Research Database

Author: Alissana Ester Iakmiu Camargo and Danielle Alessandra Erdei Daguer and Decio Sabbatini Barbosa

Antioxidant defenses can be characterized as agents (enzymes and low-molecular-mass antioxidants) in biological systems that prevent the noxious action of free radicals or other reactive species. The present study examined whether the use of green tea may exert antioxidant action in vitro and improve antioxidant defenses and serum lipids in normal and dyslipidemic subjects. Forty-one hypercholesterolemic individuals, 18 women and 23 men (age [mean ± SD], 44.81 ± 14.41), were evaluated before and after the daily intake of 6 g of green tea in 500 mL of water for 1 month. Likewise, 27 normolipidemic individuals, 12 women and 15 men (age, 37.07 ± 16.08), were also evaluated. Serum lipids were measured by an automated clinical chemistry system. The total serum antioxidant potential (TRAP) and serum levels of lipid hydroperoxides were quantified using the chemiluminescence method. Total polyphenols present in green tea ingested by the patients were verified by using Folin-Ciocalteau reagent. The in vitro evaluation of green tea antioxidant activity was performed using microsomes obtained from rat liver, which was oxidized by tert-butyl hydroperoxide. From this system, thiobarbituric acid reactive substances were measured. In the in vitro test, green tea polyphenols proved to be efficient at protecting microsomes from the oxidant activity of tert-butyl hydroperoxide. There were no significant alterations in the lipid profiles of the normolipidemic or hypercholesterolemic subject groups. Although there was no decrease in lipid hydroperoxides, both groups showed increased antioxidant defenses, which was evidenced by TRAP. In conclusion, the results obtained indicate that besides achieving antioxidant action in vitro, the consumption of green tea increased the TRAP of normal and dyslipidemic subjects.

 

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Author: A. Soussi and Y. Gaubin and B. Beau and J.C. Murat and J.P. Soleilhavoup and F. Croute and A. El Feki

Expression pattern of heat shock proteins (Hsp) 72/73 and glucose regulated protein (Grp) 94 was studied in liver, kidney and testis of rats injected with sublethal doses of ammonium metavanadate (5 mg/kg/day). In addition, some batches of animals were given green tea decoction, known to be rich in anti-oxidative compounds, as sole beverage in order to evaluate its protective properties. In control animals, the stress proteins expression was found to be organ-dependant: anti-Grp94 antibody revealed two bands at 96 and 98 kDa in kidney and liver whereas the 98 kDa band only was found in testis; anti-Hsp72/73 antibody revealed that the constitutive Hsp73 was present in all organs whereas the inducible Hsp72 was only present in kidney and testis. In kidney of vanadium-treated rats, Hsp73 was over-expressed by about 50% whereas Hsp72 was down-regulated by 50–80%. No such effects were observed in liver and testis. In liver and kidney of vanadium-treated rats, Grp94 was over-expressed by 50% and 150% respectively whereas no change was found in testis. In rats given green tea as sole beverage, the 96 kDa protein expression level in liver was reduced both in controls and in vanadium-treated animals. However, green tea drinking failed to prevent the vanadium-induced Hsp72 under-expression in kidney of vanadium-treated rats.

 

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Author: Hüseyin Bozkurt

Effect of natural (green tea extract, Thymbra spicata oil) and synthetic antioxidants (buthylatedhydroxytoluene, BHT) on the safety (biogenic amine and TBARS values) and quality (pH, colour and sensory attributes) of sucuk (Turkish dry-fermented sausage) were investigated during the ripening periods. Addition of antioxidants decreased (P < 0.05) the TBARS values. It was found that natural antioxidants decreased TBARS formation more than BHT. Antioxidants reduced (P < 0.05) putrescine formation in the following order: green tea extract > green tea extract–T. spicata oil > T. spicata oil > BHT, and their mean values were 70.45, 76.05, 83.13, and 95.97 mg/kg, respectively. The highest tyramine concentration was observed in control sucuk prepared without any antioxidants, while the lowest was in the recipe with green tea extract as their mean values were about 99.42 and 64.31 mg/kg, respectively. The pH, L, b, and overall sensory quality were not significantly different (P > 0.05) with the addition of green tea extract, T. spicata oil, green tea extract–T. spicata oil. These results indicated that the most effective antioxidant was found to be green tea extract. This study pointed out that natural antioxidants were more effective than synthetic antioxidants, so they could be easily utilized in sucuk to enhance quality and provide safer products.

 

 

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Author: Maria Kapsokefalou and Le Zhu and Dennis D. Miller

Author: S.S. Bun and H. Bun and D. Guédon and C. Rosier and E. Ollivier

An herbal medicinal product (Exolise®) containing as active ingredient an hydro-alcoholic extract of green tea named AR25® (standardized to 25% catechins) has been implicated in hepatic failures, leading to the withdrawal of the marketing authorization. The active ingredient of Exolise® being manufactured with 80% ethanol, the question to know whether the extraction solvent could introduce some toxic components was hypothesized. Two investigations were conducted in Wistar rats to determine if repeated oral administration of different green tea extracts could corroborate the reported hepatotoxicity in humans. In a preliminary 6 week-study, experimental groups (n = 9/group) received either the vehicle or a methylene chloride extract (2500 mg/kg body weight) where potential non-polar hepatotoxin(s) could be concentrated. In a second experiment (12 week-study), rats were divided in three groups (n = 10/group) and treated with either the vehicle, or an aqueous extract (1400 mg/kg) or AR25® green tea extract (2000 mg/kg). Rat liver functions were assessed by serum biochemistry of hepatotoxicity markers. No sign of evidence of characteristic hepatotoxicity was found in rats treated with very high amount of different green tea extracts in these two experiments (respectively a daily dosage, which was about 900 and 80 times higher to the therapeutic daily dosage of Exolise®).

 

 

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Author: Pon Velayutham Anandh Babu and Kuruvimalai Ekambaram Sabitha and Chennam Srinivasulu Shyamaladevi

Hyperglycemia induced oxidative stress has been proposed as a cause of many complications of diabetes including cardiac dysfunction. The present study depicts the therapeutic effect of green tea extract on oxidative stress in aorta as well as heart of streptozotocin diabetic rats. Six weeks after diabetes induction, green tea was administered orally for 4 weeks [300 mg (kg body weight)−1 day−1]. In aorta and heart of diabetic rats there was a significant increase in the activity of superoxide dismutase, catalase and glutathione peroxidase with an increase in lipid peroxides. Diabetic rats showed a significant decrease in the levels of serum and cardiac glutathione. Green tea administration to diabetic rats reduced lipid peroxides and activity of antioxidant enzymes whereas increased glutathione content. The results demonstrate that the induction of antioxidant enzymes in diabetic rats is not efficient and sufficient to reduce the oxidative stress. But green tea by providing a competent antioxidative mechanism ameliorates the oxidative stress in the aorta and heart of diabetic rats. The study suggests that green tea may provide a useful therapeutic option in the reversal of oxidative stress induced cardiac dysfunction in diabetes mellitus.

 

 

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Author: Alessandra Gamberucci and Laura Konta and Angela Colucci and Roberta Giunti and Judit É. Magyar and József Mandl and Gábor Bánhegyi and Angelo Benedetti and Miklós Csala

Green tea is getting into the focus of scientific interest due to its beneficial health effects, most of which are attributed to its catechin content. Polyphenolic tea catechins have antioxidant, antiproliferative, antiangiogenic and proapoptotic effects, which makes them promising anticancer compounds. Other poly-hydroxy molecules have similar antitumor potentials through the inhibition of glucosidase II, which affects the glycoprotein maturation and quality control in the endoplasmic reticulum. We investigated the effect of tea catechins on glucosidase II activity in rat liver microsomes using 4-methylumbelliferyl glucoside and 4-nitrophenyl glucoside as substrates. A concentration-dependent inhibition with non-competitive kinetics was found. The IC50 and Ki values for certain tea catechins were comparable with those of N-butyldeoxynojirimycin, the widely used glucosidase inhibitor. The possible interference of tea catechins with the glycoprotein processing in the endoplasmic reticulum should be considered as a potential mechanism of their dietary or pharmacological effects.

 

 

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Author: K. Diepvens and E.M.R. Kovacs and N. Vogels and M.S. Westerterp-Plantenga

The effect of ingestion of green tea (GT) extract along with a low-energy diet (LED) on health-related blood parameters, and the relationships among changes in metabolic parameters and phases of weight loss were assessed. A double-blind, placebo-controlled, parallel design was used. 46 female subjects (BMI 27.7 ± 1.8 kg/m2) were fed in energy balance from days 1 to 3, followed by a LED with GT (n = 23) or placebo (PLAC, n = 23) from days 4 to 87. The LED-period consisted of a phase 1 of 4 weeks (days 4–32) followed by a phase 2 of 8 weeks (days 32–87). Body composition and fasting blood samples were determined on days 4, 32 and 87. No significant differences were observed between the blood parameters of the PLAC and GT group. In phase 1 compared to phase 2 the rate of weight loss was 0.09 ± 0.05 kg/day vs. 0.03 ± 0.03 kg/day (p < 0.001); Fat free mass (FFM) was 21% of weight loss in phase 1 vs. 7% in phase 2 (ns). Surprisingly, favourable changes in free fatty acids, triacylglycerol, β-hydroxybutyrate, glucose and total cholesterol in phase 1 were reversed in phase 2 (p < 0.01). Taken together, GT supplementation during a LED had no effect on health-related blood parameters. Initial improvements in several blood measures at day 32 were reversed by day 87, despite continued weight loss. Modest weight loss improved HDL cholesterol and blood pressure.

 

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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: Tsung O. Cheng

Tea is one of the most widely consumed beverages in the world, next only to water. It can be categorized into three types, depending on the level of fermentation, i.e., green (unfermented), oolong (partially fermented) and black (fermented) tea. In general, green tea has been found to be superior to black tea in terms of antioxidant activity owing to the higher content of (−)-epigallocatechin gallate. The processes used in the manufacture of black tea are known to decrease levels of the monometric catechins to a much greater extent than the less severe conditions applied to other teas. The cardioprotective effect of flavonoids from green tea can be attributed to not only antioxidant, antithrombogenic and anti-inflammatory properties but also improvement of coronary flow velocity reserve. In this article, I will discuss the effects of green tea on atherosclerosis, coronary heart disease, hypertension, diabetes, metabolic syndrome and obesity, and, finally, its comparison with black tea.

 

 

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