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Coffee and tea consumption and the risk for subarachnoid hemorrhage: A meta-analysis.
Rui, Q, Ni, H, Liu, H, Zhu, X, Gao, R
Nutrition (Burbank, Los Angeles County, Calif.). 2019;:21-28
Abstract
OBJECTIVES Reports on the association between coffee or tea consumption and subarachnoid hemorrhage (SAH) risk are inconsistent. The aim of this study was to determine if an association exists between consumption of coffee or tea and the risk for SAH. METHODS A random-effects model was used to estimate the summary relative risks (RRs) and 95% confidence intervals (CIs). Heterogeneity among studies was assessed using the statistics Cochran's Q and I2. Seven studies on coffee consumption and five on tea consumption were included in the meta-analysis. RESULTS The pooled RRs of SAH for the highest versus the lowest categories of coffee and tea consumption were 1.31 (95% CI, 0.84-2.05) and 0.83 (95% CI, 0.65-1.08), respectively. There was evidence of heterogeneity among studies of coffee consumption (Pheterogeneity = 0.002, I2 = 71.7%) but not among studies of tea consumption (Pheterogeneity = 0.34, I2 = 11.3%). Omitting one study that substantially contributed to the heterogeneity among studies of coffee consumption yielded a pooled RR of 1.51 (95% CI, 1.10-2.06). Dose-response analysis showed that the summary RRs of SAH for an increase of one cup of coffee and tea consumption per day were 1.00 (95% CI, 0.96-1.04) and 0.97 (95% CI, 0.85-1.11), respectively. There was no evidence of publication bias. CONCLUSION Our meta-analysis of current evidence does not support an association between the consumption of coffee or tea and SAH risk. Further studies with prospective designs that control for important confounders and provide sufficient data for dose-response analysis are warranted.
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Targeting Bacterial Biofilms by the Green Tea Polyphenol EGCG.
Hengge, R
Molecules (Basel, Switzerland). 2019;(13)
Abstract
Bacterial biofilms are multicellular aggregates in which cells are embedded in an extracellular matrix of self-produced biopolymers. Being refractory to antibiotic treatment and host immune systems, biofilms are involved in most chronic infections, and anti-biofilm agents are being searched for urgently. Epigallocatechin-3-gallate (EGCG) was recently shown to act against biofilms by strongly interfering with the assembly of amyloid fibres and the production of phosphoethanolamin-modified cellulose fibrils. Mechanistically, this includes a direct inhibition of the fibre assembly, but also triggers a cell envelope stress response that down-regulates the synthesis of these widely occurring biofilm matrix polymers. Based on its anti-amyloidogenic properties, EGCG seems useful against biofilms involved in cariogenesis or chronic wound infection. However, EGCG seems inefficient against or may even sometimes promote biofilms which rely on other types of matrix polymers, suggesting that searching for 'magic bullet' anti-biofilm agents is an unrealistic goal. Combining molecular and ecophysiological aspects in this review also illustrates why plants control the formation of biofilms on their surfaces by producing anti-amyloidogenic compounds such as EGCG. These agents are not only helpful in combating certain biofilms in chronic infections but even seem effective against the toxic amyloids associated with neuropathological diseases.
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Anti-Cancer Effects of Green Tea Polyphenols Against Prostate Cancer.
Miyata, Y, Shida, Y, Hakariya, T, Sakai, H
Molecules (Basel, Switzerland). 2019;(1)
Abstract
Prostate cancer is the most common cancer among men. Green tea consumption is reported to play an important role in the prevention of carcinogenesis in many types of malignancies, including prostate cancer; however, epidemiological studies show conflicting results regarding these anti-cancer effects. In recent years, in addition to prevention, many investigators have shown the efficacy and safety of green tea polyphenols and combination therapies with green tea extracts and anti-cancer agents in in vivo and in vitro studies. Furthermore, numerous studies have revealed the molecular mechanisms of the anti-cancer effects of green tea extracts. We believe that improved understanding of the detailed pathological roles at the molecular level is important to evaluate the prevention and treatment of prostate cancer. Therefore, in this review, we present current knowledge regarding the anti-cancer effects of green tea extracts in the prevention and treatment of prostate cancer, with a particular focus on the molecular mechanisms of action, such as influencing tumor growth, apoptosis, androgen receptor signaling, cell cycle, and various malignant behaviors. Finally, the future direction for the use of green tea extracts as treatment strategies in patients with prostate cancer is introduced.
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Effects of medium-term green tea extract supplementation combined with CrossFit workout on blood antioxidant status and serum brain-derived neurotrophic factor in young men: a pilot study.
Sadowska-Krępa, E, Domaszewski, P, Pokora, I, Żebrowska, A, Gdańska, A, Podgórski, T
Journal of the International Society of Sports Nutrition. 2019;(1):13
Abstract
BACKGROUND Potential health benefits are attributed to the antioxidant properties of green tea polyphenolic compounds. The main aim of the study was to evaluate the effects of a six-week green tea extract (GTE) supplementation combined with CrossFit workout on blood antioxidant status and serum brain-derived neurotrophic factor (BDNF) in men. METHODS Sixteen young males involved in CrossFit training were randomized into two groups supplemented with GTE or placebo for six weeks. Each participant performed an exercise test for the evaluation of maximum oxygen uptake (VO2max) twice, i.e., before starting (1st trial) and after completing the supplementation combined with CrosFit workout (2nd trial). Venous blood samples were drawn at rest, immediately post-test and after one hour of recovery in order to estimate activities of antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx], reduced glutathione [GR]), non-enzymatic antioxidants (reduced glutathione [GSH], uric acid [UA], total phenolics), total antioxidant capacity (FRAP), lipid peroxidation products (TBARS), and BDNF. RESULTS Except for a significantly higher SOD activity and FRAP level recorded at rest and post-exercise in the 2nd trial compared to the corresponding values in the 1st trial, no significant differences were recorded among other assayed measures such as CAT, GPx, GR, GSH and BDNF. Moreover, a percentage increase in FRAP level was twice as high after six weeks' GTE consumption than after placebo. Regardless of the trial, an increase in plasma UA concentration and a decrease in plasma total phenolics level were observed after exercise test. Plasma TBARS concentrations were significantly higher in PLA group after six weeks' CrossFit training, while in GTE group they were slightly lower compared to the corresponding values in the 1st trial. Moreover, there was a significant inverse correlation between FRAP and TBARS in the GTE-supplemented group (r = - 0.40, p < 0.05). CONCLUSIONS A six weeks' consumption of GTE had marginal effect on aerobic capacity and serum BDNF level in CrossFit-trained men, but it caused a marked increase in the blood antioxidant capacity and a moderate attenuation of the training-induced lipid peroxidation.
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Enantiomeric Trimethylallantoin Monomers, Dimers, and Trimethyltriuret: Evidence for an Alternative Catabolic Pathway of Caffeine in Tea Plant.
Wang, W, Zhu, BY, Wang, P, Zhang, P, Deng, WW, Wu, FH, Ho, CT, Ling, TJ, Zhang, ZZ, Wan, XC, et al
Organic letters. 2019;(13):5147-5151
Abstract
Racemic trimethylallantoin monomer (1), mesomeric and racemic trimethylallantoin dimers (2 and 3), were isolated from tea. Two pairs of optically pure enantiomers (1a, 1b and 3a, 3b) were separated by chiral column from the two racemes (1 and 3). Their structures were elucidated by a combination of extensive spectroscopic techniques, single-crystal X-ray diffraction, and experimental and calculated electronic circular dichroism. A novel caffeine catabolic pathway was proposed based on the caffeine stable isotopic tracer experiments.
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High-resolution pure shift NMR spectroscopy offers better metabolite discrimination in food quality analysis.
Bo, Y, Feng, J, Xu, J, Huang, Y, Cai, H, Cui, X, Dong, J, Ding, S, Chen, Z
Food research international (Ottawa, Ont.). 2019;:108574
Abstract
PSYCHE homonuclear decoupling, a prominent pure shift NMR method, is successfully applied to adulteration discrimination of honey and geographical originality identification of tea. Effects of homonuclear couplings are efficiently suppressed, producing resolution-enhanced spectra. The pair wise honey and tea samples are well separated in OPLS-DA models with high predictability. Due to the well-resolved and accurate assignment of singlet resonances after decoupling, PSYCHE is advantageous in the identification of differential components and accurate quantification of compound concentrations presented by enhanced volcano and Beeswarm plots of honey samples, while the analysis of NOESY is easily interfered by overlapped resonances, which is further proved by the STOCSY analysis, displaying the spectral stability and reproducibility. Experimental results show that PSYCHE can improve the spectral resolution of natural complex products such as honey and tea and be combined with multivariate statistical analysis and serve as a supplementary technique to the standard methods, especially for samples systems composed by a few high-content compounds.
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Plant Resources, Chemical Constituents, and Bioactivities of Tea Plants from the Genus Camellia Section Thea.
Meng, XH, Li, N, Zhu, HT, Wang, D, Yang, CR, Zhang, YJ
Journal of agricultural and food chemistry. 2019;(19):5318-5349
Abstract
Tea, as one of the most popular beverages with various bioactivities, is commonly produced from the fresh leaves of two widely cultivated tea plants, Camellia sinensis and C. sinensis var. assamica. Both plants belong to the genus Camellia section Thea, which was considered to have 12 species and 6 varieties according to Min's taxonomic system. Most species, except the cultivated species, are known as wild tea plants and have been exploited and utilized to produce tea by the local people of its growing areas. Thus far, six species and varieties have been phytochemically studied, leading to the identification of 398 compounds, including hydrolyzable tannins, flavan-3-ols, flavonoids, terpenoids, alkaloids, and other phenolic and related compounds. Various beneficial health effects were reported for tea and its components, involving antioxidant, antitumor, antimutagenic, antidiabetic, hypolipidemic, anti-inflammatory, antimicrobial, antiviral, antifungal, neuroprotective, hepatoprotective, etc. In this review, the geographical distribution of tea plants and the chemical constituents (1-398) reported from the genus Camellia section Thea and some tea products (green, black, oolong, and pu-erh tea) that have ever been studied between 1970 and 2018 have been summarized, taking species as the main hint, and the main biological activities are also discussed.
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Comparative evaluation of effects of natural antioxidants on the shear bond strength of composite resin to bleached enamel.
Rana, R, Kaushik, M, Sharma, R, Reddy, P, Mehra, N
Indian journal of dental research : official publication of Indian Society for Dental Research. 2019;(1):112-116
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Abstract
CONTEXT The use of antioxidants immediately after bleaching showed increased bond strength. AIMS This study aimed to compare the effects of natural antioxidants on the shear bond strength of composite resin to bleached enamel. MATERIALS AND METHODS Fifty extracted single-rooted upper incisors were decoronated by sectioning the roots 2 mm below the cementoenamel junction, and then, crowns were embedded in autopolymerizing acrylic resin block (3.0 cm × 3.0 cm × 3.0 cm) with the labial surface exposed. They were randomly divided into five groups, depending on the type of antioxidant used (n = 10): (i) Group 1: control (no bleaching), (ii) Group 2: bleaching only, (iii) Group 3: bleaching + 10% sodium ascorbate (antioxidant), (iv) Group 4: bleaching + green tea, and (v) Group 5: bleaching + white tea. Labial surfaces of 40 teeth were bleached with 38% hydrogen peroxide for 20 min following manufacturer's instructions. After that, the experimental groups (Groups 3, 4, and 5) were treated with respective antioxidant solutions before composite restorations were done using a cylindrical plastic mold (3 mm × 5 mm). Shear bond strength of the specimens was tested under universal testing machine. STATISTICAL ANALYSIS Data were analyzed with ANOVA and Tukey's post hoc test. RESULTS There were statistically significant differences between shear bond strength of control groups (Groups 1 and 2) and experimental groups (P < 0.05), but no significant difference in bond strength was observed among the antioxidants used. CONCLUSION Application of antioxidants immediately after bleaching showed increased bond strength. Green tea and white tea extract can be used as alternative antioxidants in improving the bond strength of enamel.
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Green Tea Catechin Extract Supplementation Does Not Influence Circulating Sex Hormones and Insulin-Like Growth Factor Axis Proteins in a Randomized Controlled Trial of Postmenopausal Women at High Risk of Breast Cancer.
Samavat, H, Wu, AH, Ursin, G, Torkelson, CJ, Wang, R, Yu, MC, Yee, D, Kurzer, MS, Yuan, JM
The Journal of nutrition. 2019;(4):619-627
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Abstract
BACKGROUND Consumption of green tea has been associated with reduced risk of breast cancer. Hormonal modulation has been suggested as one of the potential underlying mechanisms; however, it has yet to be fully elucidated in large, long-term human clinical trials. OBJECTIVE We investigated the effects of decaffeinated green tea extract (GTE) on circulating sex hormones and insulin-like growth factor (IGF) proteins. METHODS We conducted a placebo-controlled double-blind randomized clinical trial recruiting from 8 clinical centers in Minnesota. Participants were 538 healthy postmenopausal women randomly assigned to the GTE group (463 completed the study; mean age = 60.0 y) and 537 to the placebo group (474 completed; mean age = 59.7 y). Women in the GTE group orally took 4 decaffeinated capsules containing 1315 mg total catechins including 843 mg epigallocatechin-3-gallate daily for 1 y, whereas women in the placebo group took similar capsules containing no tea catechins. Blood sex hormones (estrone, estradiol, androstenedione, testosterone, and sex hormone-binding globulin) and IGF proteins (IGF-1 and IGF binding protein-3) were quantified at baseline and months 6 (for IGF proteins only) and 12, and were assessed as secondary outcomes of the study using a mixed-effect repeated-measures ANOVA model. RESULTS Women in the GTE group had significantly higher blood total estradiol (16%; P = 0.02) and bioavailable estradiol (21%; P = 0.03) than in the placebo group at month 12. There was a statistically significant interaction between GTE supplementation and duration of treatment on estradiol and bioavailable estradiol (both Ps for interaction = 0.001). The catechol-O-methyltransferase genotype did not influence blood sex hormones before or after GTE supplementation. The circulating concentrations of IGF proteins were comparable between GTE and placebo groups at all 3 time points. CONCLUSION These results suggest that a 12-mo GTE supplementation significantly increases circulating estradiol concentrations in healthy postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00917735.
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The effect of green tea on inflammatory mediators: A systematic review and meta-analysis of randomized clinical trials.
Haghighatdoost, F, Hariri, M
Phytotherapy research : PTR. 2019;(9):2274-2287
Abstract
Catechin in green tea might be able to reduce inflammatory mediators; therefore, in this study, we aimed to indicate green tea effects on inflammatory mediators such as tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP), and interleukin-6 (IL-6). The advanced search methods of electronic databases were used to find randomized clinical trials that assessed green tea effect on inflammatory mediators among adult population. Google Scholar, PubMed/Medline, EMBASE, SCOPUS, and ISI Web of Science were searched until January 2019. Delphi checklist was used for assessing the quality of included articles. Mean changes in serum inflammatory biomarkers were calculated by subtracting endpoint values from the baseline in each study arm. Then the effect size for each selected study was estimated as the difference between mean changes in the intervention and control groups. We included 16 articles in our meta-analysis and 17 articles in systematic review. Our results indicated that green tea could not significantly decrease serum CRP levels and significantly increased IL-6 and significantly decreased TNF-α levels. In conclusion, green tea might not be able to change inflammatory mediators especially in diseases with low inflammation, but scientists who want to assess green tea effect on inflammatory mediators should perform their study on patients with high inflammation. Studies exclusive on male or female and considering nutrients intake as a confounding factor are a necessity.