Research Database

Author: I.M. Kapetanovic and J.A. Crowell and R. Krishnaraj and A. Zakharov and M. Lindeblad and A. Lyubimov

Standardized green tea extract was evaluated for exposure and toxicity in Beagle dogs following oral dosing by capsules. The main component (−)-epigallocatechin gallate (EGCG) accounted for 56–72% of the material. A 9-month chronic study (0, 200, 500, and 1000 mg/kg/day) was done in fasted dogs to take advantage of the reported improved catechin bioavailability with fasting. Extensive morbidity, mortality, and pathology of many major organs led to its early termination at 6.5 months and prevented identification of the toxicity mechanisms. A follow-up 13-week study examined the exposure to and toxicity of the extract. In general, toxicities were less severe than in the chronic study during the same interval. Dosing in a fed state resulted in considerably lower and less variable exposure than found under fasted conditions. Toxicity was less frequent and of lesser severity with lower exposure but limited sample size and large variability prevented reaching that definitive conclusion. Differences in mortality and morbidity between the preliminary terminated chronic and follow-up subchronic studies with the same dose of the same drug lot and similar exposure were not fully resolved as there may be other as yet unclear confounding factors.

 

 

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Author: Chwan-Li Shen and James K. Yeh and Jay J. Cao and Jia-Sheng Wang

Osteoporosis is a major health problem in both elderly women and men. Epidemiological evidence has shown an association between tea consumption and the prevention of age-related bone loss in elderly women and men. Ingestion of green tea and green tea bioactive compounds may be beneficial in mitigating bone loss of this population and decreasing their risk of osteoporotic fractures. This review describes the effect of green tea or its bioactive components on bone health, with an emphasis on (i) the prevalence and etiology of osteoporosis; (ii) the role of oxidative stress and antioxidants in osteoporosis; (iii) green tea composition and bioavailability; (iv) the effects of green tea and its active components on osteogenesis, osteoblastogenesis, and osteoclastogenesis from human epidemiological, animal, as well as cell culture studies; (v) possible mechanisms explaining the osteoprotective effects of green tea bioactive compounds; (vi) other bioactive components in tea that benefit bone health; and (vii) a summary and future direction of green tea and bone health research and the translational aspects. In general, tea and its bioactive components might decrease the risk of fracture by improving bone mineral density and supporting osteoblastic activities while suppressing osteoclastic activities.

 

 

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Author: Q. Li and H.F. Zhao and Z.F. Zhang and Z.G. Liu and X.R. Pei and J.B. Wang and M.Y. Cai and Y. Li

Flavonoid-rich foods have been shown to be effective at reversing age-related deficits in learning and memory in both animals and humans. However, little investigation of the preventative effects of flavonoids on the naturally aged animals was reported. In our study, 14-month-old female C57BL/6 J mice were orally administered 0.025%, 0.05% and 0.1% green tea catechins (GTC, w/v) in drinking water for 6 months; we found that a supplementation with 0.05% or 0.1% GTC prevented age-related spatial learning and memory decline of mice in the Morris water maze. Better performance of GTC-treated mice was associated with increased levels of cAMP-response element binding protein (CREB) phosphorylation in the hippocampus. The expressions of brain-derived neurotrophic factor (BDNF) and Bcl-2, two target genes of CREB which can exhibit long-term regulatory roles in synaptic plasticity and synaptic structure, were also increased. We also found that long-term 0.05% or 0.1% GTC administration prevented age-related reductions of two representative post-synaptic density proteins PSD95 and Ca2+/calmodulin-dependent protein kinase II, suggesting that synaptic structural changes may be involved. These results demonstrated that long-term 0.05% or 0.1% green tea catechin administration may prevent age-related spatial learning and memory decline of female C57BL/6 J mice by regulating hippocampal CREB signaling cascade.

 

 

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Author: Osamu Morita and John F. Knapp and Yasushi Tamaki and Donald G. Stump and John S. Moore and Mark D. Nemec

Evidence suggests that the health benefits associated with green tea consumption are related to tea catechins. The objective of this study was to evaluate potential maternal and fetal effects of standardized heat-sterilized green tea catechins (GTC-H). GTC-H was gavage administered to mated female rats from gestation day 6 through 17, at doses of 0, 200, 600, and 2000 mg/kg/day. There were no GTC-H-related deaths or macroscopic findings. During the entire gestation period in the high-dose (2000 mg/kg/day)-treated group and during days 6–9 and 6–18 in the 600 mg/kg/day group, mean body weight gain was lower. Mean feed consumption was lower during gestation days 6–9 in the 600 mg/kg/day group and during gestation days 6–9 and 9–12 in the 2000 mg/kg/day group. Compared to the control group, mean body weights in the 600 and 2000 mg/kg/day groups were up to 5.1% and 7.7% lower during gestation days 9–20. GTC-H administration did not affect mean gravid uterine weights or intrauterine growth and survival. There were no GTC-H-related fetal malformations or developmental variations. Based on the results of this study, the no-observed-adverse-effect level (NOAEL) for GTC-H was 200 mg/kg/day for maternal toxicity, and 2000 mg/kg/day for embryo/fetal development.

 

 

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Author: Frank Thielecke and Michael Boschmann

The metabolic syndrome (MetS) represents an emerging health burden for governments and health care providers. Particularly relevant for prevention and early management of MetS are lifestyle conditions including physical activity and the diet. It has been shown that green tea, when consumed on a daily basis, supports health. Many of the beneficial effects of green tea are related to its catechin, particularly (−)-epigallocatechin-3-gallate (EGCG), content. There is conclusive evidence from in vitro and animal studies which provide the concepts for underlying functional mechanisms of green tea catechins and their biological actions. An increasing number of human studies have explored the effects of green tea catechins on the major MetS conditions such as obesity, type-2 diabetes and cardiovascular risk factors. This article provides a comprehensive overview of the human studies addressing the potential benefits of green tea catechins on the MetS. The number of human studies in this field is still limited. However, the majority of human epidemiological and intervention studies demonstrate beneficial effects of green tea or green tea extracts, rich in EGCG on weight management, glucose control and cardiovascular risk factors. The optimal dose has not yet been established. The current body of evidence in humans warrants further attention. In particular, well-controlled long-term human studies would help to fully understand the protective effects of green tea catechins on parameters related to the MetS.

 

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Author: Joaudimir Castro and Tara Pregibon and Kristina Chumanov and R. Kenneth Marcus

Presented here is the quantitative analysis of green tea NIST standard reference materials (SRMs) via liquid chromatography-particle beam/electron ionization mass spectrometry (LC-PB/EIMS). Three different NIST green tea standard reference materials (SRM 3254 Camellia sinesis Leaves, SRM 3255 C. sinesisExtract and SRM 3256 Green Tea-containing Oral Dosage Form) are characterized for the content of caffeine and a series of catechin species (gallic acid, catechin, epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin gallate (EGCG)). The absolute limits of detection for caffeine and the catechin species were determined to be on the nanogram level. A reversed-phase chromatographic separation of the green tea reference materials was carried out on a commercial C18 column using a gradient of water (containing 0.1% TFA) and 2:1 methanol:acetonitrile (containing 0.1%TFA) at 0.9 mL min−1 and an analysis time of 50 min. Quantification of caffeine and the catechin species was carried out using the standard addition and internal standard methods, with the latter providing appreciable improvements in precision and recovery.

 

 

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Author: Antonios E. Koutelidakis and Mauro Serafini and Michael Komaitis and Maria Kapsokefalou

We tested in mice the hypothesis that iron fortificants may exert oxidative activity on colon tissue homogenates (CTH), depending on the antioxidant capacity of infusions received with their diet. CTH were obtained from mice receiving daily by gavage 0.1 mL of infusion (8 g/100 mL water) from green tea or white tea or Pelargonium purpureum or catechin (0.01 g/100 mL) or water (control) for five days. All CTH had higher total antioxidant capacity than the control and lower susceptibility to oxidation induced by the retentates of in vitro digests of ferrous lactate, ferrous gluconate, ferrous sulfate and NaFeEDTA. Ferrous sulfate and NaFeEDTA exhibited higher oxidative effect on CTH than ferrous gluconate or ferrous lactate. These results are in support of our hypothesis and suggest that infusions received with diet may protect the colon from a potential oxidative effect of non-absorbed iron.

 

 

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Author: Gang Xu and Guijie Ren and Xia Xu and Huiqing Yuan and Zhenzheng Wang and Ludong Kang and Wenguang Yu and Keli Tian

Author: Keon Wook Kang and Soo Jin Oh and Shi Yong Ryu and Gyu Yong Song and Bong-Hee Kim and Jong Seong Kang and Sang Kyum Kim

The antioxidant activity of catechins isolated from green tea against peroxyl radicals, hydroxyl radicals, and peroxynitrite was determined using the total oxy-radical scavenging capacity (TOSC) assay. (−)-Epicatechin, (−)-epigallocatechin, (−)-epicatechin-3-gallate, and (−)-epigallocatechin-3-gallate were isolated and their structures were characterised based on their physical and spectral properties, and by comparison of these results with similar data in the literature. (−)-Epigallocatechin showed the highest TOSC value, and (−)-epicatechin-3-gallate was the least effective among the catechins tested. These results indicated that the presence of a gallate group at the three position plays a critical role in their antioxidant activity. However, additional insertion of a hydroxyl group at the 5′ position in the B ring attenuates the oxy-radical scavenging capacity of catechins. These results suggest that the antioxidant activity of catechins is dependent on the reactivity of both the original catechins and their products generated during reaction with oxy-radicals.

 

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Author: Norleena P. Gullett and A.R.M. Ruhul Amin and Soley Bayraktar and John M. Pezzuto and Dong M. Shin and Fadlo R. Khuri and Bharat B. Aggarwal and Young-Joon Surh and Omer Kucuk

Botanical and nutritional compounds have been used for the treatment of cancer throughout history. These compounds also may be useful in the prevention of cancer. Population studies suggest that a reduced risk of cancer is associated with high consumption of vegetables and fruits. Thus, the cancer chemopreventive potential of naturally occurring phytochemicals is of great interest. There are numerous reports of cancer chemopreventive activity of dietary botanicals, including cruciferous vegetables such as cabbage and broccoli, Allium vegetables such as garlic and onion, green tea, Citrus fruits, soybeans, tomatoes, berries, and ginger, as well as medicinal plants. Several lead compounds, such as genistein (from soybeans), lycopene (from tomatoes), brassinin (from cruciferous vegetables), sulforaphane (from asparagus), indole-3-carbinol (from broccoli), and resveratrol (from grapes and peanuts) are in preclinical or clinical trials for cancer chemoprevention. Phytochemicals have great potential in cancer prevention because of their safety, low cost, and oral bioavailability. In this review, we discuss potential natural cancer preventive compounds and their mechanisms of action.

 

 

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