Research Database

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.

 

 

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Author: P. Valentão and E. Fernandes and F. Carvalho and P.B. Andrade and R.M. Seabra and M.L. Bastos

Summary Small centaury (Centaurium erythraea Rafin.) is a herbal species with a long use in traditional medicine due to its digestive, stomachic, tonic, depurative, sedative and antipyretic properties. This species is reported to contain considerable amounts of polyphenolic compounds, namely xanthones and phenolic acids as the main constituents. Although the antiradicalar activity of some pure polyphenolic compounds is already known, it remains unclear how a complex mixture obtained from plant extracts functions against reactive oxygen species. Thus, the ability of small centaury infusion to act as a scavenger of the reactive oxygen species hydroxyl radical and hypochlorous acid was studied and compared with that of green tea (Camellia sinensis L.). Hydroxyl radical was generated in the presence of Fe3+-EDTA, ascorbate and H2O2 (Fenton system) and monitored by evaluating hydroxyl radical-induced deoxyribose degradation. The reactivity towards hypochlorous acid was determined by measuring the inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5′-dithiobis(2-nitrobenzoic acid). The obtained results demonstrate that small centaury infusion exhibits interesting antioxidant properties, expressed both by its capacity to effectively scavenge hydroxyl radical and hypochlorous acid, although with a lower activity against the second than that observed for green tea. Green tea exhibited a dual effect at the hydroxyl radical scavenging assay, stimulating deoxyribose degradation at lower dosages.

 

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Author: M.F. Melzig and M. Janka

Green tea extract (EFLA®85942) is able to induce specifically the neutral endopeptidase (NEP) activity and to inhibit the proliferation of SK-N-SH cells; the angiotensin-converting enzyme (ACE) activity is not influenced under the same conditions. The treatment of the cells with arabinosylcytosine and green tea extract results in a strong enhancement of cellular NEP activity whereas cellular ACE activity was not changed significantly, indicating a green tea extract-specific regulation of NEP expression. Because of its role in the degradation of amyloid beta peptides this enzyme induction of NEP by long term treatment with green tea extract may have a beneficial effect regarding the prevention of forming amyloid plaques.

 

 

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Author: J.J. Choo

The aim of the present study was to investigate body fat-suppressive effects of green tea in rats fed on a high-fat diet and to determine whether the effect is associated with β-adrenoceptor activation of thermogenesis in brown adipose tissue. Feeding a high-fat diet containing water extract of green tea at the concentration of 20g/kg diet prevented the increase in body fat gain caused by high-fat diet without affecting energy intake. Energy expenditure was increased by green tea extract which was associated with an increase in protein content of interscapular brown adipose tissue. The simultaneous administration of the β-adrenoceptor antagonist propranolol(500 mg/kg diet) inhibited the body fat-suppressive effect of green tea extract. Propranolol also prevented the increase in protein content of interscapular brown adipose tissue caused by green tea extract. Digestibility was slightly reduced by green tea extract and this effect was not affected by propranolol. Therefore it appeared that green tea exerts potent body fat-suppressive effects in rats fed on a high-fat diet and the effect was resulted in part from reduction in digestibility and to much greater extent from increase in brown adipose tissue thermogenesis through β-adrenoceptor activation.

 

 

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Author: Phing Chian Chai and Lee Hua Long and Barry Halliwell

Green tea and red wine are claimed to have health benefits because of their high content of polyphenolic compounds, but they have also been reported as mutagenic in some test systems. In this paper, we show that a commonly used cell culture medium, Dulbecco’s modified Eagle’s medium (DMEM), catalyses oxidation of green tea and red wines to generate H2O2. The level of H2O2produced from green tea accounted for all of the cytotoxic effects of this beverage on PCl2 cells. By contrast, H2O2 was only responsible for part of the cytotoxicity of the red wines examined. Our data illustrate the danger of extrapolating from cell culture studies to predict the effects of complex beverages in vivo.

 

 

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Author: Richard Béliveau and Denis Gingras

 

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Author: Tsung O. Cheng

 

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Author: Sheng Biao Wan and Di Chen and Q. Ping Dou and Tak Hang Chan

The green tea polyphenol catechin-3-gallate (CG) and epicatechin-3-gallate (ECG) were synthesized enantioselectively via a Sharpless hydroxylation reaction followed by a diastereoselective cyclization. Their potencies to inhibit the proteasome activity were measured. The unnatural enantiomers were found to be equally potent to the natural compounds.

 

 

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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.

 

 

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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.

 

 

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