Research Database

Author: S. Gomikawa and Y. Ishikawa

 

Get the whole article here

Author: Jin Tae Hong and Seung Rel Ryu and Hye Jin Kim and Jong Kwon Lee and Sun Hee Lee and Dai Byung Kim and Yeo Pyo Yun and Jong Hoon Ryu and Byung Mu Lee and Pu Young Kim

Eicosanoids accumulation and formation of oxygen free radicals have been implicated in the pathogenesis of ischemia/reperfusion brain injury. In the present study, we examined whether green tea extract protects against ischemia/reperfusion-induced brain injury by minimizing eicosanoid accumulation and oxygen radical-induced oxidative damage in the brain. Green tea extract (0.5%) was orally administered to Wistar rats for 3 weeks before induction of ischemia. Ischemia was induced by the occlusion of middle cerebral arteries for 60 min and reperfusion was achieved for 24 h. Infarction volume in the ipsilateral hemisphere of ischemia/reperfusion animals was 114 ± 16 mm3 in the 0.5% green tea pretreated animals compared to 180 ± 54 mm3 in left hemisphere of nontreated animals. Green tea extract (0.5%) also reduced ischemia/reperfusion-induced eicosanoid concentration: Leukotriene C4 (from 245 ± 51 to186 ± 22), prostoglandin E2 (from 306 ± 71 to 212 ± 43) and thromboxane A2 (327 ± 69 to 251 ± 87 ng/mg protein). Ischemia/reperfusion-induced increases of hydrogen peroxide level (from 688 ± 76 to 501 ± 99 nmole/mg protein), lipid peroxidation products (from 1010 ± 110 to 820 ± 70 nmole/mg protein) and 8-oxodG formation (from 1.3 ± 0.3 to 0.8 ± 0.2 ng/μg DNA, ×10−2) were also reduced. Moreover, 0.5% green tea extract also reduced the apoptotic cell number (from 44 ± 11 to 29 ± 1 in the striatum, and from 72 ± 11 to 42 ± 5 apoptotic cells/high power field in the cortex region). Green tea extract pretreatment also promoted recovery from the ischemia/reperfusion-induced inhibition of active avoidance. The present study shows that the minimizing effect of green tea extract on the eicosanoid accumulation and oxidative damage in addition to the reduction of neuronal cell death could eventually result in protective effect on the ischemia/reperfusion-induced brain injury and behavior deficit.

 

 

Get the whole article here

Author: Shizuka Sasazuki and Hiroko Kodama and Kouichi Yoshimasu and Ying Liu and Masakazu Washio and Keitaro Tanaka and Shoji Tokunaga and Suminori Kono and Hidekazu Arai and Yoshitaka Doi and Tomoki Kawano and Osamu Nakagaki and Kazuyuki Takada and Samon Koyanagi and Koji Hiyamuta and Takanobu Nii and Kazuyuki Shirai and Munehito Ideishi and Kikuo Arakawa and Masahiro Mohri and Akira Takeshita

PURPOSE: To examine the relation between green tea consumption and arteriographically determined coronary atherosclerosis. METHODS: Study subjects were 512 patients (302 men and 210 women) aged 30 years or older who underwent coronary arteriography for the first time at four hospitals in Fukuoka City or one hospital in an adjacent city between September 1996 and August 1997. Lifestyle characteristics including green tea consumption were ascertained before arteriography by a questionnaire supported with interview. RESULTS: 117 men (38.7%) and 50 women (23.8%) had significant stenosis of one or more coronary arteries. Green tea consumption tended to be inversely associated with coronary atherosclerosis in men, but not in women. An evident, protective association between green tea and coronary atherosclerosis was observed in a subgroup of 262 men excluding those under dietary or drug treatment for diabetes mellitus. In this subgroup, after adjustment for traditional coronary risk factors and coffee, odds ratios of significant stenosis for consumption of 2–3 cups and 4 or more cups per day were 0.5 (95% confidence interval 0.2–1.2) and 0.4 (0.2–0.9), respectively, as compared with a consumption of one cup per day or less. CONCLUSIONS: The results indicate that green tea may be protective against coronary atherosclerosis at least in men.

 

 

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: Segaran P. Pillai and Christine A. Pillai and Delbert M. Shankel and Lester A. Mitscher

Resistance to multiple antimicrobial agents has now become a prominent fact of contemporary life. It is believed that poor patient compliance, e.g. interrupted or premature cessation of therapy; and misuse or abuse of antibiotics, e.g. wrong antibiotic or insufficient dose, play important roles in resistance development. We present evidence that, this form of resistance often stems from spontaneous mutations accompanied by the positive selecting pressure of the doses of antibiotics being between the MIC and MBC levels. A number of antimutagenic agents, e.g. green tea catechins, and other antioxidants, etc. are able to suppress the emergence of resistance. In many cases, these agents are capable of exerting these effects at doses which by themselves produce no visible effect on growth. In a number of cases antimutagenic substances capable of preventing resistance emergence are present in normal food stuffs. These effects are exerted against resistance to tetracyclines, fluoroquinolones, macrolides, β-lactams, aminoglycosides and the like. The implications of these laboratory findings for practical chemotherapy are discussed.

 

 

Get the whole article here

Author: Ming-Hua Yang and Cheng-Hsin Wang and Hsiao-Ling Chen

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.

 

 

Get the whole article here

Author: Lynnette R. Ferguson

Polyphenols are a large and diverse class of compounds, many of which occur naturally in a range of food plants. The flavonoids are the largest and best-studied group of these. A range of plant polyphenols are either being actively developed or currently sold as dietary supplements and/or herbal remedies. Although, these compounds play no known role in nutrition (non-nutrients), many of them have properties including antioxidant, anti-mutagenic, anti-oestrogenic, anti-carcinogenic and anti-inflammatory effects that might potentially be beneficial in preventing disease and protecting the stability of the genome. However not all polyphenols and not all actions of individual polyphenols are necessarily beneficial. Some have mutagenic and/or pro-oxidant effects, as well as interfering with essential biochemical pathways including topoisomerase enzyme activities, prostanoid biosynthesis and signal transduction. There is a very large amount of in vitro data available, but far fewer animal studies, and these are not necessarily predictive of human effects because of differences in bacterial and hepatic metabolism of polyphenols between species. Epidemiological studies suggest that high green tea consumption in the Japanese population and moderate red wine consumption in the French population may be beneficial for heart disease and cancer, and these effects may relate to specific polyphenols. A small number of adequately controlled human intervention studies suggest that some, but not all polyphenol extracts or high polyphenol diets may lead to transitory changes in the antioxidative capacity of plasma in humans. However, none of these studies have adequately considered long-term effects on DNA or the chromosome and unequivocally associated these with polyphenol uptake. Furthermore, clinical trials have required intravenously administered polyphenols at concentrations around 1400 mg/m2 before effects are seen. These plasma concentrations are unlikely to be achieved using the dietary supplements currently available. More focused human studies are necessary before recommending specific polyphenolic supplements at specific doses in the human population.

 

 

Get the whole article here

Author: Craig A. Elmets and Divya Singh and Karen Tubesing and Mary Matsui and Santosh Katiyar and Hasan Mukhtar

Background: In animal models, extracts from green tea have been shown to be remarkably effective at reducing the severity of adverse human health effects of overexposure to ultraviolet (UV) radiation. Although sunscreens and other photoprotective measures have traditionally been used for this purpose, there is a need for additional measures and natural products are increasingly being explored for that purpose. Objective: Our purpose was to evaluate the effect of polyphenols from green tea on parameters associated with acute UV injury. Methods: Areas of skin of normal volunteers were treated with an extract of green tea or one of its constituents. Thirty minutes later, the treated sites were exposed to a 2 minimal erythema dose solar simulated radiation. UV-treated skin was examined clinically for UV-induced erythema, histologically for the presence of sunburn cells or Langerhans cell distributions, or biochemically for UV-induced DNA damage. Results: Application of green tea extracts resulted in a dose-dependent inhibition of the erythema response evoked by UV radiation. The (-)-epigallocatechin-3-gallate (EGCG) and (-)-epicatechin-3-gallate (ECG) polyphenolic fractions were most efficient at inhibiting erythema, whereas (-)-epigallocatechin (EGC) and (-)-epicatechin (EC) had little effect. On histologic examination, skin treated with green tea extracts reduced the number of sunburn cells and protected epidermal Langerhans cells from UV damage. Green tea extracts also reduced the DNA damage that formed after UV radiation. Conclusion:Polyphenolic extracts of green tea are effective chemopreventive agents for many of the adverse effects of sunlight on human health and may thus serve as natural alternatives for photoprotection. (J Am Acad Dermatol 2001;44:425-32)

 

Get the whole article here

Author: Jin Tae Hong and Seung Rel Ryu and Hye Jin Kim and Jong Kwon Lee and Sun Hee Lee and Yeo Pyo Yun and Byung Mu Lee and Pu Young Kim

Free radical-induced oxidative damages of macromolecules and cell death are important factors in the pathogenesis of ischemia/reperfusion brain injury. In the present study, an investigation as to whether green tea extract reduces ischemia/reperfusion-induced brain injury in Mongolian gerbils was conducted. The effect of green tea on the ischemia/reperfusion-induced production of hydrogen peroxide, lipid peroxidation and oxidative DNA damage (formation of 8-hydroxydeoxyguanosine), and cell death in addition to locomotor activity was studied. Two doses (0.5 or 2%) of green tea extract were added into the drinking water and to be accessed by animals ad libitum for 3 weeks prior to the induction of ischemia. A global ischemia was induced by the bilateral occlusion of the common carotid arteries for 5 min. Reperfusion was achieved by releasing the occlusion and restoring blood circulation for 48 h. The infarction volumes were 112±31 mm3 and 76±11 mm3 in the 0.5 and 2% green tea pretreated animals compared to 189±12 mm3 in the ischemia/reperfusion animals. Green tea extract also reduced the levels of ischemia/reperfusion-induced hydrogen peroxide (from 1470±170 to 1034±46 and 555±30 nmole/mg protein), lipid peroxidation products (from 1410±210 to 930±40 and 330±20 nmole/mg protein) and 8-oxodG (from 3.9±0.1 to 2.8±0.3 and1.9±0.3 ng/μg DNA, ×10−2) by pretreatment of 0.5 or 2% green tea for 3 weeks, respectively. Moreover, green tea also reduced the number of ischemia/reperfusion-induced apoptotic cells (from 59±12 to 37±8, 15±11 apoptotic cells/high power field in the striatum region) and locomotor activity (from 15140±2940 to 3900±600 and 4100±1200). This study therefore suggests that green tea may be a useful agent for the prevention of cerebral ischemia damage.

 

Get the whole article here

Author: Manami Inoue and Kazuo Tajima and Mitsuhiro Mizutani and Hiroji Iwata and Takuji Iwase and Shigeto Miura and Kaoru Hirose and Nobuyuki Hamajima and Suketami Tominaga

Experimental studies suggest various features of anticancer activity of green tea including inhibitory effect of tumor invasion and metastasis. This study was conducted to examine the association between regular green tea consumption prior to diagnosis and subsequent risk of breast cancer recurrence. The Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC) was started in 1988, in which information on lifestyle has routinely been collected from all first-visit outpatients by questionnaire. A total of 1160 new surgical cases of female invasive breast cancers with HERPACC information diagnosed between June 1990 and August 1998 were followed up through December 1999, and the risk (hazard ratio: HR) of recurrence was assessed with reference to daily green tea consumption using a Cox proportional hazard model. During 5264 person-years of follow-up, 133 subjects (12%) were documented to suffer recurrence of breast cancer. A decreased HR for recurrence adjusted for stage was observed with consumption of three or more daily cups of green tea (HR=0.69, 95% confidence interval (95%CI)=0.47–1.00). Particularly in stage I, the HR was decreased statistically significantly (HR=0.43, 95%CI=0.22–0.84). A similar tendency was observed for stage II subjects, but was not present among more advanced stages. Although careful interpretation is needed, these results suggest the possibility that regular green tea consumption may be preventive against recurrence of breast cancer in early stage cases.

 

 

Get the whole article here