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Green Tea Catechins and Their Oxidative Protection in the Rat Eye

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Abstract

Catechins, active constituents of green tea, are well-known antioxidative natural products. It was proposed that green tea extract (GTE) consumption could benefit the eye, and the pharmacokinetics of catechins and oxidation status in rat eye were investigated after oral administration. Sprague-Dawley rats were fed GTE and sacrificed at different time intervals. Their eyes were dissected into cornea, lens, retina, choroid-sclera, vitreous humor, and aqueous humor for analysis of catechins and 8-epi-isoprostane by HPLC-ECD and GC-NCI-MS, respectively. Catechins were differentially distributed in eye tissues. Gallocatechin was present at the highest concentration in the retina, 22729.4 +/- 4229.4 pmol/g, and epigallocatechin in aqueous humor at 602.9 +/- 116.7 nM. The corresponding area-under-curves were 207,000 pmol x h/g and 2035.0 +/- 531.7 nM x h, respectively. The time of maximum concentration of the catechins varied from 0.5 to 12.2 h. Significant reductions in 8-epi-isoprostane levels were found in the compartments except the choroid-sclera or plasma, indicating antioxidative activities of catechins in these tissues.

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... However, whether GTE with high (−)-epigallocatechin gallate (EGCG) content has any potential hazard to the eye is still not known. We have shown that catechins can penetrate into various ocular tissues and exert antioxidative activities after GTE ingestion [33]. In the current study, we use the same dose of GTE but with high level of EGCG to determine the antioxidative, antiinflammatory and antiapoptotic effects. ...
... The unit of normalized AUC was h/L×10 −3 in plasma. The equation for normalized AUC was as follows [33]: ...
... Similar to our previous findings [33] and consistent with other GTE studies in plasma [38,39], exposure levels of EGCG, EGC and EC dominate in the plasma and the main ocular tissues in this study. They were rapidly absorbed and slowly eliminated (Supplementary Table 1) (Fig.1). ...
... Besides the effect of food and drug interaction, we found catechins absorption steric and structural dependent [52]. In one study, we fed 550 mg/kg GTE to SD rats. ...
... After normalization with the input oral doses, the relative AUC 0-20 h of epi-isomers in the plasma was higher than its enantiomers, with the level of EGC > GC, EC > C, and EGCG>GCG. Also, the plasma levels of ungallated catechins (EGC, GC, and EC) were higher than gallated catechins (EGCG, GCG, [52]. ...
... Furthermore, we found that catechins can be distributed into various ocular tissues including aqueous humor, vitreous humor, choroid-sclera, retina, lens, and cornea. After feeding 550 mg/kg GTE to SD rats, the Cmax of GC and ECG can reach to more than 10 and 1 μmol/kg, respectively, in the choroid-sclera and retina and 1 μmol/kg in the lens [52] ( Table 1). Levels of catechins disposed in the ocular tissue could reach the effective dose. ...
... The neuroprotective effects of GTE are partly contributed by the accessibility of various catechin constituents to the ocular tissues. Our recent studies have shown that oral administration of GTE can reach the retinal tissue in sufficient amount to protect it from detrimental insult of oxidative stress 22,23 . In our previous study, when another GTE, Sunphenon DCF-1, is orally administered at the dose of 550 mg/kg to the rats, various catechin constituents are detected in various tissues and compartments of the eye, and the peak concentrations are reached from 0.5 to 12.2 hr 23 . ...
... These catechins are sustained at high levels in the retina. However, penetration level of EGCG is not particularly high 23 . In Theaphenon E, the amount of individual catechin constituents is higher than those in Sunphenon DCF-1, especially EGCG, resulting in increased accumulation of catechins in various ocular tissues. ...
... To determine the most active components of GTE, we studied the neuroprotective effect of GTE and its major constituents. The dosages of catechins tested were in accord to the proportion of each constituent in the GTE Theaphenon E (EGCG: 70.53%, EGC: 4.61%, EC: 3.88%, GC: 0.64%) 23 . The dosages of catechins in the experimental groups are as follows: i) Theaphenon E -550 mg/kg, which has been shown in our earlier study to be the optimal dose that produces potent anti-inflammatory effects against acute uveitis in the rat without causing obvious toxic actions to major organs 22 ...
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Green tea extracts exhibit anti-oxidative and anti-inflammatory actions in different disease conditions. We hypothesized that green tea extract and its catechin constituents ameliorate sodium iodate-induced retinal degeneration in rats by counteracting oxidative stress. In this study, adult Sprague-Dawley rats were intravenously injected with a single dose of sodium iodate. Green tea extract (GTE; Theaphenon-E) or combinations of its catechin constituents, including (-)-epigallocatechin gallate (EGCG), were administered intra-gastrically before injection. Live imaging analysis using confocal scanning laser ophthalmoscopy and spectral-domain optical coherence tomography showed a progressive increase of degenerating profile across the retinal surface and decrease in thickness of outer nuclear layer (ONL) at Day-14 of post-injection. These lesions were significantly ameliorated by Theaphenon-E and catechin combinations with EGCG. Catechins with exclusion of EGCG did not show obvious protective effect. Histological analyses confirmed that Theaphenon-E and catechins containing EGCG protect the retina by reducing ONL disruption. Retinal protective effects were associated with reduced expression of superoxide dismutase, glutathione peroxidase and caspase-3, and suppression of 8-iso-Prostaglandin F2α generation in the retina. In summary, GTE and its catechin constituents are potent anti-oxidants that offer neuroprotection to the outer retinal degeneration after sodium iodate insult, among which EGCG is the most active constituent.
... Green tea extract (Theaphenon E) was generously provided by Dr. Yukihiko Hara (Department of Environmental Physiology, Shimane University Faculty of Medicine, Japan). We have previously characterized the proportion of each catechin constituent in Theaphenon E (EGCG: 70.53%, EGC: 4.61%, EC: 3.88%, and GC: 0.64%) [15]. Green tea extract was suspended in distilled water freshly before application. ...
... In summary, the results from our in vivo investigations revealed that oral intake of GTE is safe and can ameliorate ischemia-induced RGC degeneration and suppress RGC function impairment in rats through the alleviation of cell apoptosis, oxidative stress, and inflammation. Since GTE shows a better protective effect than EGCG in our previous retinal degeneration model [14] and green tea catechins can be found within hours after GTE oral administration [15], this study further supports that GTE can serve as a potent therapeutic agent to RGC degeneration and support the report that tea consumption could possibly be protective against glaucoma development [29]. ...
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Purpose: Oxidative stress induced by reduced blood circulation is a critical pathological damage to retinal ganglion cells (RGCs) in glaucoma. We previously showed that green tea extract (GTE) and its catechin constituents alleviate sodium iodate-induced retinal degeneration in rats. Here, we investigated the therapeutic effect of GTE on ischemia-induced RGC degeneration in rats. Methods: RGC degeneration was induced by ischemic reperfusion in adult Fischer F344 rats. Green tea extract (Theaphenon E) was intragastrically administered 4 times within 48 hours after ischemia. RGC survival, pupillary light reflex, expressions of cell apoptosis, oxidative stress, and inflammation-related proteins were studied. Results: Ischemic reperfusion significantly induced apoptotic RGCs, RGC loss, and larger constricted pupil area compared to the untreated normal rats. Expressions of activated caspase-3 and caspase-8, Sod2, and inflammation-related proteins as well as p38 phosphorylation were significantly upregulated in the ischemia-injured rats. Compared to the saline-fed ischemic rats, significantly higher number of surviving RGCs, less apoptotic RGCs, and smaller constricted pupil area were observed in the GTE-fed ischemic rats. GTE also reduced the increased protein expressions caused by ischemic injury but enhanced the Jak phosphorylation in the retina. Notably, green tea extract did not affect the survival of RGCs in the uninjured normal rats. Conclusions: In summary, GTE offers neuroprotection to RGCs under ischemic challenge, suggesting a potential therapeutic strategy for glaucoma and optic neuropathies.
... Catechins, the major component in green tea extract (GTE), have been shown to exert anti-oxidative, anti-inflammatory, antiangiogenic and anti-carcinogenic effects [28,29]. In a pharmacokinetic study, we have shown that catechins reach peak level in the ocular tissues of normal rats at 1 to 2 hours after ingestion, and produce significant reduction in oxidative stress within these tissues [30]. We have addressed in this study the hypothesis that orally administered GTE could serve as effective anti-inflammatory agents to alleviate inflammatory responses in anterior segments of the eye triggered by a systemic injection of LPS. ...
... No differences were observed among animals treated with one, two or four times of oral administrations of GTE, agreeing with the findings in the histological study. The reason of lack of effect for multiple dosage was unclear, but may be caused by the rapid decline of anti-oxidative property of GTE in the aqueous humor [30]. Treatment with GTE alone without injection of LPS produced neither an accumulation of cells nor an increase in protein exudation in the aqueous humor. ...
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Green tea extract (GTE) ingested by rats exerted anti-oxidative activities in various ocular tissues as shown in our previous studies. The present work investigated anti-inflammatory effects of GTE on endotoxin-induced uveitis (EIU). EIU was generated in adult rats by a footpad injection of 1 mg/kg lipopolysaccharide (LPS). Oral administration of GTE (550 mg/kg) was given one, two or four times after LPS injection. Twenty-four hours later, LPS produced severe hyperemia and edema in the iris. Immunocytochemical examinations showed an accumulation of infiltrating cells in the aqueous humor that were immunopositive for cluster of differentiation 43 (CD43) and CD68, markers for leucocytes and macrophages, respectively. Analyses of the aqueous humor showed an increase in pro-inflammatory mediators including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1). GTE treatments improved the clinical manifestations and reduced infiltrating cells and protein exudation in the aqueous humor, which were not observed under half dose of GTE (275 mg/kg). The number of CD68 positive macrophages residing in the iris and ciliary was also reduced. GTE suppressed production of TNF-α, IL-6 and MCP-1 in the aqueous humor, which was associated with a down-regulation of LPS receptor complex subunits, Toll-like receptor 4 (TLR-4) and CD14, and suppression of nuclear factor-kappa Bp65 (NF-κBp65) in the iris and ciliary body. Our findings show that GTE is a potent anti-inflammatory agent against the inflammation of EIU, and suggest a potential use in treatment of acute uveitis.
... Other Major chemical components of green tea are theanine, caffeine, and vitamin C (Gotoet al., 1996). In vivo and in vitro recent studies have shown that green tea has beneficial ocular effects and that its consumption can protect the eye against oxidative stress (Chu et al., 2010). This may be attributed to the above mentioned free radical scavenging, anti-oxidant, gene modulating activities, and vasodilator effect (Lorenz et al., 2004) together with its ability to cross the blood-brain barrier (Mandel et al., 2006). ...
... These properties are mainly attributed to the green tea constituent, EGCG (Saffari and Sadrzadeh, 2004;Nagle et al., 2006). Chu et al. (2010) found that catechins, particularly EGCG and epigallocatechin, were selectively absorbed into the different eye components. The first documented study of how various eye tissues absorb catechins, raises the possibility that green tea may protect against glaucoma and other common eye diseases. ...
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Ginkgo bilobaand green tea have attracted interest due to their neuroprotective, potent antioxidant, and blood flow regulatory activities. The current study aimed to assess the potential effects of standardized extracts of ginkgo biloba (EGb 761) and green tea on ocular hypertension induced in rabbits by a single subconjunctival administration of betamethasone (3.5 mg). The latter produced a sustainable increase in intraocular pressure (IOP), measured by tonometry, starting from day 7 post administration. Animals were randomly allocated into 10 groups in which group I served as normal. After ocular hypertension has been established namely, day 7, rabbits of group II were left untreated Groups III & IV were topically treated with timolol (0.5 %) &EGb 761 (0.05 %), respectively. Groups V & VI received EGb 761 (20 mg/kg; p.o) & green tea (300 mg/kg; p.o), respectively. Groups VII & VIII received combination of either EGb 761 (20 mg/kg; p.o) or green tea (300 mg/kg; p.o) plus timolol (0.5 %; topically), respectively. All the mentioned treatments were given once daily for 7 days. Two other groups IX & X were also included where EGb 761 (20 mg/kg; p.o) & green tea (300 mg/kg; p.o) were prophylactically given at the same day of betamethasone injection and continued for 2 weeks. IOP was measured and recorded daily. Levels of whole blood reduced glutathione (GSH), plasma malondialdehyde (MDA), and aqueous humor total antioxidant capacity (TAC) were estimated. Corneal histopathological changes were also examined. Levels of IOP and MDA were increased by betamethasone while those of TAC and GSH were decreased, as compared to normal group. Topical timolol and EGb 761 showed similar suppression of the elevated IOP as compared to betamethasone group. Oral EGb 761 and green tea improved the measured biochemical parameters as compared to betamethasone and timolol groups. The treatments improved also the histopathological features of corneal tissue. It merits mention that groups that received combined treatments of either extracts with timolol showed the best results. Prophylactic EGb 761 and green tea prevented the elevation of IOP and improved TAC, MDA, GSH levels as compared to betamethasone group. In conclusion, EGb 761 and green tea might represent a potential avenue for the management of ocular hypertension and adjunctive supplement might be advocated to halt the progress of the disease.
... Recently, an investigation of eye tissues from rats that were fed green tea extract showed that eye structures including choroid-sclera, retina, lens, and cornea absorbed significant amounts of individual flavanols, such as EGC and EGCG. 32 This indicates that green tea consumption may be of benefit to the eyes against oxidative and carbonyl stresses. Human studies in China and the U.S. have found that consuming ∼6 cups a day of green tea for 7 days decreases oxidative DNA damage, lipid peroxidation, and free radical generation in both smokers and nonsmokers. ...
Article
Growing evidence has shown that ascorbic acid (ASA) can contribute to protein glycation and the formation of advanced glycation end products (AGEs), especially in the lens. The mechanism by which ascorbic acid can cause protein glycation probably originates from its oxidized form, dehydroascorbic acid (DASA), which is a reactive dicarbonyl species. In the present study, we demonstrated for the first time that four tea flavanols, (-)-epigallocatechin 3-O-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin 3-O-gallate (ECG), and (-)-epicatechin (EC), could significantly trap DASA and consequently form 6C- or 8C-ascorbyl conjugates. Among these four flavanols, EGCG exerted the strongest trapping efficacy by capturing approximate 80% of DASA within 60 min. We successfully purified and identified seven 6C- or 8C-ascorbyl conjugates of flavanols from the chemical reaction between tea flavanols and DASA under slightly basic conditions. Of which, five ascorbyl conjugates, EGCGDASA-2, EGCDASA-2, ECGDASA-1, ECGDASA-2 and ECDASA-1, were recognized as novel compounds. The NMR data showed that positions 6 and 8 of the ring A of flavanols were the major active sites for trapping DASA. We further demonstrated that tea flavanols could effectively inhibit the formation of DASA-induced AGEs via trapping DASA in the bovine lens crystallines-DASA assay. In this assay, 8C-ascorbyl conjugates of flavanols were detected as the major adducts using LC-MS. This study suggests that daily consumption of tea flavanols beverage may prevent protein glycation in lens induced by ascorbic acid and its oxidized products.
... It acts as a free radical scavenger and is widely recognised as a protectant against oxidative stress in a number of systems. Green tea extract contains epigallocatechin gallate (EGCG) a catechin with acts as a powerful antioxidant and has been shown in a mouse model to modify progression to the diabetic state [22,23] as well as to alleviate oxidative damage in the rat eye [24] and inhibit cataract formation in the rat streptozotocin-induced diabetes model [25,26]. ...
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The majority of dogs with diabetes mellitus develop blinding mature cataracts through the action of the enzyme aldose reductase producing sorbitol with osmotic action drawing water into the lens thus causing opacification. Here we evaluate the use of OcuGLO™ a formulation including the aldose reductase inhibitor alpha lipoic acid, grapeseed extract, carotenoids, omega-3-fatty acids, and coenzyme Q10 in the prevention of canine diabetic cataract in a prospective placebo-controlled double-masked study. Materials and methods: Dogs with diabetes mellitus but as yet without the development of blinding diabetic cataracts were given either OcuGLO™ or a placebo containing antioxidant vitamins. Dogs were examined monthly and their degree of lens opacification documented photographically using a Genesis D fundus camera at +10D. Time to progression of lens opacification was documented and compared between the OcuGLO™ group and the placebo group, using Kaplan Meier survival curve statistics Results: Mean time without change in lens opacification was 278 ± 184 days with OcuGLO Rx™ and 77 ± 40 days in the placebo group this difference being statistically significant at p=0.0005. Twelve of 15 dogs taking the placebo developed significantly increased lens opacification while 5 of 15 dogs taking OcuGLO Rx™ developed significant cataract. of these five dogs four animals did not receive daily OcuGLO Rx™ as directed due to unrelated concurrent illness or owner non-compliance. The remaining dog progressed despite Ocu-GLO Rx™ administration. In two dogs, diabetic cataract was reversed with regained vision on Ocu-GLO Rx™. Discussion: This small preliminary study demonstrates that oral Ocu-GLO Rx™ has beneficial effects in delaying cataract formation in dogs with diabetes mellitus. We look forward to further studies with larger case populations but note that the statistical significance reached between placebo and supplement-treated group, even with a small study population, demonstrates the efficacy of this commercially available dietary supplement.
... Kolejna rola wynika z obecności w żywności substancji bioaktywnych, które wpływają na obniżenie ryzyka zachorowania na wiele przewlekłych chorób niezakaźnych, m.in. nowotworów, arteriosklerozy i cukrzycy typu 2. Związki te mogą przyczyniać się do poprawy zdrowia człowieka bądź też odgrywać istotną rolę w profilaktyce chorób [20,26]. Wyniki badań epide- ...
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Cereals grains are a rich source of biologically active compounds. They have antioxidant properties that depend on their chemical structure. This review paper depicted the physical and chemical composition of antioxidants, their chemical forms, and their contents in the grains of wheat, rye, oats, barley, and buckwheat. A general characteristic of the following groups of the antioxidants was represented: vitamins, carotenoids, phenolic compounds including phenolic acids and flavonoids, phytoestrogens, phytosterols, inositol phosphates, glutathione and melatonin, as was their role as antioxidants in preserving the homeostasis in human body. Discussed was the effect of milling grains and hydro-thermally processing them on the antioxidant potential of cereal-based products. The essential facts were provided on how new antioxidants were formed during the Maillard reaction after the hydrothermal treatment of cereal grains. Based on the constructive correlation as confirmed to exist between the consumption of whole grain products and the decreased occurrence level of non-communicable chronic diseases, as well as on the current dietary recommendations to increase the consumption of whole grain cereal products, the authors emphasis the necessity to pursue extended research into antioxidants in cereal grains and the health-promoting value of whole grain cereal products pursue.
... Green tea consumption led to maximum concentration of gallocatechin in retina and epigallocatechin in aqueous humor within 0.5 to 12.2 h exerting their antioxidant power and reducing the formed toxic metabolite 8-epi-isoprostane levels [157]. After observing the effects of carotenoids, polyphenols and vitamins C and E on lutein absorption, Reboul et al. [158] mentioned that a mixture of polyphenols (gallic acid, caffeic acid, (+)-catechin and naringenin) and carotenoids (lycopene plus beta-carotene) showed higher impairing affinity, while vitamins C and E had no significant effect. ...
Article
Ocular region is a complex structure, which allows conscious light perception, and vision, it is of ecto-mesodermal origin. Cholesterol and polyunsaturated fatty acids are involved in retinal cell function; however, hypercholesterolemia and diabetes impaired its function. Retinal damage, neovascularization and cataracts are the main complications of cholesterol overload. Dietary supplementation of the selected plant products led to the scavenging of free reactive oxygen species thereby protecting the ocular regions from the damage of hypercholesterolemia. The present review illustrates the dramatic effects of increased cholesterol level on the ocular regions. The impact of phytotherapy is discussed in relation with the different regions of the eye including retina, cornea and lens.
... It acts as a free radical scavenger and is widely recognised as a protectant against oxidative stress in a number of systems. Green tea extract contains epigallocatechin gallate (EGCG) a catechin with acts as a powerful antioxidant and has been shown in a mouse model to modify progression to the diabetic state [22,23] as well as to alleviate oxidative damage in the rat eye [24] and inhibit cataract formation in the rat streptozotocin-induced diabetes model [25,26]. ...
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This is the final published version. It first appeared at http://clinmedlibrary.com/articles/ijdcr/ijdcr-2-023.php?jid=ijdcr.
... Antioxidants are substances which significantly delay or inhibit the oxidation reaction, being at many times lower concentration than oxidizing agents. Providing proper supply of these compounds in the diet reduced the risk of diabetes, obesity, coronary heart disease, and even tumors [4]. Polyphenols content in materials as well as their activity depends on the plant species, cultivars, as well as the state of maturity and changes during the technological processing. ...
Article
Background: Buckwheat, despite its broad nutritional benefits, is still not widely appreciated grain. It contains a protein with preferred amino acid composition and it is a valuable source of micronutrients and vitamins of the B group and vitamin E. Moreover, buckwheat groats have a high amount of polyphenols, including flavonoids and flavones. Eating rye bread is beneficial due to its high content of dietary fiber, phenolic acids and characteristic taste and aroma. Therefore, the use of rye flour and buckwheat mill products for bread may allow obtaining a product of high nutritional value and flavor. Objective: The aim of the study was to evaluate the influence of buckwheat products addition and baking process on the antioxidant properties of rye-buckwheat blends and breads. Material and methods: Experimental material was rye flour type 580 and buckwheat flour, wholegrain flour and bran obtained by grinding buckwheat groats. Buckwheat products share was 20 and 35%. The control was the rye flour. In the rye-buckwheat blends and bread loaves, the contents of selected flavonoids by HPLC method, total polyphenols content by Folin-Ciocalteu method and the antioxidant activity by the DPPH˙ radical scavenging method were determined. Results: Buckwheat bran was significantly richer in total polyphenols, rutin, quercetin, orientin and isoorientin than other buckwheat products and rye flour. Bread after baking contained similar amount of total polyphenols and quercetin and have a comparable ability to scavenge 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH˙) than the corresponding blends. Baking process negatively affected the amount of rutin, orientin and isoorientin. Conclusions: The use of buckwheat bran as a replacement for wheat flour in bread significantly increases its nutritional value. The process of baking unequally affects the content of particular groups of antioxidant compounds. Key words: antioxidants, buckwheat, flavonoids, rutin, quercetin, polyphenols.
... Green tea "catechins" are among a number of antioxidants such as vitamin C, vitamin E, lutein, and zeaxanthin thought capable of protecting the eye 56 . A study conducted at Chosun University College of Medicine in Korea discovered that the green tea antioxidant EGCG can protect human retina against UV damage. ...
... Wolfram et al. (2006) report evidence that catechins and epigallocatechin gallate (EGCG) in green tea reduce adipocytes differentiation and proliferation, lipogensis i.e., birth of new fat cells; fat mass, body weight, fat oxidation, plasma levels of triglyceride, free fatty acids, cholesterol, glucose, insulin and leptin and increased beta-oxidation and thermogenesis. Chu et al. (2010) reported that green tea "catechins" are among a number of antioxidants such as vitamin C, vitamin E, lutein, and zeaxanthin thought capable of protecting the eye. Combination of these two products, fermented glutinous rice and green tea, as enricher of the es puter is expected to increase popularity and health benefits of es puter. ...
Article
Fermented black glutinous rice (Oryza sativa glutinosa L.) and green tea (Camellia sinensis L.) contain bioactive compounds including anthocyanins and flavonoids which have potential to enrich es puter, one of the favorite traditional frozen desserts in Indonesia, as a functional food. This study aimed to get the best formula of es puter enriched by fermented black glutinous rice and green tea. The local variety of fermented black glutinous rice (FBGR) was prepared by steaming until cooked then fermented by using ragi tape (traditional yeast cake) at 27°C for 3 days. A factorial design experiment was used to study the effects of proportion of FBGR (25, 30, and 35%) and green tea powder (2, 3, and 4%) on the physical and chemical properties of es puter. The results showed that the FBGR had higher total phenolic content, antioxidant activity, and anthocyanin content than the unfermented black glutinous rice (p<0.05). The best es puter formula consisted of 30% FBGR, 4% green tea powder, 51.2% coconut milk, 14% sugar, 0.4% salt, 0.2% sodium carboxymethyl cellulose and 0.2% glycerol monostearate. The physical characteristics of this formula were accepted with 33.46±0.26% total solid, 7.31±0.10% overrun, 2,794.33±0.58 cP viscosity, and 9.57±0.87 min melting time. The antioxidant activity (DPPH), phenolic content and anthocyanin content were 1,865.81±161.63 μmol TE/100g dry basis, 0.09±0.01 GAE in g/100g sample and 0.30±0.11 mg/100g sample dry basis, respectively. This formula had overall liking score 6.5 which indicated that the modified es puter was liked moderately. In addition, consumer acceptance was conducted using 100 consumers and sixty-five percent of consumers accepted this product.
... Osborne et al., [128] in rat studies with oral administration of epigallocatechin dem-onstrated a reduced light-induced retinal neuronal death, suggesting that this substance can be useful for preventing retinal neurons damage and death. In fact, Chu et al., [129] in experiments with rats that drank green tea, reported that the retina absorbed the highest levels of gallocatechin, and the aqueous humor better absorbed epigallocatechin. These data confirmed that green tea consumption could protect our eyes against oxidative attack. ...
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Background: Primary open-angle glaucoma (POAG) is a multifactorial pathology involving a variety of pathogenic mechanisms, including oxidative/nitrosative stress. This latter is the consequence of the imbalance between excessive formation and insufficient protection against reactive oxygen/nitrogen species. Objective: Our main goal is to gather molecular information to better managing pathologic variants that may determine the individual susceptibility to oxidative/nitrosative stress (OS/NS) and POAG. Method: An extensive search of the scientific literature was conducted using PUBMED, the Web of Science, the Cochrane Library, and other references on the topic of POAG and OS/NS from human and animal model studies published between 2010 and 2017. Finally, 152 works containing relevant information that may help understanding the role of antioxidants, essential fatty acids, natural compounds and other similar strategies for counteracting OS/NS in POAG were considered. Results: A wide variety of studies have proven that antioxidants, among them vitamins B3, C and E, Coenzyme Q10 or melatonin, -3/-6 fatty acids and other natural compounds (such as coffee, green tea, bear bile, gingko biloba, coleus, tropical fruits, etc.,) may help regulating the intraocular pressure as well as protecting the retinal neurons against OS/NS in POAG. Conclusion: Based on the impact of antioxidants and -3/-6 fatty acids at the molecular level in the glaucomatous anterior and posterior eye segments, further studies are needed by integrating all issues involved in glaucoma pathogenesis, endogenous and exogenous risk factors and their interactions that will allow us to reach newer effective biotherapies for preventing glaucomatous irreversible blindness.
... Green tea extract (GTE), Theaphenon E ® , kindly provided by Dr. Yukihiko Hara, contained 70% epigallocatechin gallate (EGCG), 5% epigallate catechins (EGC), 4% epicatechin (EC), 0.6% gallocatechin (GC) and had been assessed in our laboratory (20). The optimal dose, 550 mg/kg, for anti-inflammatory effects against the EIU has been verified (21). ...
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Introduction Green tea extract (GTE) alleviated ocular inflammations in endotoxin-induced uveitis (EIU) rat model induced by lipopolysaccharide (LPS) but the underlying mechanism is unclear. Objectives To investigate the systematic and local mechanisms of the alleviation by untargeted metabolomics using liquid chromatography-tandem mass spectrometry Methods Sprague-Dawley rats were divided into control group, LPS treatment group, and LPS treatment group treated with GTE two hours after LPS injection. The eyes were monitored by slip lamp and electroretinography examination after 24 hours. The plasma and retina were collected for metabolomics analysis Results In LPS treated rats, the iris showed hyperemia. Plasma prostaglandins, arachidonic acids, corticosteroid metabolites, and bile acid metabolites increased. In the retina, histamine antagonists, corticosteroids, membrane phospholipids, free antioxidants, and sugars also increased but fatty acid metabolites, N-acetylglucosamine-6-sulphate, pyrocatechol, and adipic acid decreased. After GTE treatment, the a- and b- waves of electroretinography increased by 13%. Plasma phosphorylcholine lipids increased but plasma prostaglandin E1, cholanic metabolites, and glutarylglycine decreased. In the retina, tetranor-PGAM, pantothenic derivatives, 2-ethylacylcarinitine, and kynuramine levels decreased but anti-oxidative seleno-peptide level increased. Only phospholipids, fatty acids, and arachidonic acid metabolites in plasma and in the retina had significant correlation (p < 0.05, r > 0.4 or r < -0.4). Conclusions The results showed GTE indirectly induced systemic phosphorylcholine lipids to suppress inflammatory responses, hepatic damage, and respiratory mitochondrial stress in EIU rats induced by LPS. Phospholipids may be a therapeutic target of GTE for anterior chamber inflammation
... The green tea extract Theaphenon E was kindly provided by Dr. Y. Hara. It contains a mixture of EGCG (epigallocatechin gallate, 70.53%), EGC (epigallate catechins, 4.61%), EC (epicatechin, 3.88%) and GC (gallocatechin, 0.64%), and other trace catechin derivatives 40 . It was prepared as a 550 mg/kg or 275 mg/ kg suspension in 0.5 ml distilled water and was immediately fed intragastrically into the rat. ...
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Inflammation is in a wide spectrum of retinal diseases, causing irreversible blindness and visual impairment. We have previously demonstrated that Green Tea Extract (GTE) is a potent anti-inflammatory agent for anterior uveitis. Here we investigated the anti-inflammatory effect of GTE on lipopolysaccharides (LPS)-induced retinal inflammation in rats and explored the underlying mechanism. Adult rats were injected with LPS and GTE was administered intra-gastrically at 2, 8, 26 and 32 hours post-injection. Staining of whole-mount retina showed that the number of activated microglia cells was significantly increased at 48 hours post-injection, which was suppressed after GTE treatment in a dose-dependent manner. Activation of astrocytes and Müller glia in the retina was also suppressed after GTE treatment. Meanwhile, GTE reduced the expression of pro-inflammatory cytokines including IL-1β, TNF-α and IL-6 in retina and vitreous humor. These anti-inflammatory effects were associated with a reduced phosphorylation of STAT3 and NF-κB in the retina. Furthermore, the surface receptor of EGCG, 67LR, was localized on the neurons and glia in the retina. These findings demonstrate that GTE is an effective agent in suppressing LPS-induced retinal inflammation, probably through its potent anti-oxidative property and a receptor-mediated action on transcription factors that regulate production of pro-inflammatory cytokines.
... EGCG potently and specifically inhibits a small number of important molecular targets at concentrations that may be achieved by consuming green tea or EGCG-rich dietary supplements (Carlson et al. 2007). EGCG possesses many potential anti-carcinogenic functions and as an antioxidant serving to neutralize free radicals in the body before they damage cells and was confirmed by the influence of catechins on rat eye (Zhen 2002; Kai et al. 2010). Catechins are usually isolated by extraction with organic solvents, supercritical fluids and solid phase extraction. ...
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Fresh frozen tea leaves (Camellia assamica L.) were extracted with SC-CO2 to obtain polyphenols rich in EGCG and compared with conventional solvent extraction. Extraction parameters such as temperature, pressure and solvent to material ratio were critical factors in extraction and optimized by response surface methodology (RSM). The maximum yield of extractable solids using SC-CO2 with ethanol entrainer was carried out at pressures 150 to 350 bar, temperatures from 40 °C to 60 °C and solvent to material ratio 100 to 200. The theoretical yield was 3.91 % (w/w), while experimental yield was 4.20 ± 0.27 % (w/w) at temperature of 50 °C, pressure 250 bar and solvent to material ratio of 200. The chemical compositions of extracted solids were investigated by HPLC which showed 722.68–848.09 ± 1.12 mg of EGCG/g of extractable solids were separated in SC-CO2. Also, 54.62 ± 1.19 mg of EGCG/g of extractable solids was separated using conventional extraction which is quantitatively lesser than SC-CO2 extraction yield. Thus, SC-CO2 extraction was proved to be effective technique in obtaining extracts rich in EGCG (>95 %).
... The consumption of Camellia sinensis green tea is especially popular in Asian countries, and its association with antioxidant and hepatoprotective effects has brought about the inclusion of green tea extracts as common botanical ingredients in dietary supplements, nutraceuticals, and functional foods (Chu et al., 2010). Generally speaking, the tea polyphenols (catechins) are regarded as the major bioactive compounds (Yang et al., 2006). ...
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This study was designed to investigate the hepatoprotective effects of the tea polysaccharides (ZTPs) extracted from a selenium-enriched Ziyang green tea (Camellia sinensis). ZTPs were identified as the heteropolysaccharides with glucose (31.4%), arabinose (23.5%) and galactose (21.8%) being the main constitutive monosaccharides. ZTPs displayed noteworthy scavenging effects against DPPH, OH and O2(-), and high antioxidant effects in vitro, and the effects were further verified by suppressing CCl4-induced oxidative liver damage in mice at 100, 200 and 400mg/kg BW. Administration of ZTPs in mice prior to CCl4 significantly prevented the CCl4-induced increases in serum alanine aminotransferase, aspartate aminotransferase and lactic dehydrogenase, as well as hepatic malondialdehyde level. Mice treated with ZTPs showed normal glutathione peroxidase and superoxide dismutase activities, relative to CCl4-treated group. ZTPs also prevented the CCl4-caused liver histological alteration, as indicated by histopathological evaluation. These findings demonstrate that ZTPs have protective effects against acute CCl4-induced oxidative liver damage.
... There are few animal studies investigating the uptake and distribution of green tea catechins in ocular tissues and fluids in rats through oral administration. By sacrificing GTE-fed rats at different time intervals to analyze cornea, lens, retina, choroid/sclera, aqueous humor and vitreous humor separately, Chu et al. documented the differential distribution of catechins in various eye tissues (48). GTE was highly concentrated in retina and aqueous humor. ...
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Ocular inflammation is a common complication of various eye diseases with wide consequences from irritations to potentially sight-threatening complications. Green tea is a popular beverage throughout the world. One of the proven health benefits of consuming green tea extract (GTE) is anti-inflammation. Catechins are the biologically active constituents of GTE. In in vitro and in vivo studies, GTE and catechins present inhibition of inflammatory responses in the development of ocular inflammation including infectious, non-infectious or autoimmune, and oxidative-induced complications. Research on the ocular inflammation in animal models has made significant progress in the past decades and several key disease mechanisms have been identified. Here we review the experimental investigations on the effects of GTE and catechins on various ocular inflammation related diseases including glaucoma, age-related macular degeneration, uveitis and ocular surface inflammation. We also review the pharmacokinetics of GTE constituents and safety of green tea consumption. We discuss the insights and perspectives of these experimental results, which would be useful for future development of novel therapeutics in human.
... Interleukin-β1 induces secretion of interleukin-6 and interleukin-8 which also play a role as pro-inflammatory cytokines and are important for the initiation and increase of the inflammatory response to microbial infection [42]. In addition, GTE anti-inflammatory effect was confirmed in animal studies on LPS-induced retinal inflammation [43,44]. ...
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Objectives This in vitro study aimed to analyze the anti-inflammatory and wound healing potential of green tea extract (GTE) in human gingival epithelial keratinocytes (HGEK) treated with lipopolysaccharides (LPS). Materials and methods A cell viability assay was conducted using MTT to determine nontoxic levels of GTE on immortalized HGEK. Cells were concomitantly treated with LPS (1 μg/ml) and GTE (1 mg/ml, 2.5 mg/ml, 5 mg/ml, and 10 mg/ml) to assess inflammation. Gene expression levels of inflammatory markers IL-β1, IL-6, and TNFα were measured by RT-PCR and their protein production was assessed by ELISA. The scratch wound healing assay was used to investigate the effects of different concentrations of GTE on cell migration. We also explored the effect of GTE on the induction of the Nrf2/HO-1 pathway in the cells with or without LPS. Results GTE at concentrations of 2.5 mg/ml, 5 mg/ml, and 10 mg/ml significantly enhanced cell viability (p < 0.05). And IL-β1, IL-6, and TNFα gene expression presented up to 10-fold decrease compared with LPS-treated cells, which was also similarly found on the protein levels. At the same concentrations, cell migration increased. Conclusions The mechanism results showed that GTE produced the anti-inflammatory response by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and increasing the level of anti-oxidant protein heme oxygenase-1 (HO-1). Clinical relevance GTE may be potentially used as oral rinse anti-inflammatory drug for treatment and prevention of oral inflammatory diseases, which is shown here by the ability to reduce the inflammation and increase in cell migration in a dose-dependent manner.
... Multiple studies have demonstrated that catechin had various protective effects on neurons both in vitro and in vivo, potentially lowering the risk of alzheimer's disease and Parkinson's disease [9][10][11][12][13] . it can also attenuate the ethanol-induced oxidative stress in aged mice and significantly against the beta-amyloid induced neurotoxicity in cultured hippocampal neurons [14][15][16] . in addition, studies had also showed that oral administration of green tea extract can reach the retinal tissue in sufficient amount and perform anti-oxidative effect 17,18 . ...
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Backgrounds Previous studies were mainly focused on the effect of catechins and caffeine, the main pharmacological ingredients of green tea. However, the ordinary way of taking green tea is by drinking the tea water. Hence the benefits of water extractives of green tea were investigated in the current study. Methods H2O2 was applied to induce the oxidative stress on PC12 cells. The neuroprotective effects of green tea against oxidative stress were determined by observing the biological behaviors of PC12 cells. Results With the pre-treatment of light green tea, the survival and proliferation of oxidative stressed PC12 cells were significantly enhanced. H2O2 induced PC12 cell apoptosis was completely reversed. Consistently, the expression of JNK was up-regulated while the caspase-3 was down-regulated. Conclusion These results suggested that drinking green tea, particularly the light green tea, performed neuroprotective effects against oxidative stress.
... Flavonoids possess several bioactive properties including anti-oxidant, anti-inflammatory, and neuroprotective effects [28]. Studies have reported that flavonoids can reduce oxidative stress [28,29] and improve ocular blood flow in POAG [30]. Myricetin, (3,5,7,3' ,4' ,5'-hexahydroxyflavone) is present in apples, oranges, berries, and vegetables. ...
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We investigated the effects of an ethanol extract of C. denticulatum (EECD) in a mouse model of glaucoma established by optic nerve crush (ONC), and found that EECD significantly protected against retinal ganglion cell (RGC) death caused by ONC. Furthermore, EECD effectively protected against N-methyl-D-aspartate-induced damage to the rat retinas. In vitro, EECD attenuated RGC-5 death and significantly blunted the up-regulation of apoptotic proteins induced by 1-buthionine-(S,R)-sulfoximine combined with glutamate, reduced reactive oxygen species production by radical species, and inhibited lipid peroxidation. The major EECD components were found to be chicoric acid and 3,5-dicaffeoylquinic acid (3,5-DCQA) that have shown beneficial effects on retinal degeneration both in vitro and in vivo studies. Thus, EECD could be used as a natural neuroprotective component for glaucoma, and chicoric acid and 3,5-DCQA as mark compounds for the development of functional food.
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Background Retinitis pigmentosa (RP) is a group of inherited neurodegenerative human diseases characterized by the loss of photoreceptor cells by apoptosis and eventual blindness. A single intraperitoneal (ip) injection of N-methyl-N-nitrosourea (MNU) causes photoreceptor cell apoptosis within 7 days in rats. Green tea extract (THEA-FLAN 90S; GTE) is a common herbal supplement with pluripotent properties including antioxidant activity. The purpose of the present study was to evaluate the efficacy of GTE against photoreceptor apoptosis in 7-week-old female Sprague-Dawley rats that received a single ip injection of 40 mg/kg MNU. Methods The oral administration of 250 mg/kg/day GTE was initiated 3 days prior to MNU injection and continued once daily throughout the experiment. Rats were sacrificed at 12, 24, and 72 h and 7 days after MNU injection, and the eyes were examined morphologically and morphometrically. The photoreceptor cell ratio, retinal damage ratio, and retinal preservation ratio were used to determine the structural and functional alterations. The number of apoptotic photoreceptor cells per mm2 was determined in situ by TdT-mediated dUTP-digoxigenin nick end labeling (TUNEL). Our results indicated that oral administration of GTE significantly suppressed the loss of photoreceptor cells morphometrically 7 days after MNU injection. The number of TUNEL-positive cells per mm2 in MNU-exposed rat central retina with or without GTE administration was 981 vs. 2056 at 24 h after MNU injection. Conclusions GTE structurally and functionally suppressed MNU-induced photoreceptor cell apoptosis. These findings indicate that GTE may help to ameliorate the onset and progression of human RP.
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Green tea in its purest and most unadulterated form has always influenced human health from generations and day by day scientific evidences throughout the world are making people aware of health benefits associated with this herbal drink. Though Green Tea is not officially recognized as a medical agent, it is one of the most researched plant-based remedies whose possible benefits include promotion of cardio-vascular health, cancer prevention, skin protection, and antioxidant activity, to fight high cholesterol levels, infection, impaired immune function, diarrhoea, fatigue and many more. Laboratory findings have revealed that notable health benefit of green tea is its powerful antioxidants potential which at the molecular level, helps prevent cellular damage from certain oxidation reactions in the body. The credit for their useful antioxidant property lies with their huge collection of chemical substances called polyphenols and catechins make the major contribution of them. Though catechins have been found in other plants derivatives such as grapes, pomegranates, those found in tea have proven to be the most effective antioxidants known. The catechins epigallocatechin gallate (EGCG) is found in the greatest concentration and most studied for its health benefits. There is an urgent need to check the efficacy, safety and translational guidelines for a green tea to be used as safe, effective drug. The main objective of this review is to enlighten some recent facts with relevance to the current status and advance in green tea benefits.
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The catechins composition of tea polyphenols with different extracted methods was analysed by HPLC. The aim is to compare the extraction effect of water-extracting and alcohol-extracting method, the purification effect of solvent extraction and ionic precipitation method. The results indicated that organic solvent extraction method can improve the extraction rate of catechins, especially can increase the content of estered catechins. In the technic of organic solvent extraction, the total content of catechins can effectively be increased by using alcohol extraction. Ion precipitation can enhance the content of gallocatechins,while organic solvent extraction can raise the contents of catechins,EC and estered catechins.
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Chapter
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Green tea (Camellia sinensis) always influenced human health benefits associated with this herbal drink. Green tea has possible benefits include promotion of cardio-vascular health, cancer prevention, skin protection, and antioxidant activity, to fight high cholesterol levels, infection, impaired immune system, diarrhoea, fatigue and much more. The credit for their useful antioxidant property exists with their huge collection of chemical substances called polyphenols and catechins make the major contribution to them. In addition, its content of certain minerals and vitamins increases the antioxidant potential of this type of tea The present paper reviews the geographical distribution, history, cultivation, uses, side effects, synonyms, botanical description, taxonomical classification, phytochemical constituents and pharmacological activities.
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Carotenoids are present in many biological systems, often decreasing the formation of products of oxidative damage to biological molecules. In the macula their concentration is so high that it has been believed that the yellow color filters out damaging blue light. Recent reports that dietary lutein reduces the risk of cataract in the eye lens suggested that the antioxidant action of carotenoids, which has been inferred from decreased oxidative damage, warranted further direct investigation. Superoxide and hydroxyl radical scavenging by lutein and zeaxanthin (retinal carotenoids), beta-carotene, lycopene, lutein esters (from marigolds), and a commercial mixture of soy carotenoids were compared to scavenging by ascorbate and ascorbyl palmitate. Radical scavenging was measured with a chemiluminescent assay (luminol) and by electron spin resonance, ESR. Inhibitory concentrations, IC(50), were determined with the luminescent assay. All of the carotenoids scavenged both superoxide (in ESR 30-50% at 16.7 microM) and hydroxyl radicals (in ESR 50-70% at 16.7 microM, in a luminescent assay 90-99%). While crocin may be unable to scavenge superoxide, some of the other carotenoids do so quite effectively. The mixtures of 15,15'-cis and all-trans-carotenoids studied by ESR and luminescent assay scavenge both superoxide and hydroxyl radicals. Lycopene and beta-carotene both scavenge superoxide more effectively than the xanthophylls of the retina, zeaxanthin and lutein. All of the carotenoids examined scavenged the hydroxyl radicals more effectively than superoxide radicals. The predominant carotenoid in the fovea of the retina, zeaxanthin, scavenged hydroxyl radicals more effectively than the other retinal carotenoid, lutein. Possible mechanisms of radical scavenging by the carotenoids are discussed.
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Canned and bottled tea drinks contain not only green tea epicatechins (GTE), namely (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC), but also four GTE epimers, namely (-)-gallocatechin gallate (GCG), (-)-catechin gallate (CG), (-)-gallocatechin (GC) and (-)-catechin (C). In the present study we examined the antioxidant activity and bioavailability of these epimers compared with their corresponding precursors. The epimerisation reaction was induced by autoclaving GTE extract derived from longjing green tea at 120degreesC for 20 min. Isolation and purification of each GTE and epimer were accomplished by various column chromatographic and semi-preparative HPLC techniques. The antioxidant activity of each epimer with its corresponding GTE precursor was conducted in the three in vitro systems, namely human LDL oxidation, ferric reducing-antioxidant power (FRAP), and anti-2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assays. The results of all three assays demonstrated that CG had similar antioxidant activity with its precursor ECG, while GC was less potent as an antioxidant than its precursor EGC. Regarding EGCG and GCG, the antioxidant potency was similar for both LDL oxidation and DPPH free radical assays, but GCG was statistically less effective than EGCG in the FRAP assay. For EC and C, the latter had less anti-free radical activity in the DPPH assay, but in LDL oxidation and FRAP assays the antioxidant activity was similar. Oral and intravenous dosing of GTE-epimer mixture led to increase in total plasma antioxidant capacity in rats. In general, both epicatechins and epimers had low bioavailability (00.8-0.31) and most of the observed differences between epicatechins and their corresponding epimers were small, even if they were statistically significant in some cases. It was concluded that the epimerisation reaction occurring in manufacturing canned and bottled tea drinks would not significantly affect antioxidant activity and bioavailability of total tea polyphenols.
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Epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea (Camellia sinensis), has shown cancer preventive activity in animal models. The bioavailability of EGCG in the most commonly used animal species, mice, is poorly understood. Moreover, the pharmacokinetic parameters of EGCG have not been reported previously in mice. Here we report that after administration of EGCG intravenously at 21.8 mumol/kg or intragastrically at 163.8 mumol/kg, the peak plasma levels of EGCG in male CF-1 mice were 2.7 +/- 0.7 and 0.28 +/- 0.08 mumol/L, respectively. EGCG was present mainly (50-90%) as the glucuronide. The plasma bioavailability of EGCG after intragastric administration was higher than previously reported in rats (26.5 +/- 7.5% vs. 1.6 +/- 0.6%). The conjugated EGCG displayed a shorter t(1/2) (82.8-211.5 vs 804.9-1102.3 min) than unconjugated EGCG (P < 0.01, Student's t test). EGCG was present in the unconjugated form in the lung, prostate and other tissues at levels of 0.31-3.56 nmol/g after intravenous administration. Although intragastric administration resulted in lower levels in most tissues compared with intravenous administration (e.g., 0.006 +/- 0.004 vs. 2.66 +/- 1.0 nmol/g in the lung), the levels in the small intestine and colon were high at 45.2 +/- 13.5 and 7.86 +/- 2.4 nmol/g, respectively. This is the first report of the pharmacokinetic parameters of EGCG in mice. Such information provides a basis for understanding the bioavailability of EGCG in mice and should aid in understanding the cancer preventive activity of EGCG. J. Nutr. 133: 4172-4177, 2003.
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Isoprostanes (IsoP's) are a series of prostaglandin(PG)-like compounds that are formed independent of the cyclooxygenase by free radical catalyzed peroxidation of arachidonic acid esterified to phosophlipids. New insights regarding the enzymatic hydrolysis of preformed esterified Isop's will be presented. The initial series of Isop's identified had a prostanoid F-type ring structure (F2-Isop's). Subsequently, Isop's with prostanoid E-type and D-type ring structures were identified (E2D2-Isop's). Additional unique products of this pathway (isothromboxanes and isolevuglandins) have been recently identified and will be discussed. Two Isop's that have been tested for bioactivity (8-iso-PGF2α and 8-iso-PGE2) have been found to be potent vasoconstrictors via interaction with a receptor(s). Isolevuglandins, on the other hand, exert unique biological properties owing to their remarkable proclivity to form covalent adducts with proteins and DNA. A valuable aspect of the discovery of Isop's is that measurements of Isop's in biological fluids and tissues offers a reliable means to assess oxidative stress status in vivo. Examples of how measurement of Isop's has proven useful to assess the role of free radicals in human disease, with an emphasis on atherosclerosis/cardiovascular disease, will be discussed.
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A number of in vitro studies have shown that polyphenols and flavonoids in tea exert significant antioxidant activity. However, epidemiologic and experimental studies have produced conflicting results. The purpose of the present study was to compare the antioxidant activity of black tea in vitro with that ex vivo. Black tea polyphenols (BTP), black tea extract (BTE), or their major polyphenolic antioxidant constituent, epigallocatechin gallate (EGCG), were added to human plasma and lipid peroxidation was induced by the water-soluble radical generator 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH). Following a lag phase, lipid peroxidation was initiated and occurred at a rate that was lowered in a dose-dependent manner by BTP. Similarly, EGCG and BTE added to plasma in vitro strongly inhibited AAPH-induced lipid peroxidation. The lag phase preceding detectable lipid peroxidation was due to the antioxidant activity of endogenous ascorbate, which was more effective at inhibiting lipid peroxidation than the tea polyphenols and was not spared by these compounds. In contrast, when eight healthy volunteers consumed the equivalent of six cups of black tea, the resistance of their plasma to lipid peroxidation ex vivo did not increase over the next 3 h. These data suggest that, despite antioxidant efficacy in vitro, black tea does not protect plasma from lipid peroxidation in vivo. The striking discrepancy between the in vitro and ex vivo data is most likely explained by the insufficient bioavailability of tea polyphenols in humans.
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Tea polyphenols are well known for their beneficial health effects that involve their anti-carcinogenic, anti-mutagenic, anti-pathogenic and anti-oxidative properties. The main polyphenols of green tea are favan-3-ols (catechins) and their corresponding gallate compounds, which constitute about one-third of the dry weight of tea leaves. Their main ingredients are (+)-catechin (C), (−)-epicatechin (EC), (−)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG), (−)-gallocatechin gallate (GCG) and (−)-epigallocatechin gallate (EGCG). Each has slightly different biological properties. We have developed a method to simultaneously analyze all these compounds in plasma and urine. The samples were first incubated with β-d-glucuronidase and sulfatase to release the catechin residues from their corresponding conjugates for subsequent extraction by selective solid phase column, Waters Oasis HLB extraction cartridges. The extracted molecules were resolved by reversed phase HPLC and monitored by coulometric chemical detection on a CoulArray detector. All eight catechin compounds were analyzed in a single chromatogram within 25min. For plasma and urine analyses, good linearity (>0.9950) was validated in the range 10–2000 and 10–5000ng/ml, respectively. The coefficients of variance (CV) were less than 5%. Absolute recovery was greater than 85% and detection limit was 5ng/ml. The chromatogram exhibited minimal interference as a result of the highly selective solid phase extraction and CoulArray detection.
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The catechol functionality present in the catechins is responsible for the protective effects exerted by green tea against a wide range of human diseases. High-level electronic structure calculations and canonical variational transition-state theory including multidimensional tunneling corrections have allowed us to understand the key factors of the antioxidant effectiveness of the catechol group. This catechol group forms two hydrogen bonds with the two oxygen atoms of the lipid peroxyl radical, leading to a very compact reactant complex. This fact produces an extremely narrow adiabatic potential-energy profile corresponding to the hydrogen abstraction by the peroxyl radical, which makes it possible for a huge tunneling contribution to take place. So, quantum-mechanical tunneling highly increases the corresponding rate constant value, in such a way that catechins become able to trap the lipid peroxyl radicals in a dominant competition with the very damaging free-radical chain-lipid peroxidation reaction.
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To investigate the absorption and metabolism of an anticarcinogenic tea catechin, (-)-epigallocatechin-3-gallate (EGCg), in rats, a newly developed chemiluminescence-detection high-performance liquid chromatography (CL-HPLC) method was employed and the EGCg concentrations in blood plasma, liver, brain, small intestinal mucosa and colon mucosa were determined before and after EGCg administration. The recovery of EGCg, extracted consecutively with ethyl acetate and methanol, was 86.1% from plasma and 64.5-74.2% from the tissue samples. The EGCg concentrations of plasma and tissue samples from the control rat (before EGCg administration) were all below the detection limit (< 0.002 nmol/mL, 0.002 nmol/g), but 60 min after a single oral administration of EGCg (500 mg/kg body weight), the levels increased, reaching 12.3 nmol/mL in plasma, 48.4 nmol/g in liver, 0.5 nmol/g in brain, 565 nmol/g in small intestinal mucosa and 68.6 nmol/g in colon mucosa. The EGCg levels found in the tissues corresponded to 0.0003-0.45% of ingested EGCg. The results indicate that tea catechin, EGCg, is absorbed from the digestive tract, with the intestinal mucosa the most enriched of the organelles. This may explain the potent antioxidant function of EGCg in inhibiting colon mucosal phospholipid hydroperoxidation in the prevention of rat colonic carcinogenesis.
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To investigate the nature of the oxidative event that occurs during phagocytosis of retinal outer segments (ROS) by cultured human retinal pigment epithelial (RPE) cells, cells were incubated with isolated bovine ROS labeled with either the fluorescence probe carboxy-SNAFL-2 or the nonfluorescent, oxidizable probe 2',7'-dichlorodihydrofluorescein (H2DCF). The increase in fluorescence following phagocytosis was measured by a flow cytometer. Other measurements included: oxygen consumption using a Clark-type oxygen electrode, extracellular superoxide release by superoxide dismutase inhibitable lucigenin chemiluminescence, intracellular hydrogen peroxide (H2O2) production, and the effect of catalase inhibition on cellular thiobarbituric acid-reactive substances (TBARS) caused by phagocytosis. The activities of the enzymes NADPH oxidase and palmitoyl-CoA oxidase were also measured. H2DCF attached to bovine ROS was oxidized during phagocytosis with a time course suggesting oxidation subsequent to ROS uptake. Measurements of oxygen consumption showed a time-dependent increase of 10%, 4 h after ROS feeding, attributable to a doubling of the cyanide-resistant oxygen consumption. Intracellular H2O2 production also doubled 4 h after ROS phagocytosis. ROS uptake by RPE cells produced no significant extracellular superoxide, while extracellular superoxide production was readily demonstrated in a control macrophage cell line. Enzyme activity measurements showed that incubation of RPE cells with ROS doubled catalase activity without affecting superoxide dismutase or glutathione peroxidase activities. Inhibition of catalase during ROS uptake increased TBARS by 66%. Other enzyme activity measurements showed that human RPE cells possess both NADPH oxidase and palmitoyl-CoA oxidase activities. We conclude that ROS phagocytosis subjects RPE cells to an oxidative event on the same order of magnitude as measured in a macrophage. The event is not an extracellular macrophage-type respiratory burst and may be due to intracellular H2O2 resulting from an NADPH oxidase in the phagosome or from beta-oxidation of ROS lipids in peroxisomes. Irrespective of case, the enzyme catalase appears to be essential in protecting the RPE cell against reactive oxygen species produced during phagocytosis.
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This work reports a differential effect of ultraviolet A (UVA) irradiation on the three major cytoskeletal structures, actin and vimentin filaments and microtubules of lens cells in primary culture. The effect on cells from lens of the skate (a bottom-dwelling marine elasmobranch) was compared with that on rabbit lens, in order to assess UVA sensitivity as a function of exposure to these wavelengths in the native habitat. Exposure intervals of irradiation time up to 6 hours were selected, at fluences from 13.5 to 54.4 J/cm2 and at 365 +/- 45 nm wavelength, to represent mild to moderate physiological levels. Cultures were fixed and processed with anti-alpha-tubulin-FITC and rhodamine phalloidin, or with anti-vimentin FITC and rhodamine phalloidin conjugates. With epifluorescence microscopy, it was found that microtubules were most sensitive to UVA irradiation (in depolymerizing), followed by actin, with vimentin hardly at all affected. Irradiation for 6 hours followed by incubation for 3 days in fresh medium showed no recovery of actin but good recovery of microtubule organizing centers, followed by mitosis in many (rabbit) cells. Skate cells were more sensitive and showed no recovery. In view of the role of cytoskeletal elements in intracellular structure, cell division and transport, their disruption supports the hypothesis that UVA may damage lens epithelial cells in vivo so as to contribute to cataract formation. In addition, the data suggest that the lenses of animals exposed to sunlight require effective cytoskeletal repair mechanisms to avoid loss of function.
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Tea polyphenols-including (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin (EC)-are believed to be responsible for the beneficial effects of tea. This study was conducted to investigate the absorption, distribution, and elimination of EGCG, EGC, and EC in rats after administration of decaffeinated green tea (DGT). For comparison, pure EGCG was also studied. The plasma and tissue levels of EGCG, EGC, and EC were quantified by HPLC, and the results were analyzed by the PCNONLIN program. Following intravenous injection of DGT (25 mg/kg), the plasma concentration-time curves of EGCG, EGC, and EC were fitted in a two-compartment model. The beta-elimination half-lives (t1/2beta) were 212, 45, and 41 min for EGCG, EGC, and EC, respectively; the clearances were 2.0, 7.0, and 13.9 ml x min/kg, and the apparent distribution volumes (V(d)) were 1.5, 2.1, and 3.6 dl/kg. When pure EGCG (10 mg/kg) was given, however, a shorter t1/2beta (135 min), a larger clearance (72.5 ml x min/kg), and a larger V(d) (22.5 dl/kg) for EGCG were observed, suggesting that other components in DGT could affect the plasma concentration and elimination of EGCG. After intragastric administration of DGT (200 mg/kg), approximately 13.7% of EGC and 31.2% of EC were shown in the plasma, but only 0.1% of EGCG was bioavailable as judged by the ratio of AUC(i.g.)/AUC(i.v.). After intravenous administration of DGT (25 mg/kg), the level of EGCG was found to be the highest in the intestine samples, and the intestinal EGCG level declined with a t1/2 of 173 min. The highest levels of EGC and EC were observed in the kidney, and the levels declined rapidly with t1/2 of 29 and 28 min, respectively. The AUC of EGCG in the intestine was 4-fold higher than that in the kidney, but the AUCs of EGC and EC in the intestine were similar to those in the kidney. The liver and lung levels of EGCG, EGC, and EC were generally lower than those in the intestine and the kidney. The distribution results suggest that EGCG is mainly excreted through bile, and that EGC and EC are excreted through both the bile and urine.
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The increasing recognition of green tea and tea polyphenols as cancer preventives has created a need for a study of their bioavailability. For this purpose, we synthesized [3H] (-)-epigallocatechin gallate ([3H]EGCG) with a specific activity of 48.1 GBq/mmol and directly administered the solution into the stomachs of CD-1 female or male mice. Radioactivity in the digestive tract, various organs, blood, urine and feces was measured with an oxidizer at various times after administration and significant radioactivity was found in the previously reported target organs of EGCG and green tea extract (digestive tract, liver, lung, pancreas, mammary gland and skin), as well as other organs (brain, kidney, uterus and ovary and testes) in both sexes. Incorporation of radioactivity in the cells was confirmed by microautoradiography. Within 24 h, 6.6 (females) and 6.4% (males) of total administered radioactivity was excreted in the urine and 37.7 and 33.1% in feces. HPLC analysis of urine from both sexes revealed that 0.03-0.59% of administered [3H]EGCG, along with at least five metabolites, was excreted. In addition, we found that a second, equal administration to female mice after a 6 h interval enhanced tissue levels of radioactivity in blood, brain, liver, pancreas, bladder and bone 4-6 times above those after a single administration. These results suggest that frequent consumption of green tea enables the body to maintain a high level of tea polyphenols and this paper is the first pharmacological evidence of a wide distribution of [3H]EGCG in mouse organs, indicating a similar wide range of target organs for cancer prevention in humans.
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This chapter has outlined methods to assess lipid peroxidation associated with oxidant injury in vivo by quantifying concentrations of free F2-IsoPs in biological fluids and levels of F2-IsoPs esterified in tissue lipids. The mass spectrometric assay described herein is highly precise and accurate. A potential shortcoming with this approach is that it requires expensive instrumentation, i.e., a mass spectrometer. However, several immunoassays for an F2-IsoP, 8-iso-PGF2 alpha, have become available from commercial sources. At this time, the accuracy and reliability of these assay for quantifying F2-IsoPs in biological fluids has not been fully validated by mass spectrometry. If these immunoassays prove to be a reliable measure of F2-IsoPs, however, this should greatly expand the use of F2-IsoPs to assess oxidant stress. In conclusion, studies carried out over the past several years have shown that measurement of F2-IsoPs has overcome many of the limitations associated with other methods to assess oxidant status, especially when applied to the measurement of oxidant stress in vivo in humans. Therefore, the quantification of F2-IsoPs represents an important advance in our ability to assess the role of oxidant stress and lipid peroxidation in human disease.
Article
The isoprostanes (IsoPs) are a series of novel prostaglandin (PG)-like compounds generated from the free radical-catalyzed peroxidation of arachidonic acid. The first series of IsoPs characterized contained F-type prostane rings analogous to PGF2alpha. One F-ring IsoP, 15-F2t-IsoP (8-iso-PGF2alpha) has been shown to be formed in abundance in vivo and to exert potent biological activity. As a means to assess the endogenous production of this compound, we developed a method to quantify the major urinary metabolite of 15-F2t-IsoP, 2,3-dinor-5,6-dihydro-15-F2t-IsoP (2,3-dinor-5, 6-dihydro-8-iso-PGF2alpha), by gas chromotography/negative ion chemical ionization mass spectrometry. This metabolite was chemically synthesized and converted to an 18O2-labeled derivative for use as an internal standard. After purification, the compound was analyzed as a pentafluorobenzyl ester trimethylsilyl ether. Precision of the assay is +/-4% and accuracy is 97%. The lower limit of sensitivity is approximately 20 pg. Levels of the urinary excretion of this metabolite in 10 normal adults were found to be 0. 39 +/- 0.18 ng/mg creatinine (mean +/- 2 SD). Substantial elevations in the urinary excretion of the metabolite were found in situations in which IsoP generation is increased and antioxidants effectively suppressed metabolite excretion. Levels of 2,3-dinor-5, 6-dihydro-15-F2t-IsoP were not affected by cyclooxygenase inhibitors. Thus, this assay provides a sensitive and accurate method to assess endogenous production of 15-F2t-IsoP as a means to explore the pathophysiological role of this compound in human disease.
Article
The purpose of the present experiments was to evaluate the contribution of the glutamate-glutamine cycle in retinal glial (Müller) cells to photoreceptor cell synaptic transmission. Dark-adapted isolated rat retinas were superfused with oxygenated bicarbonate-buffered media. Recordings were made of the b-wave of the electroretinogram as a measure of light-induced photoreceptor to ON-bipolar neuron transmission. L-methionine sulfoximine (1-10 mM) was added to superfusion media to inhibit glutamine synthetase, a Müller cell specific enzyme, by more than 99% within 5-10 min, thereby disrupting the conversion of glutamate to glutamine in the Müller cells. Threo-hydroxyaspartic acid and D-aspartate were used to block glutamate transporters. The amplitude of the b-wave was well maintained for 1-2 h provided 0.25 mM glutamate or 0.25 mM glutamine was included in the media. Without exogenous glutamate or glutamine the amplitude of the b-wave declined by about 70% within 1 h. Inhibition of glutamate transporters led to a rapid (2-5 min) reversible loss of the b-wave in the presence and absence of the amino acids. In contrast, inhibition of glutamine synthetase did not alter significantly either the amplitude of the b-wave in the presence of glutamate or glutamine or the rate of decline of the b-wave found in the absence of these amino acids. Excellent recovery of the b-wave was found when 0.25 mM glutamate was resupplied to L-methionine sulfoximine-treated retinas. The results suggest that in the isolated rat retina uptake of released glutamate into photoreceptors plays a more important role in transmitter recycling than does uptake of glutamate into Müller cells and its subsequent conversion to glutamine.
Article
8-Iso-PGF2alpha is formed in vivo by non-enzymatic free radical catalysed oxidation of arachidonic acid. Urinary measurement of this compound has previously been shown to reflect the oxidative stress of the body in human and animal studies. To investigate the normal excretion rate and a possible diurnal variation of 8-iso-PGF2alpha excretion in humans urinary samples were collected from ten healthy volunteers of both sexes at different times during a day and as a 24-h urine sample. The samples were analyzed by a newly developed radioimmunoassay with a specific antibody against free 8-iso-PGF2alpha. There was no diurnal variation in the urinary levels of 8-iso-PGF2alpha during the day in this study. Neither was there any statistically significant difference between the 8-iso-PGF2alpha levels at any time of the day or in the morning urine samples compared to the 24-h urine samples. In conclusion, all urine samples collected at any time of the day, preferably a morning urine sample (representative urine from 6-8 hours), can thus be used to obtain a reliable and adequate value of the amount of the 8-iso-PGF2alpha excretion in urine in healthy individuals.
Article
In this article we present results from the Resair 2 study in which we tested whether room air is more efficient than 100% oxygen in newborn resuscitation. Eleven participating centres in Egypt, Estonia, India, Norway, Philippines, and Spain recruited 609 infants who needed resuscitation at birth; of these, 288 were resuscitated with room air and 321 with 100% oxygen. There were no differences between the two groups with regard to outcome. One minute Apgar scores were significantly lower in the oxygen group than in the room air group. Median time to first breath was significantly delayed with 24 seconds in the oxygen group compared with the room air group. It seems that 100% oxygen depresses ventilation in newborn infants. Room air is as safe and efficient as 100% oxygen at least in most cases of newborn resuscitation. Further studies confirming these results are needed before new resuscitation routines are implemented.
Article
After oral administration of (-)-epigallocatechin gallate (EGCg) to rats, its biliary metabolites were examined. Although a large part of the biliary metabolites was found to exist in conjugated forms, it was difficult to separate the conjugated forms. Thus the free form of biliary metabolites was prepared by beta-glucuronidase/sulfatase treatment and was purified by HPLC. Six compounds purified were subjected to FABeta-MS and NMR analyses. The six metabolites thus obtained were shown to be EGCg, 3'-O-methyl-EGCg, 4'-O-methyl-EGCg, 3' '-O-methyl-EGCg, 4' '-O-methyl-EGCg, and 4',4' '-di-O-methyl-EGCg, respectively. The six EGCg metabolites and their conjugates excreted during a 4-h period were estimated to be roughly 0.1% and 3.3% of the administered EGCg, respectively. In addition, 4' '-O-methyl-EGCg and 4',4' '-di-O-methyl-EGCg were estimated to exist only in the sulfate form, but the other four metabolites existed in both glucuronide (and/or sulfoglucuronide) and sulfate forms.
Article
Green tea has been shown to exhibit cancer-preventive activities in preclinical studies. Its principal active components include epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin (EC), and epicatechin gallate, of which EGCG is the most abundant and possesses the most potent antioxidative activity. We performed a Phase I pharmacokinetic study to determine the systemic availability of green tea catechins after single oral dose administration of EGCG and Polyphenon E (decaffeinated green tea catechin mixture). Twenty healthy subjects (five subjects/dose level) were randomly assigned to one of the dose levels (200, 400, 600, and 800 mg based on EGCG content). All subjects were randomly crossed-over to receive the two catechin formulations at the same dose level. Blood and urine samples were collected for up to 24 h after oral administration of the study medication. Tea catechin concentrations in plasma and urine samples were determined using high-performance liquid chromatography with the coulometric electrode array detection system. After EGCG versus Polyphenon E administration, the mean area under the plasma concentration-time curves (AUC) of unchanged EGCG were 22.5 versus 21.9, 35.4 versus 52.2, 101.9 versus 79.7, and 167.1 versus 161.4 min x microg/ml at the 200-, 400-, 600-, and 800-mg dose levels, respectively. EGC and EC were not detected in plasma after EGCG administration and were present at low/undetectable levels after Polyphenon E administration. High concentrations of EGC and EC glucuronide/sulfate conjugates were found in plasma and urine samples after Polyphenon E administration. There were no significant differences in the pharmacokinetic characteristics of EGCG between the two study medications. The AUC and maximum plasma concentration (Cmax) of EGCG after the 800-mg dose of EGCG were found to be significantly higher than those after the 200- and 400-mg dose. The AUC and Cmax of EGCG after the 800-mg dose of Polyphenon E were significantly higher than those after the three lower doses. We conclude that the two catechin formulations resulted in similar plasma EGCG levels. EGC and EC were present in the body after the Polyphenon E administration; however, they were present predominantly in conjugated forms. The systemic availability of EGCG increased at higher doses, possibly due to saturable presystemic elimination of orally administered green tea polyphenols.
Article
Oxygen is a toxic agent and a critical approach regarding its use during resuscitation at birth is developing. Animal data indicate that room air is efficient for newborn resuscitation. Three clinical studies have established that normal ventilation is delayed after oxygen resuscitation. Oxidative stress is augmented for several weeks in infants exposed to oxygen at birth -- the long-term implications of these observations remain unclear. There are limited data regarding the use of room air during complicated resuscitations, i.e. in meconium aspiration, the severely asphyxiated infant and in the preterm infant. Thus, it is necessary to continue ongoing rigorous examination of the long-accepted practice of oxygen administration during neonatal resuscitation.
Article
We previously reported the discovery of prostaglandin F2-like compounds (F2-isoprostanes) formed by nonenzymatic free-radical-induced peroxidation of arachidonic acid. Quantification of F2-isoprostanes has proven to be a major advance in assessing oxidative stress status in vivo. Central in the pathway of formation of isoprostanes are prostaglandin H2-like endoperoxides, which also undergo rearrangement in vivo to form E-ring, D-ring, and thromboxane-ring compounds. E2- and D2-isoprostanes also undergo dehydration in vivo to form reactive cyclopentenone A2- and J2-isoprostanes, which are susceptible to Michael addition reactions with thiols. Recently, we described the formation of highly reactive gamma-ketoaldehydes (now termed isoketals) as products of isoprostane endoperoxide rearrangement which readily adduct to lysine residues on proteins and induce cross-links at rates that far exceed other aldehyde products of lipid peroxidation. Isoprostane-like compounds (neuroprostanes) and isoketal-like compounds (neuroketals) are formed from oxidation of docosahexaenoic acid, which is enriched in the brain, and measurement of neuroprostanes may provide a unique marker of oxidative neuronal injury.
Article
After water, tea is the most popular beverage and is consumed by two thirds of the world's population. Three types of tea are available; they vary in the processes of drying and fermentation. Besides black tea, which is the most prevalent form (78%), green tea (20%) and oolong (2%) are produced. The
Article
Catechins levels in organ tissues, particularly liver, determined by published methods are unexpectedly low, probably due to the release of oxidative enzymes, metal ions and reactive metabolites from tissue cells during homogenization and to the pro-oxidant effects of ascorbic acid during sample processing in the presence of metal ions. We describe a new method for simultaneous analysis of eight catechins in tissue: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-catechin gallate (CG), (-)-epicatechin gallate (ECG), (-)-gallocatechin gallate (GCG) and (-)-epigallocatechin gallate (EGCG) (Fig. 1). The new extraction procedure utilized a methanol/ethylacetate/dithionite (2:1:3) mixture during homogenization for simultaneous enzyme precipitation and antioxidant protection. Selective solid phase extraction was used to remove most interfering bio-matrices. Reversed phase HPLC with CoulArray detection was used to determine the eight catechins simultaneously within 25 min. Good linearity (>0.9922) was obtained in the range 20-4000 ng/g. The coefficients of variance (CV) were less than 5%. Absolute recovery ranged from 62 to 96%, accuracy 92.5 +/- 4.5 to 104.9 +/- 6%. The detection limit was 5 ng/g. This method is capable for determining catechins in rat tissues of liver, brain, spleen, and kidney. The method is robust, reproducible, with high recovery, and has been validated for both in vitro and in vivo sample analysis.
Article
A2-PE is a pigment that forms as a byproduct of the visual cycle, its synthesis from all-trans-retinal and phosphatidylethanolamine occurring in photoreceptor outer segments. A2-PE is deposited in retinal pigment epithelial (RPE) cells secondary to phagocytosis of shed outer segment membrane and it undergoes hydrolysis to generate the RPE lipofuscin fluorophores, A2E, iso-A2E and other minor cis-isomers of A2E. We have demonstrated that A2-PE can initiate photochemical processes that involve the oxidation of A2-PE and that, by analogy with A2E are likely to include the formation of reactive moieties. We also show that potential sources of protection against the photooxidation of A2-PE are the lipid-soluble carotenoids zeaxanthin and lutein (xanthophylls), that constitute the yellow pigment of the macula. Irradiation of A2-PE in the presence of lutein or zeaxanthin suppressed A2-PE photooxidation and in experiments in which we compared the antioxidant capability of zeaxanthin and lutein to alpha-tocopherol, the carotenoids were more potent. Additionally, the effect with zeaxanthin was consistently more robust than with lutein and when alpha-tocopherol was combined with either carotenoid, the outcome was additive. Lutein, zeaxanthin and alpha-tocopherol were all efficient quenchers of singlet oxygen. We have also shown that lutein and zeaxanthin can protect against A2-PE/A2E photooxidation without appreciable consumption of the carotenoid by chemical reaction. This observation contrasts with the pronounced susceptibility of A2E and A2-PE to photooxidation and is of interest since lutein, zeaxanthin, A2E and A2-PE all have conjugated systems of carbon-carbon double bonds terminating in cyclohexenyl end-groups. The structural features responsible for the differences in quenching mechanisms are discussed. It has long been suspected that macular pigment protects the retina both by filtering high-energy blue light and by serving an antioxidant function. Evidence presented here suggests that the photochemical reactions against which lutein and zeaxanthin protect, may include those initiated by the A2-PE. Quantitative HPLC analysis revealed that in eyecups of C57BL/6J and BALB/cByJ mice, levels of A2-PE were several fold greater than the cleavage product, A2E. Taken together, these results may have implications with respect to the involvement of A2-PE formation in mechanisms underlying blue light-induced photoreceptor cell damage and may be significant to retinal degenerative disorders, such as those associated with ABCA4 mutations, wherein there is a propensity for increased A2-PE synthesis.
Article
The purpose of this study is to provide evidence that free radical damage is a component of retinal ischemia-reperfusion (I/R) injury, and to determine whether alpha-tocopherol, gamma-tocopherol and d-alpha-tocopherol polyethylene glycol 1000 succinate (TPGS) can protect the retina from this injury. The right eyes of 40 male guinea pigs weighing 500-600 g were used. The animals were randomly assigned to group 1 (control), group 2 (I/R), group 3 (I/R plus alpha-tocopherol), group 4 (I/R plus gamma-tocopherol) and group 5 (I/R plus TPGS). Groups 3, 4 and 5 received four subcutaneous injections at six-hour intervals for total dosage of 800 IU/kg alpha-tocopherol, 1000 IU/kg gamma-tocopherol and 750 IU/kg TPGS, respectively. The first dose of each substance was administered 5 minutes before retinal ischemia. Retinal ischemia was induced for 90 minutes, then followed by reperfusion for 24 hours. Injections of three substances were repeated at 6, 12 and 18 hours during reperfusion. The animals were killed at 24 hours of reperfusion. Sagittal sections of 4 microm were cut and stained with hematoxylin and eosin for light microscopic evaluation. The average thickness (edema) of the inner plexiform layer for each eye was measured in sagittal sections near the optic nerve and expressed in microns. All the three substances showed statistically significant protection against the formation of retinal edema during ischemia-reperfusion injury. The mean thickness of the inner plexiform layer were 15.0, 25.44, 19.81, 21.38 and 20.88 microm in control, I/R, I/R plus alpha-tocopherol, I/R plus gamma-tocopherol and I/R plus TPGS groups, respectively. The results showed that the thickness of the inner plexiform layer in group 1 (control) was significantly lower than the other groups (p<0.001). The inner plexiform layer was thicker in the I/R group than with I/R plus alpha-tocopherol (p<0.001), I/R plus gamma-tocopherol (p<0.001) and I/R plus TPGS (p<0.01). The inner plexiform layer was not thicker in the I/R plus TPGS group than in the I/R plus alpha-tocopherol and I/R plus gamma-tocopherol groups. Compared to the I/R plus alpha-tocopherol group, the inner plexiform layer was significantly thicker in the I/R plus gamma-tocopherol group (p<0.01). The results from these experiments indicate that vitamin E forms have protective effects on the retina during retinal ischemia-reperfusion injury, but, the effects of alpha-tocopherol and TPGS appear to be much greater than that of gamma-tocopherol.
Article
We carried out a pharmacokinetic study to determine the levels and profiles of catechins in pregnant rats and their fetuses after ingestion of green tea extract (GTE). We measured total catechin levels after enzyme digestions. Dams, at 15.5 days of gestation, were fed with GTE and catechins were measured in the maternal plasma, placenta, and fetus 0, 0.5, 1, 2, 3, 5, 8, 10, 12, 16, and 20 h after maternal GTE intake. The pharmacokinetic changes were analyzed by non compartmental models. We found that maternal plasma concentrations of catechins were about 10 times higher than in placenta and 50-100 times higher than in the fetus. AUC and Cmax levels of (-)-epicatechin (EC) were the highest in plasma while the levels of (-)-epigallocatechin gallate (EGCG) were the highest in the placenta and the fetus. The exposure level of catechin derivatives was higher than the gallate derivatives in maternal plasma after normalization but reversed in the placenta and fetus. The absorption of epi-isomers in plasma was found to be more favorable than their non epi-isomer counterparts. EGCG had the highest level of exposure (AUC) and the highest Cmax in the fetus, implying it may have potential for in utero antioxidant protection.