacturer specifications.

Get the whole article here

Author: Satoshi Matsubara and Hideyuki Shibata and Fumiyasu Ishikawa and Teruo Yokokura and Mami Takahashi and Takashi Sugimura and Keiji Wakabayashi

Since urease of Helicobacter pylori is essential for its colonization, we focused attention on foodstuffs which inhibit the activity of this enzyme. Among plant-derived 77 foodstuff samples tested, some tea and rosemary extracts were found to clearly inhibit H. pylori urease in vitro. In particular, green tea extract (GTE) showed the strongest inhibition of H. pylori urease, with an IC50 value of 13 μg/ml. Active principles were identified to be catechins, the hydroxyl group of 5′-position appearing important for urease inhibition. Furthermore, when H. pylori-inoculated Mongolian gerbils were given GTE in drinking water at the concentrations of 500, 1000, and 2000 ppm for 6 weeks, gastritis and the prevalence of H. pylori-infected animals were suppressed in a dose-dependent manner. Since the acquisition by H. pylori of resistance to antibiotics has become a serious problem, tea and tea catechins may be very safe resources to control H. pylori-associated gastroduodenal diseases.

Get the whole article here

Author: H. Osman and R. Nasarudin and S.L. Lee

Cocoa shoot (CS), young leaves (CL) and tea leaves (GT) were processed according to green tea processing procedures. Polyphenol components was extracted and analysed using high pressure liquid chromatography. The total polyphenol of CS, CL and GT were 19.0, 28.4 and 17.3 mg/100 mg, respectively. The main catechin-polyphenols in extracts were epicatechin (EC), epigallocatechin gallate (EGCG), epigallocatechin (EGC), gallic acid (GA) and epicatechin gallate (ECG). The concentrations of caffeine for CS, CL and GT were 2.24, 1.33 and 3.34 mg/100 mg, respectively. The concentrations of EGCG, in both cocoa leaves, were lower than commercial green tea. However, the concentrations of EC in CS (5.93 mg/100 mg) and in CL (2.82 mg/100 mg) were significantly higher that those found in green tea (0.65 mg/100 mg). The antioxidation properties of the polyphenol extracts were tested, using ferric chloride reduction, and compared against a synthetic antioxidant (BHA). The polyphenol extracts (CS and CL) showed similar antioxidation powers to GT and BHA throughout the entire concentration range (100–2000 ppm). In the oil-based test medium; the antioxidative performance of polyphenol extracts were better than BHA at 50 ppm. At 200 ppm, the performance is quite similar to BHA. At higher concentration (400 ppm) the antioxidant activities are much better than BHA. In the presence of Cu2+ prooxidant (20 ppm), BHA (200 ppm) and all the extracts (200 pmm) showed similar performances. Since the oxidation test was conducted at 65 °C, the 8 days of stability provided by 200 ppm addition of CL and CS extracts, can be equated to 8 months of room temperature (25 °C) stability. Hence, the cocoa leaves extracts have the potential to complement or replace synthetic antioxidants in aqueous and oil-based food applications.

Get the whole article here

Author: Rachel J. Batchelder and Richard J. Calder and Chris P. Thomas and Charles M. Heard

The aim of this study was to investigate the feasibility of the transdermal delivery of catechins and caffeine from green tea extract. Drug-in-adhesive patches containing 1.35, 1.03, 0.68, and 0.32 mg cm−2 green tea extract were formulated and the dissolution of (−)-epigallocatechin gallate (EGCg), (−)-epigallocatechin (EGC) and (−)-epicatechin (EC) from these was determined. Transdermal delivery was determined across full thickness pig ear skin from saturated solutions of green tea extract in pH 5.5 citrate–phosphate buffer, polyethylene glycol 400 and a 50:50 mixture of the citrate phosphate buffer and polyethylene glycol in addition to patches containing 1.35 mg cm−2 green tea extract. Dissolution experiments indicated first order release which was dose dependent in respect of the loading level, although the amounts permeated were not always proportional to the amounts in the formulation. The highest percentage permeation of EGCg was found to be from the patch formulation. EGCg, EGC and EC were all successfully delivered transdermally from saturated solutions and adhesive patches containing green tea extract in this study. There was some evidence for the dermal metabolism of EGCg, but after 24 h 0.1% permeated from the patches containing 1.35 mg cm−2 green tea extract. This was equivalent to the percentage absorbed after intragastric administration of green tea extract in rats. In addition, the concentration of EGCg in the Franz cell receptor chamber after 24 h permeation from the 0.9 cm diameter patch containing 1.35 mg cm−2was within the range of Cmax plasma levels achieved after oral dosing of 2.2–4.2 g m−2 green tea extract. Caffeine was also delivered at concentrations above those previously reported.

Get the whole article here

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.

Get the whole article here