Anti-oxidant properties of Tea
Calzuola I, Gianfranceschi GL, Marsili V. Dipartimento di Biologia Cellulare e Ambientale, Università di Perugia, Italy, and Centro di Eccellenza Materiali Innovativi e Nanostrutturati, Università di Perugia, Italy.
Hydroalcoholic extracts from wheat sprouts, white tea, Morinda citrifolia and fermented papaya were analysed to determine their reducing power and antioxidant activity. The results show that the micromoles of potassium ferricyanide reduced by a quantity of extract corresponding to 1 g of the various dehydrated starting tissues are: 12.91+/-0.83 (wheat sprouts), 10.66+/-1.22 (M. citrifolia), 17.06+/-1.24 (white tea), and 1.05+/-0.09 (fermented papaya). In addition the results show a strong oxygen superoxide scavenging activity in the extracts from white tea, M. citrifolia and wheat sprouts. The activity of the fermented papaya extract is the lowest. The thin-layer chromatography and UV spectrophotometry of the extracts show in each source a mixture of antioxidant compounds probably belonging to the families of reducing glycosides and polyphenols. The chromatographic pattern of the antioxidant compounds and the UV spectrum are quite different in the various sources.
Bursill CA, Abbey M, Roach PD.
Wellcome Trust Centre of Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom; CSIRO, Health Sciences and Nutrition, Adelaide, SA 5000, Australia; University of Adelaide, SA 5000, Australia.
Tea in Lowering Cholesterol
Green tea extracts enriched in catechins decrease plasma cholesterol in hamsters, mice and rats. The aims of this study were to determine whether a catechin-enriched extract of green tea could lower plasma cholesterol in the cholesterol-fed rabbit and to determine the mechanism of action. Four groups of six New Zealand White rabbits were initially made hypercholesterolaemic by feeding a 0.25% (w/w) cholesterol diet for 2 weeks before the diet was supplemented with a catechin extract from green tea at 0, 0.5, 1 or 2% (w/w) for 4 weeks. Administration of the crude catechin extract from green tea significantly (p<0.05) lowered cholesterol in plasma (-60%), VLDL+IDL (-70%), LDL (-80%), liver (total by -25% and unesterified by -15%) and aorta (-25%) compared to control. There was a significant reduction in the cholesterol synthesis index (-60%) and a significant increase in hepatic LDL receptor activity (+80%) and protein (+70%) but there was no change in the intrinsic capacity to absorb cholesterol from the intestines. These results suggest that green tea catechins lowered plasma, liver and aortic cholesterol in the cholesterol-fed rabbit by lowering cholesterol synthesis and upregulating the hepatic LDL receptor.
Tijburg LB, Wiseman SA, Meijer GW, Weststrate JA.
Unilever Research Laboratorium, Vlaardingen, The Netherlands. Lilian.Tijburg@Unilever.com
The hypothesis that tea or dietary lipid-soluble antioxidants reduce atherogenesis by lowering the oxidizability of low-density lipoprotein (LDL) was investigated. Five groups of 20 female New Zealand white rabbits were fed a restricted amount of a high-fat (30 en%) semipurified diet supplemented with cholesterol (0.15%, w/w) for 21 weeks. The vitamin E content of the control diet was 40 mg/kg diet. The animals received either green tea or black tea in their drinking water or vitamin E (200 mg/kg diet) or beta-carotene (20 mg/kg). The serum cholesterol concentrations (in the order of 18-23 mmol/l) were not significantly different between the groups. Vitamin E was substantially increased as compared to controls in vitamin E supplemented animals (3-fold within 8 weeks in plasma and LDL; P < 0.01) and weakly (1.2-fold) by green and black tea (P < 0.05). Green tea consumption tended to reduce aortic lesion formation by 31% (24 +/- 3.2% versus 35 +/- 5.7% for control animals P = 0.11), while black tea, vitamin E and beta-carotene had no effect. This was in contrast to the resistance of isolated LDL to oxidation induced at high copper concentration. Green and black tea induced a 13% and 15% (P < 0.05) prolongation of the lag phase, respectively, with a correspondingly lower oxidation rate, while vitamin E increased the lag phase by 63% (P < 0.01) with a concomitant diminution of the oxidation rate and beta-carotene had no effect. Regression analysis showed that there was no relationship between the extent of atherosclerosis and LDL oxidizability or plasma malondialdehyde as marker of in vivo lipid peroxidation. The results of the present study raise the question whether LDL oxidizability (at least when tested at high induction rate ex vivo) is a primary causal mechanism in atherosclerosis in the cholesterol-fed rabbit. The suitability of the cholesterol-fed rabbit with extreme hypercholesterolaemia as a model to study antiatherosclerotic properties of dietary antioxidants, such as the tested polyphenols, is discussed.
Bursill C, Roach PD, Bottema CD, Pal S.
CSIRO Health Sciences and Nutrition, Adelaide, SA 5000, Australia.
Green tea from Camellia sinensis lowers plasma cholesterol in animal models of hypercholesterolemia. The aim of this study was to determine the effects of green tea on the expression of the hepatic low-density lipoprotein (LDL) receptor, a cell surface protein involved in the control of plasma cholesterol. Incubating human HepG2 liver cells in culture with green tea increased both LDL receptor binding activity and protein. An ethyl acetate extract of green tea, containing 70% (w/w) catechins, also increased the LDL receptor binding activity, protein, and mRNA, indicating that (1) the effect was at the level of gene transcription and that (2) the catechins were the active constituents. The mechanism by which green tea up-regulated the LDL receptor was then investigated. Green tea decreased the cell cholesterol concentration (-30%) and increased the conversion of the sterol-regulated element binding protein (SREBP-1) from the inactive precursor form to the active transcription-factor form. Consistent with this, the mRNA of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis, was also increased by green tea. In conclusion, green tea up-regulated the LDL receptor in HepG2 cells. The effect was most likely mediated through SREBP-1 in response to a decrease in the intracellular cholesterol concentration. The LDL receptor may therefore play a role in the hypocholesterolemic effect of green tea in vivo.
Preventive effects of green tea extract on lipid abnormalities in serum, liver and aorta of mice fed a atherogenic diet
Yamaguchi Y, Hayashi M, Yamazoe H, Kunitomo M.
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya, Japan.
This study examined the preventive effects of green tea extract on hyperlipidemia and lipid accumulation in the liver and aorta of mice fed an atherogenic diet enriched with 1.5% cholesterol, 0.5% cholic acid and 5% linoleic acid for a period of 14 weeks. The animals were given green tea extract in drinking water at doses of 50, 100 and 200 mg/kg/day. Treatment with green tea extract prevented the increase of serum cholesterol induced by the atherogenic diet 6 weeks after the start of the experiment. The increase of serum lipid peroxides was markedly prevented in a dose-related manner. The green tea extract also tended to prevent the increase of serum phospholipid and the decline of lecithin: cholesterol acyltransferase, but could not prevent decreases in serum triglycerides and high-density lipoprotein cholesterol. As for liver cholesterol, its content, particularly free cholesterol, in mice fed the atherogenic diet could be prevented from increasing by treatment with the extract at 50 and 100 mg/kg/day. In addition, the increase of aortic cholesterol, particularly esterified cholesterol, could be prevented in a dose-related manner. These results suggest that green tea has anti-atherosclerotic activity.
In vitro and in vivo antimicrobial action of tea: the commonest beverage of Asia
Bandyopadhyay D, Chatterjee TK, Dasgupta A, Lourduraja J, Dastidar SG.
Department of Pharmaceutical Technology, Jadavpur University, Calcutta, India.
The methanolic extract of leaves of Camellia sinensis (L) O. KUNTZE was screened for antimicrobial property against 111 bacteria comprising 2 genera of Gram positive and 7 genera of Gram negative bacteria. Most of these strains were inhibited by the compound at 10-50 microg/ml level and few strains were sensitive even at lower concentrations (5 microg/ml). The bacteria could be arranged in the decreasing order of sensitivity towards the compound in the following manner: Staphylococcus aureus, Vibrio cholerae, Escherichia coli, Shigella spp., Salmonella spp., Bacillus spp., Klebsiella spp. and Pseudomonas aeruginosa. The antibacterial activity of compound could also be confirmed in vivo. When it was given to Swiss strain of white mice at different dosages (30, 60 microg/mouse), it could significantly protect the animals challenged with 50 MLD of Salmonella typhimurium NCTC 74. According to Chi square test the in vivo data were highly significant (p<0.001).
Tea enhances insulin activity
Anderson RA, Polansky MM.
Nutrient Requirements and Functions Laboratory, Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Beltsville, Maryland 20705, USA.
The most widely known health benefits of tea relate to the polyphenols as the principal active ingredients in protection against oxidative damage and in antibacterial, antiviral, anticarcinogenic, and antimutagenic activities, but polyphenols in tea may also increase insulin activity. The objective of this study was to determine the insulin-enhancing properties of tea and its components. Tea, as normally consumed, was shown to increase insulin activity >15-fold in vitro in an epididymal fat cell assay. Black, green, and oolong teas but not herbal teas, which are not teas in the traditional sense because they do not contain leaves of Camellia senensis, were all shown to increase insulin activity. High-performance liquid chromatography fractionation of tea extracts utilizing a Waters SymmetryPrep C18 column showed that the majority of the insulin-potentiating activity for green and oolong teas was due to epigallocatechin gallate. For black tea, the activity was present in several regions of the chromatogram corresponding to, in addition to epigallocatechin gallate, tannins, theaflavins, and other undefined compounds. Several known compounds found in tea were shown to enhance insulin with the greatest activity due to epigallocatechin gallate followed by epicatechin gallate, tannins, and theaflavins. Caffeine, catechin, and epicatechin displayed insignificant insulin-enhancing activities. Addition of lemon to the tea did not affect the insulin-potentiating activity. Addition of 5 g of 2% milk per cup decreased the insulin-potentiating activity one-third, and addition of 50 g of milk per cup decreased the insulin-potentiating activity approximately 90%. Nondairy creamers and soy milk also decreased the insulin-enhancing activity. These data demonstrate that tea contains in vitro insulin-enhancing activity and the predominant active ingredient is epigallocatechin gallate.
Green tea
Tea is one of the most widely consumed beverages in the world today, second only to water, and its medicinal properties have been widely explored. The tea plant, Camellia sinensis, is a member of the Theaceae family, and black, oolong, and green tea are produced from its leaves. It is an evergreen shrub or tree and can grow to heights of 30 feet, but is usually pruned to 2-5 feet for cultivation. The leaves are dark green, alternate and oval, with serrated edges, and the blossoms are white, fragrant, and appear in clusters or singly. Unlike black and oolong tea, green tea production does not involve oxidation of young tea leaves. Green tea is produced from steaming fresh leaves at high temperatures, thereby inactivating the oxidizing enzymes and leaving the polyphenol content intact. The polyphenols found in tea are more commonly known as flavonols or catechins and comprise 30-40 percent of the extractable solids of dried green tea leaves. The main catechins in green tea are epicatechin, epicatechin-3-gallate, epigallocatechin, and epigallocatechin-3-gallate (EGCG), with the latter being the highest in concentration. Green tea polyphenols have demonstrated significant antioxidant, anticarcinogenic, anti-inflammatory, thermogenic, probiotic, and antimicrobial properties in numerous human, animal, and in vitro studies.
Factors affecting the levels of tea polyphenols and caffeine in tea leaves
Lin YS, Tsai YJ, Tsay JS, Lin JK.
Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
An isocratic HPLC procedure was developed for the simultaneous determination of caffeine and six catechins in tea samples. When 31 commercial teas extracted by boiling water or 75% ethanol were analyzed by HPLC, the levels of (-)-epigallocatechin 3-gallate (EGCG), and total catechins in teas were in the order green tea (old leaves) > green tea (young leaves) and oolong tea > black tea and pu-erh tea. Tea samples extracted by 75% ethanol could yield higher levels of EGCG and total catechins. The contents of caffeine and catechins also have been measured in fresh tea leaves from the Tea Experiment Station in Wen-Shan or Taitung; the old tea leaves contain less caffeine but more EGCG and total catechins than young ones. To compare caffeine and catechins in the same tea but manufactured by different fermentation processes, the level of caffeine in different manufactured teas was in the order black tea > oolong tea > green tea > fresh tea leaf, but the levels of EGCG and total catechins were in the order green tea > oolong tea > fresh tea leaf > black tea. In addition, six commercial tea extracts were used to test the biological functions including hydroxyl radical scavenging, nitric oxide suppressing, and apoptotic effects. The pu-erh tea extracts protected the plasmid DNA from damage by the Fenton reaction as well as the control at a concentration of 100 microg/mL. The nitric oxide suppressing effect of tea extracts was in the order pu-erh tea >/= black tea > green tea > oolong tea. The induction of apoptosis by tea extract has been demonstrated by DNA fragmentation ladder and flow cytometry. It appeared that the ability of tea extracts to induce HL-60 cells apoptosis was in the order green tea > oolong > black tea > pu-erh tea. All tea extracts extracted by 75% ethanol have stronger biological functions than those extracted by boiling water.
The effect of tea consumption on oxidative stress in smokers and nonsmokers
Klaunig JE, Xu Y, Han C, Kamendulis LM, Chen J, Heiser C, Gordon MS, Mohler ER.
Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
While the anticarcinogenic effects of tea in animal models have been reported by several groups, human epidemiological studies examining tea consumption and cancer prevention have produced equivocal results. The beneficial properties of tea to human health may be related to the antioxidant properties of tea components. However, little evidence has been provided that tea consumption can either increase the antioxidant capacity or decrease oxidative stress in humans. In the present study, the effects of tea treatment (green tea) on biomarkers of oxidative stress were investigated in smokers and nonsmokers in two volunteer study groups (one in China and the other in United States). Green tea consumption in both study groups decreased oxidative DNA damage (8-OHdG in white blood cells and urine), lipid peroxidation (MDA in urine), and free radical generation (2, 3-DHBA in urine) in smokers. Nonsmokers (US study group) also exhibited a decrease in overall oxidative stress.
The antioxidative property of green tea against iron-induced oxidative stress in rat brain
Lin AM, Chyi BY, Wu LY, Hwang LS, Ho LT.
Department of Medical Research and Education, Veterans General Hospital-Taipei, Taiwan.
The antioxidative property of green tea against iron-induced oxidative stress was investigated in the rat brain both in vivo and in vivo. Incubation of brain homogenates at 37 degrees C for 4 hours in vitro increased the formation of Schiff base fluorescent products of malonaldehyde, an indicator of lipid peroxidation. Auto-oxidation (without exogenous iron) of brain homogenates was inhibited by green tea extract in a concentration-dependent manner. Moreover, incubation with iron (1 microM) elevated lipid peroxidation of brain homogenates after 4-hour incubation at 37 degrees C. Co-incubation with green tea extract dose-dependently inhibited the iron-induced elevation in lipid peroxidation. For the in vivo studies: ferrous citrate (iron, 4.2 nmoles) was infused intranigrally and induced degeneration of the nigrostriatal dopaminergic system of rat brain. An increase in lipid peroxidation in substantia nigra as well as a decrease in dopamine content in striatum was observed seven days after the iron infusion. Intranigral infusion of green tea extract alone did not increase, and in some cases, even decreased lipid peroxidation in substantia nigra. Co-infusion of green tea extract prevented oxidative injury induced by iron. Both iron-induced elevation in lipid peroxidation in substantia nigra and iron-induced decrease in dopamine content in striatum were suppressed. Oral administration of green tea extract for two weeks did not prevent the iron-induced oxidative injury in nigrostriatal dopaminergic system. Our results suggest that intranigral infusion of green tea extract appears to be nontoxic to the nigrostriatal dopaminergic system. Furthermore, the potent antioxidative action of green tea extract protects the nigrostriatal dopaminergic system from the iron-induced oxidative injury.
Effect of green tea and black tea on the metabolisms of mineral elements in old rats
Zeyuan D, Bingying T, Xiaolin L, Jinming H, Yifeng C.
Institute of Food Nutrition, Nanchang University, China.
A 2-mo experiment with the white Sprague-Dawley (SD) rats was conducted to investigate the effect of the water extracts of black tea (BTWE) and green tea (GTWE) and the black tea leaves (BTF) and the green tea leaves (GTF) on the metabolism of mineral elements. One hundred eight 12-mo-old white SD rats were randomly divided into 13 groups; 6 of these drank the BTWE or GTWE in which the water extracts concentrations of black tea or green tea were, respectively, 0.6%, 1.2%, and 2.4%, and 6 of these had black tea leaves (BTF) and green tea leaves (GTF) added in which the contents of BTF or GTF were, respectively, 0.5%, 1.0%, and 2.0%, one of these was control. The teas and their water extracts could promote the absorption of manganese and copper. In GTF, BTF, GTWE, and BTWE, the apparent absorption rates of manganese were significantly increased. The manganese contents in the tibia were also elevated, and the differences between GTWE and GTF were significant. The apparent absorption rates of copper and the copper contents in the tibia were increased, but not significantly. The teas and their water extracts inhibited the absorption of calcium (p > 0.05) and iron (p < 0.05). The cerebrum calcium contents were significantly decreased, but the contents of calcium and iron in tibia were not significantly changed. Compared with the control, although the apparent absorption rates of aluminum in all experimental groups were not observed to be different, the aluminum contents in the tibia (p > 0.05) and cerebrum (p < 0.05) were increased. GTF and GTWE decreased the apparent absorption rates of zinc, but BTF and BTWE increased them; the zinc contents in tibia were a little improved, whereas its contents in the cerebrum were gradually decreased with the increase of tea leaves dose and tea concentration.
Black tea, green tea, and tea polyphenols. Effects on trace element status in weanling rats
Record IR, McInerney JK, Dreosti IE.
CSIRO Division of Human Nutrition, Adelaide, S Australia.
Previous studies have shown that tea consumption can impair trace element metabolism, particularly iron status, and increase the risk of anemia in humans and animals. More recently, however, evidence has been accumulating to show that, in animals, consumption of green tea or its polyphenols is associated with a reduction of the incidence and severity of a variety of experimentally induced cancers. In this study we have monitored the growth, trace element status, including hematological parameters of weanling rats given either (1) water, (2) 1% black tea, (3) 1% green tea, or (4) 0.2% crude green tea extract as their sole drinking fluid while consuming diets containing either adequate or low amounts of iron. With the exception of manganese, none of the trace elements studied (iron, copper, zinc, and manganese) or the hematological indices measured were affected by the type of beverage supplied, even though the polyphenol extract was shown to chelate metals in vitro and all the animals fed the low iron diet were shown to be anemic. There appeared to be an effect of black and green teas on manganese balance in both the first and last weeks of the study. A lower level of brain manganese was associated with green tea consumption, and a higher level of this element in the kidneys of animals fed black tea. The results demonstrate that both black and green teas and a green tea polyphenol extract do not represent a risk to animals consuming the beverages as their sole fluid intake with respect to iron availability, although the interactions with manganese deserve further study.
Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement
Henning SM, Niu Y, Lee NH, Thames GD, Minutti RR, Wang H, Go VL, Heber D.
Center for Human Nutrition, David Geffen School of Medicine and the Department of Biostatistics, School of Public Health, University of California, Los Angeles, 90095, USA. shenning@mednet.ucla.edu
BACKGROUND: Green and black tea polyphenols have been extensively studied as cancer chemopreventive agents. Many in vitro experiments have supported their strong antioxidant activity. Additional in vivo studies are needed to examine the pharmacokinetic relation of absorption and antioxidant activity of tea polyphenols administered in the form of green or black tea or tea extract supplements. OBJECTIVE: The purpose of this study was to compare the pharmacokinetic disposition of tea polyphenols and their effect on the antioxidant capacity in plasma 8 h after a bolus consumption of either green tea, black tea, or a green tea extract supplement. DESIGN: Thirty healthy subjects were randomly assigned to 3 different sequences of green tea, black tea, or a green tea extract supplement in a 3 x 3 crossover design with a 1-wk washout period in between treatments. RESULTS: Flavanol absorption was enhanced when tea polyphenols were administered as a green tea supplement in capsule form and led to a small but significant increase in plasma antioxidant activity compared with when tea polyphenols were consumed as black tea or green tea. All 3 interventions provided similar amounts of (-)-epigallocatechin-3-gallate. CONCLUSIONS: Our observations suggest that green tea extract supplements retain the beneficial effects of green and black tea and may be used in future chemoprevention studies to provide a large dose of tea polyphenols without the side effects of caffeine associated with green and black tea beverages.
Antioxidative activity of green tea polyphenol in cholesterol-fed rats
Yokozawa T, Nakagawa T, Kitani K.
Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan. yokozawa@ms.toyoma-mpu.ac.jp
This study investigated the effects of green tea polyphenol on the serum antioxidative activity and cholesterol levels of cholesterol-fed rats and compared them with those of probucol, an antioxidant hypocholesterolemic agent. To evaluate the antioxidative activity, the susceptibility to oxidative modification of low-density lipoprotein (LDL) isolated from the serum of cholesterol-fed rats was measured, as was the serum antioxidative activity using the spontaneous autoxidation system of brain homogenate. Administration of green tea polyphenol effectively inhibited LDL oxidation and elevated serum antioxidative activity to the same degree as probucol. However, higher amounts of polyphenol than probucol needed to be administered to reduce the total, free, and LDL cholesterol levels. Furthermore, green tea polyphenol increased the levels of high-density lipoprotein (HDL) cholesterol, leading to dose-dependent improvement of the atherogenic index, an effect that was not seen with probucol. Thus, green tea polyphenol may exert an antiatherosclerotic action by virtue of its antioxidant properties and by increasing HDL cholesterol levels.
Green, oolong and black tea extracts modulate lipid metabolism in hyperlipidemia rats fed high-sucrose diet.
Yang M, Wang C, Chen H.
Department of Food and Nutrition, Hung Kuang Institute of Technology Shalu, Taichung 433, Taiwan, People's Republic of China
The main goal of this study was to compare effects of ethanol-soluble fractions prepared from various types of teas on sucrose-induced hyperlipidemia in 5-week old male Sprague-Dawley rats. Rats (n = 6-8 per group) weighed approximately 200 g were randomly divided into control diet, sucrose-rich diet, green tea, oolong tea and black tea groups. Control-diet group was provided with modified AIN-93 diet while the others consumed sucrose-rich diet. Tea extracts (1% w/v) were supplied in the drink for green tea, oolong tea and black tea groups. Results indicated sucrose-rich diet induced hypertriglyceridemia and hypercholesterolemia. Food intake was reduced by oolong tea extract. Consuming oolong and black tea extracts also significantly decreased body weight gains and food efficiency. Hypertriglyceridemia was normalized by green and black tea drink on day 18 and by oolong tea extract on day 25, respectively. Hypercholesterolemia was normalized by green tea on day 18 and by oolong tea and black tea on day 25, respectively. Plasma HDL-cholesterol concentrations were not affected by any tea extract. The triglyeride content in the liver as well as the cholesterol content in the heart of rats fed sucrose-rich diet were elevated and were normalized by all types of tea drink tested. Although green and oolong tea extracts contained similar composition of catechin, our findings suggest green tea exerted greater antihyperlipidemic effect than oolong tea. Apparent fat absorption may be one of the mechanisms by which green tea reduced hyperlipidemia as well as fat storage in the liver and heart of rats consumed sucrose-rich diet.
Anti-obesity action of oolong tea
Han LK, Takaku T, Li J, Kimura Y, Okuda H.
2nd Department of Medical Biochemistry, School of Medicine, Ehime University, Japan.
OBJECTIVE: Oolong tea is traditionally reported to have anti-obesity and hypolipidaemic effects. The present study was performed to clarify whether oolong tea prevented obesity induced in mice by the oral administration of a high-fat diet for 10 weeks. DESIGN: High-fat diet-induced obese mice were treated with oolong tea for 10 weeks. The effects of various active fractions isolated from oolong tea on noradrenaline-induced lipolysis were examined with isolated fat cells and a cell-free system consisting of lipid droplets and hormone-sensitive lipase (HSL). RESULTS: The mean food consumption was not significantly different between high-fat diet-treated mice and high-fat plus oolong tea diet-treated mice. Oolong tea prevented the obesity and fatty liver induced by a high-fat diet. A water extract of oolong tea enhanced noradrenaline-induced lipolysis, and the active substance was identified as caffeine. Caffeine enhanced noradrenaline-induced lipolysis in fat cells without a concomitant increase in HSL activity and also accelerated the hormone-induced lipolysis in a cell-free system consisting of lipid droplets and HSL, but not in the cell-free system with sonicated lipid droplets and HSL. Oolong tea extract inhibited pancreatic lipase activity. CONCLUSION: It was demonstrated that the anti-obesity effects of oolong tea in high-fat diet-treated mice might be due partly to the enhancing effect of caffeine isolated from oolong tea on noradrenaline-induced lipolysis in adipose tissue, and to the inhibitory action of some other substance in oolong tea on pancreatic lipase activity. Caffeine was found to enhance lipolysis through acting on lipid droplets but not on HSL. The results suggest that oolong tea may be an effective crude drug for the treatment of obesity and fatty liver caused by a high-fat diet.
Anti-human immunodeficiency virus activity of oligosaccharides from rooibos tea (Aspalathus linearis) extracts in vitro
Nakano M, Nakashima H, Itoh Y.
Institute for Medical Science of Aging, Aichi Medical University, Japan.
The active substances, acid polysaccharides, were extracted with 1% sodium hydroxide from the leaves of rooibos tea (Aspalathus linearis), Du Zhong Cha (Eucommia ulmoides Oliv.) and Japanese tea leaves (Camellia sinensis var. sinensis). The alkaline extracts of Rooibos tea and Du-Zhong tea leaves, but not Japanese tea leaves suppressed the HIV-induced cytopathicity using HIV (HTLV-III) infected MT-4 cells, having extremely low cytotoxicity: Its 50% effective concentration (EC50) was 12-67 micrograms/mL, white 50% cytotoxic concentration (CC50) was higher than 1.0 mg/mL. The active substances were purified with ethanol precipitation. The substances were composed of 27% of reducing sugar, 46% of neutral sugars and 22% of uronic acid. A LD50 of the alkaline extracts from rooibos tea was higher than 1.2 g/kg body weight. Acid degradated substances composed of disaccharides and trisaccharides, were also suppressed the HIV-induced cytopathicity. From these results, it is probable that acid polysaccharides from rooibos tea were extremely safe, and that HIV infection may be suppressed by daily intake of the alkaline extracts of rooibos tea and Du-Zhong tea.
Suppression of postprandial hypertriglyceridemia in rats and mice by oolong tea polymerized polyphenols
Toyoda-Ono Y, Yoshimura M, Nakai M, Fukui Y, Asami S, Shibata H, Kiso Y, Ikeda I.
Suntory Institute for Health Care Science, Osaka, Japan. yoshiko_toyoda@suntory.co.jp
Oolong tea-polymerized polyphenols (OTPP) are characterized polyphenols produced from semi-fermented tea (oolong tea). In the present study, we evaluated the suppressive effects of oolong tea extract and OTPP on postprandial hypertriglyceridemia in rats and mice. Lymphatic recovery of triglycerides in rats cannulated in the thoracic duct was delayed by the administration of oolong tea extract at 100 and 200 mg per head, and more effectively than with green tea extract. OTPP delayed lymphatic triglyceride absorption at 20 mg/head, though (-)-epigallocatechin gallate (EGCG) did not do so at the same dose. OTPP also suppressed postprandial hypertriglyceridemia after administration of olive oil in mice. The area under the curve (AUC) of plasma triglycerides was significantly decreased, by 53% and 76%, in the 500 and 1,000 mg/kg OTPP groups respectively, as compared with the control group. These results suggest that OTPP is responsible for the suppression of hypertriglyceridemia by ingestion of oolong tea.
Comparison of the antioxidant activity of roasted tea with green, oolong, and black teas
Satoh E, Tohyama N, Nishimura M.
Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan. es@obihiro.ac.jp
Although the antioxidant properties of green, oolong, and black teas have been well studied, antioxidant activity has not been examined in roasted tea. Therefore, in the current studies, we investigated the antioxidant activity of roasted tea in comparison with those of green, oolong, and black teas. Using water extracts of the various teas, we examined the total phenolic content as well as the antioxidant activities, including the reducing power, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and the inhibition of hemolysis caused by 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced lipid oxidation in erythrocyte membranes. The roasted tea contained lower levels of total phenolics than green, oolong, or black tea (green tea > oolong tea > black tea > roasted tea). The relative reducing power and DPPH scavenging activity decreased in the following order: green tea > roasted tea > oolong tea > black tea. Also, green tea was more effective against AAPH-induced erythrocyte hemolysis than other teas (green tea>roasted tea = oolong tea = black tea). These results suggest that roasted tea is beneficial to health, in humans, because of its high antioxidant activity.
Beneficial effects of green tea--a review
Cabrera C, Artacho R, Giménez R.
Departamento de Nutrición y Bromatología, Facultad de Farmacia, Campus Universitario de Granada, Granada, Spain. carmenc@ugr.es
Tea is the most consumed drink in the world after water. Green tea is a 'non-fermented' tea, and contains more catechins, than black tea or oolong tea. Catechins are in vitro and in vivo strong antioxidants. In addition, its content of certain minerals and vitamins increases the antioxidant potential of this type of tea. Since ancient times, green tea has been considered by the traditional Chinese medicine as a healthful beverage. Recent human studies suggest that green tea may contribute to a reduction in the risk of cardiovascular disease and some forms of cancer, as well as to the promotion of oral health and other physiological functions such as anti-hypertensive effect, body weight control, antibacterial and antivirasic activity, solar ultraviolet protection, bone mineral density increase, anti-fibrotic properties, and neuroprotective power. Increasing interest in its health benefits has led to the inclusion of green tea in the group of beverages with functional properties. However, although all the evidence from research on green tea is very promising, future studies are necessary to fully understand its contributions to human health, and advise its regular consumption in Western diets, in which green tea consumption is nowadays limited and sporadic.
Mechanisms of hypolipidemic and anti-obesity effects of tea and tea polyphenols
Lin JK, Lin-Shiau SY.
Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan. jklin@ha.mc.ntu.edu.tw
Among the health-promoting effects of tea and tea polyphenols, the cancer-chemopreventive effects in various animal model systems have been intensively investigated; meanwhile, the hypolipidemic and antiobesity effects in animals and humans have also become a hot issue for molecular nutrition and food research. It has been demonstrated that the body weights of rats and their plasma triglyceride, cholesterol, and LDL-cholesterol have been significantly reduced by feedings of oolong, black, pu-erh, and green tea leaves to the animals. It has been suggested that the inhibition of growth and suppression of lipogenesis in MCF-7 breast cancer cells may be through down-regulation of fatty acid synthase gene expression in the nucleus and stimulation of cell energy expenditure in the mitochondria. The experimental data indicated that the molecular mechanisms of fatty acid synthase gene suppression by tea polyphenols (EGCG, theaflavins) may invite down-regulation of EGFR/PI3K/Akt/Sp-1 signal transduction pathways.
Comparative studies on the hypolipidemic and growth suppressive effects of oolong, black, pu-erh, and green tea leaves in rats
Kuo KL, Weng MS, Chiang CT, Tsai YJ, Lin-Shiau SY, Lin JK.
Wun-Shan Branch, Tea Research and Extension Station, Taipei, Taiwan.
The four major commercial teas, oolong, black, pu-erh, and green teas, have been manufactured in southeast Asia. In this study, we evaluated the growth suppressive and hypolipidemic effect of these four different tea leaves by oral feeding to male Sprague-Dawley rats for 30 weeks. The results showed that the suppression of body weights of tea leaves-fed groups were in the order: oolong tea > pu-erh tea > black tea > green tea. Pu-erh tea and oolong tea could lower the levels of triglyceride more significantly than that of green tea and black tea, but pu-erh tea and green tea were more efficient than oolong tea and black tea in lowering the level of total cholesterol. In lipoprotein, 4% pu-erh tea could increase the level of HDL-C and decrease the level of LDL-C, but other teas simply decrease the levels of both. The activity of antioxidant enzyme SOD is increased in all tea-fed groups as compared to the basal diet-fed group. Finally, relative weight ratios of liver to epididylmal adipose tissue were lower in feeding oolong tea and pu-erh tea groups. On the basis of these findings, it seemed that the fully fermented pu-erh and black tea leaves and partially fermented oolong tea leaves were more effective on their growth suppressive and hypolipidemic effects as compared to the nonfermented green tea leaves.
Fragrances in oolong tea that enhance the response of GABAA receptors
Hossain SJ, Aoshima H, Koda H, Kiso Y.
Department of Physics, Biology and Informatics, Faculty of Science, Yamaguchi University, Yoshida, Japan.
We electrophysiologically investigated the effect of some fragrant compounds in oolong tea on the response of ionotropic gamma-aminobutyric acid (GABA) receptors (GABAA receptors) which were expressed in Xenopus oocytes. Of the tested fragrances in oolong tea, cis-jasmone, jasmine lactone, linalool oxide and methyl jasmonate significantly potentiated the response. Among these, cis-jasmone and methyl jasmonate potently potentiated the response, having a respective dissociation constant of the compound (Kp) and maximum potentiation (Vm) of 0.49 mM and 322% for cis-jasmone, and 0.84 mM and 450% for methyl jasmonate. Inhalation of 0.1% cis-jasmone or methyl jasmonate significantly increased the sleeping time of mice induced by pentobarbital, suggesting that these fragrant compounds were absorbed by the brain and thereby potentiated the GABAA receptor response. Both of these compounds may therefore have a tranquillizing effect on the brain.
Oolong tea increases energy metabolism in Japanese females
Komatsu T, Nakamori M, Komatsu K, Hosoda K, Okamura M, Toyama K, Ishikura Y, Sakai T, Kunii D, Yamamoto S.
Department of Applied Nutrition, The University of Tokushima School of Medicine, Tokushima, Japan.
Oolong tea is a traditional Chinese tea that has long been believed to be beneficial to health such as decreasing body fat. We were interested in this assertion and tried to evaluate the effect of oolong tea on energy expenditure (EE) in comparison with green tea. The subjects were eleven healthy Japanese females (age 20+/-1 y; body mass index (BMI) 21.2+/-2.5 kg/m2) who each consumed of three treatments in a crossover design: 1) water, 2) oolong tea, 3) green tea. Resting energy expenditure (REE) and EE after the consumption of the test beverage for 120 min were measured using an indirect calorimeter. The cumulative increases of EE for 120 min were significantly increased 10% and 4% after the consumption of oolong tea and green tea, respectively. EE at 60 and 90 min were significantly higher after the consumption of oolong tea than that of water (P<0.05). In comparison with green tea, oolong tea contained approximately half the caffeine and epigallocatechin galate, while polymerized polyphenols were double. These results suggest that oolong tea increases EE by its polymerized polyphenols.
Antihyperglycemic effect of oolong tea in type 2 diabetes
Hosoda K, Wang MF, Liao ML, Chuang CK, Iha M, Clevidence B, Yamamoto S.
Research Center, Suntory, Osaka, Japan.
OBJECTIVE: To determine the efficacy of oolong tea for lowering plasma glucose in type 2 diabetic patients in Miaoli, Taiwan. RESEARCH DESIGN AND METHODS: A total of 20 free-living subjects who had type 2 diabetes and took hyperglycemic drugs as prescribed were enrolled in the present study. Subjects consumed oolong tea (1,500 ml) or water for 30 days each in a randomized crossover design. Tea was not consumed for 14 days prior to treatments. RESULTS: Relative to initial concentrations, oolong tea markedly lowered concentrations of plasma glucose (from 229 +/- 53.9 to 162.2 +/- 29.7 mg/dl, P < 0.001) and fructosamine (from 409.9 +/- 96.1 to 323.3 +/- 56.4 micromol/l, P < 0.01), whereas the water control group had not changed (208.7 +/- 61.0 vs. 232.3 +/- 63.1 mg/dl for glucose and from 368.4 +/- 85.0 to 340.0 +/- 76.1 micromol/l for fructosamine). CONCLUSIONS: Oolong tea may be an effective adjunct to oral hypoglycemic agents in the treatment of type 2 diabetes.
A trial of oolong tea in the management of recalcitrant atopic dermatitis.
Uehara M, Sugiura H, Sakurai K.
Department of Dermatology, Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu 520-2193, Japan.
BACKGROUND: Mild cases of atopic dermatitis (AD) generally improve with standard treatment. However, standard treatment fails many patients with recalcitrant AD skin lesions. Study results in animal models have demonstrated that the administration of tea (ie, green, black, or oolong) has suppressed type I and type IV allergic reactions. OBJECTIVE: To test the effectiveness of oolong tea in the treatment of recalcitrant AD. PATIENTS: Although 121 patients with recalcitrant AD were enrolled in the study, 118 patients completed the open study. METHODS: Patients were asked to maintain their dermatological treatment. However, they were also instructed to drink oolong tea made from a 10-g teabag placed in 1000 mL of boiling water and steeped for 5 minutes. This amount was then divided into 3 equal servings and 1 serving was drunk daily after 3 regular meals. Photographs of 2 or 3 representative lesion sites were taken at baseline and at 1 and 6 months and the severity of pruritus was assessed on a 6-point Lickert-like scale ranging from markedly improved (>50% improvement) to worsened. RESULTS: After 1 month of treatment 74 (63%) of the 118 patients showed marked to moderate improvement of their condition. The beneficial effect was first noticed after 1 or 2 weeks of treatment. A good response to treatment was still observed in 64 patients (54%) at 6 months. CONCLUSION: The therapeutic efficacy of oolong tea in recalcitrant AD may well be the result of the antiallergic properties of tea polyphenols.
Mechanisms of hypolipidemic and anti-obesity effects of tea and tea polyphenols
Lin JK, Lin-Shiau SY.
Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan. jklin@ha.mc.ntu.edu.tw
Among the health-promoting effects of tea and tea polyphenols, the cancer-chemopreventive effects in various animal model systems have been intensively investigated; meanwhile, the hypolipidemic and antiobesity effects in animals and humans have also become a hot issue for molecular nutrition and food research. It has been demonstrated that the body weights of rats and their plasma triglyceride, cholesterol, and LDL-cholesterol have been significantly reduced by feedings of oolong, black, pu-erh, and green tea leaves to the animals. It has been suggested that the inhibition of growth and suppression of lipogenesis in MCF-7 breast cancer cells may be through down-regulation of fatty acid synthase gene expression in the nucleus and stimulation of cell energy expenditure in the mitochondria. The experimental data indicated that the molecular mechanisms of fatty acid synthase gene suppression by tea polyphenols (EGCG, theaflavins) may invite down-regulation of EGFR/PI3K/Akt/Sp-1 signal transduction pathways.
In vitro chemopreventive activity of Camellia sinensis, Ilex paraguariensis and Ardisia compressa tea extracts and selected polyphenols
Ramirez-Mares MV, Chandra S, de Mejia EG.
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 228 ERML, MC-051, 1201 W. Gregory Drive, 61801, USA.
Several herbal teas contain bioactive compounds that have been associated with a lower risk of chronic diseases including cancer. The aim of this study was to evaluate the chemopreventive activity of tea aqueous extracts and selected constituent pure polyphenols using a battery of in vitro marker systems relevant for the prevention of cancer. The effects of (-) epigallocatechin gallate (EGCG), quercetin (Q), gallic acid (GA), green tea (GT, Camellia sinensis), ardisia tea (AT, Ardisia compressa) and mate tea (MT, Ilex paraguariensis) extracts were tested. Cytotoxicity, TPA-induced ornithine decarboxylase (ODC) and quinone reductase (QR) activities were evaluated in vitro using HepG2 cells. The topoisomerase inhibitory activity was also tested, using the Saccharomyces cerevisiae yeast system. Results suggest that MT, AT and GT are cytotoxic to the HepG2 cells, with MT demonstrating dominant cytotoxicity. EGCG showed greater cytotoxicity than Q and GA against HepG2 cells. The greatest inhibition (82%) of TPA-induced ODC activity was shown by Q, with 25 microM (IC50 = 11.90 microM). Topoisomerase II, but not topoisomerase I, was the cellular target of MT, AT, EGCG, Q and GA, which acted mainly as true catalytic inhibitors. The cytotoxic activity and the inhibition of topoisomerase II may contribute to the overall chemopreventive activity of AT and MT extracts. Ardisia and mate teas may thus share a public health potential as chemopreventive agents.
Antioxidant activity of a botanical extract preparation of Ilex paraguariensis: prevention of DNA double-strand breaks in Saccharomyces cerevisiae and human low-density lipoprotein oxidation.
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