Green tea and its polyphenolic catechins: medicinal uses in cancer and noncancer applications

Concise synthesis of catechin probes enabling analysis and imaging of EGCg

A concise synthesis of APDOEGCg (3) was accomplished. Due to the reactivity of its amine group, the compound could be easily converted to the fluorescein probe 21 and immunogen probe 22 efficiently. We then demonstrated the usefulness of the probes for imaging studies and the generation of antibodies.

Strategies for the discovery of anti-aging compounds

IMPORTANCE OF THE FIELD

Life expectancy has increased across the globe and the number of aged people is increasing rapidly. With the rise in the average age of people, the prevalence of age related pathologies has also increased and thus the strategies to find anti-aging molecules assume significance. Anti-aging basically concerns the prevention or delaying the alterations taking place as a function of age which are manifested as age-associated illnesses.

AREAS COVERED IN THIS REVIEW

This review covers anti-aging strategies involving supplementation of dietary antioxidants such as polyphenols, vitamins E and C, lipoic acid, acetyl carnitine, carnosine and cysteine along with the application of mammalian target of rapamycin inhibitors and plasma membrane redox system activators. It also presents the use of different hormone supplementation, for example, melatonin, dehydroepiandrosterone, growth hormone and sex hormones as a tool against aging. The use of caloric restriction and calorie restriction mimetics as an anti-aging intervention is also reviewed.

WHAT THE READER WILL GAIN

The concept, use and efficacy of different anti-aging approaches.

TAKE HOME MESSAGE

Despite a lot of research and sustained ongoing efforts, finding a viable anti-aging therapy which can extend the maximum human lifespan remains elusive. However, several interventions aimed towards a longer healthy life seem promising.

Effects of cellulase from Aspergillus niger and solvent pretreatments on the extractability of organic green tea waste

As green tea is being consumed in larger amounts, more green tea waste is being produced. Following extraction, several bioactive compounds may exist in the waste including polyphenols and amino acids. It was found that an Aspergillus niger cellulase treatment of green tea waste increased the extractability of various nutritional and functional components after pretreatments with various extraction solvents such as cold water (CW), hot water (HW), sulfuric acid (SA), hydrochloric acid (HA), and methanol (Me). After the residue was treated with cellulase from Aspergillus niger, the amounts of polyphenols, total catechins, and reducing sugars in the HW extract were increased by 64.6, 941.2, and 350.9%, respectively. In particular, levels of epigallocatechin, epicatechin, and gallic acid were significantly enhanced compared to those in the nontreated control. However, protein extraction was not significantly affected, and cellulase treatment was not more efficient for caffeine extraction compared to phenolic extraction. Among the four extraction solvents, HW and SA showed relatively higher extractabilities as compared to the other groups (CW, HA, and Me). These results indicate that cellulase from A. niger can increase the extractability of green tea waste when combined with certain solvent pretreatments. Consequently, the residual functional compounds and essential nutrients from cellulase-treated green tea waste have the potential to be applied in the production of new functional foods.

Green tea polyphenols potentiate the action of nerve growth factor to induce neuritogenesis: possible role of reactive oxygen species

Exogenously administered nerve growth factor (NGF) repairs injured axons, but it does not cross the blood-brain barrier. Thus, agents that could potentiate the neuritogenic ability of endogenous NGF would be of great utility in treating neurological injuries. Using the PC12 cell model, we show here that unfractionated green tea polyphenols (GTPP) at low concentrations (0.1 μg/ml) potentiate the ability of low concentrations of NGF (2 ng/ml) to induce neuritogenesis at a level comparable to that induced by optimally high concentrations of NGF (50 ng/ml) alone. In our experiments, GTPP by itself did not induce neuritogenesis or increase immunofluorescent staining for β-tubulin III; however, it increased expression of mRNA and proteins for the neuronal markers neurofilament-L and GAP-43. Among the polyphenols present in GTPP, epigallocatechin-3-gallate (EGCG) alone appreciably potentiated NGF-induced neurite outgrowth. Although other polyphenols present in GTPP, particularly epigallocatechin and epicatechin, lack this activity, they synergistically promoted this action of EGCG. GTPP also induced an activation of extracellular signal-regulated kinases (ERKs). PD98059, an inhibitor of the ERK pathway, blocked the expression of GAP-43. K252a, an inhibitor of TrkA-associated tyrosine kinase, partially blocked the expression of these genes and ERK activation. Antioxidants, catalase (cell-permeable form), and N-acetylcysteine (both L and D-forms) inhibited these events and abolished the GTPP potentiation of NGF-induced neuritogenesis. Taken together, these results show for the first time that GTPP potentiates NGF-induced neuritogenesis, likely through the involvement of sublethal levels of reactive oxygen species, and suggest that unfractionated GTPP is more effective in this respect than its fractionated polyphenols.

Flavonoids as protein kinase inhibitors for cancer chemoprevention: direct binding and molecular modeling

Protein kinases play crucial roles in the regulation of multiple cell signaling pathways and cellular functions. Deregulation of protein kinase function has been implicated in carcinogenesis. The inhibition of protein kinases has emerged as an important target for cancer chemoprevention and therapy. Accumulated data revealed that flavonoids exert chemopreventive effects through acting at protein kinase signaling pathways, more than as conventional hydrogen-donating antioxidants. Recent studies show that flavonoids can bind directly to some protein kinases, including Akt/protein kinase B (Akt/PKB), Fyn, Janus kinase 1 (JAK1), mitogen-activated protein kinase kinase 1 (MEK1), phosphoinositide 3-kinase (PI3K), mitogen-activated protein (MAP) kinase kinase 4 (MKK4), Raf1, and zeta chain-associated 70-kDa protein (ZAP-70) kinase, and then alter their phosphorylation state to regulate multiple cell signaling pathways in carcinogenesis processes. In this review, we report recent results on the interactions of flavonoids and protein kinases, especially their direct binding and molecular modeling. The data suggest that flavonoids act as protein kinase inhibitors for cancer chemoprevention that were thought previously as conventional hydrogen-donating antioxidant. Moreover, the molecular modeling data show some hints for creating natural compound-based protein kinase inhibitors for cancer chemoprevention and therapy.

Green tea improves metabolic biomarkers, not weight or body composition: a pilot study in overweight breast cancer survivors

BACKGROUND

Overweight status after breast cancer treatment may increase a woman's risk for recurrent disease and/or early onset cardiovascular disease. Green tea has been proposed to promote weight loss and favourably modify glucose, insulin and blood lipids. This pilot study tested the effect of daily decaffeinated green tea consumption for 6 months on weight and body composition, select metabolic parameters and lipid profiles in overweight breast cancer survivors.

METHODS

The effect of daily decaffeinated green tea intake on weight, body composition and changes in resting metabolic rate, energy intake, glucose, insulin, homeostasis model assessment--insulin resistance (HOMA-IR) and lipids was evaluated in overweight breast cancer survivors. Participants had a mean weight of 80.2 kg; body mass index (BMI) 30.1 kg m⁻²; and body fat 46.4%. Participants (n = 54) were randomised to 960 mL of decaffeinated green or placebo tea daily for 6 months.

RESULTS

Mean (SD) tea intake among study completers (n = 39) was 5952 (1176) mL week⁻¹ and was associated with a significant reduction in energy intake (P = 0.02). Change in body weight of -1.2 kg (green tea) versus +0.2 kg (placebo) suggests a weight change effect, although this was not statistically significant. Decaffeinated green tea intake was associated with elevated high-density lipoprotein (HDL) levels (P = 0.003) and nonsignificant improvements in the HDL/LDL ratio and HOMA-IR (-1.1 ± 5.9: green tea; +3.2 ± 7.2: herbal).

CONCLUSIONS

Intake of decaffeinated green tea for 6 months was associated with a slight reduction in body weight and improved HDL and glucose homeostasis in overweight breast cancer survivors.

Isoquercitrin is the most effective antioxidant in the plant Thuja orientalis and able to counteract oxidative-induced damage to a transformed cell line (RGC-5 cells)

The shrub Thuja orientalis is extensively used as a herbal medicine in Korea and China. In the present study extracts of the plant were subjected to fractionation and purification, with seven compounds (myricitrin, isoquercitrin, hypoletin-7-O-β-D-xylopyranoside, quercitrin, kaempferin, kaempferol, and amentoflavone) being isolated. Of these seven compounds, isoquercitrin was found to be the most effective at attenuating the death of RGC-5 cells in culture caused by exposure to hydrogen peroxide (H(2)O(2)). It was found that an insult of H(2)O(2) to RGC-5 cells caused them to die by apoptosis, demonstrated not only by staining dead cells for phosphatidylserine but also by the up-regulation (cleaved PARP, AIF, p53) and down-regulation (Bcl-2) of proteins associated with apoptosis and survival. Subsequent studies showed that isoquercitrin acts as a powerful antioxidant. It scavenges ROS generally as demonstrated by staining of cultures as well as the generation of individual radical species (H(2)O(2), OH* and O(2)(*-)). Moreover, isoquercitrin reduced the depletion of glutathione (GSH) caused by elevation of specific radical species (H(2)O(2), OH* and O(2)(*-)) in RGC-5 cells in culture and blunted the decrease in catalase and glutathione peroxidase 1 (Gpx-1) caused by exposure of RGC-5 cells to H(2)O(2). Furthermore, isoquercitrin potently attenuated the lipid peroxidation of rat brain homogenates initiated by nitric oxide, with an IC(50) value of 1.04 μM. Since isoquercitrin can be tolerated when taken orally it is suggested that this substance might reach the retina and therefore be potentially useful for treating glaucoma, in which oxidative stress is thought to play a major role in the demise of retinal ganglion cells.

Beneficial effects of green tea: a literature review

The health benefits of green tea for a wide variety of ailments, including different types of cancer, heart disease, and liver disease, were reported. Many of these beneficial effects of green tea are related to its catechin, particularly (-)-epigallocatechin-3-gallate, content. There is evidence from in vitro and animal studies on the underlying mechanisms of green tea catechins and their biological actions. There are also human studies on using green tea catechins to treat metabolic syndrome, such as obesity, type II diabetes, and cardiovascular risk factors.Long-term consumption of tea catechins could be beneficial against high-fat diet-induced obesity and type II diabetes and could reduce the risk of coronary disease. Further research that conforms to international standards should be performed to monitor the pharmacological and clinical effects of green tea and to elucidate its mechanisms of action.

Beneficial storage effects of epigallocatechin-3-o-gallate on the articular cartilage of rabbit osteochondral allografts

A fresh osteochondral allograft is one of the most effective treatments for cartilage defects of the knee. Despite the clinical success, fresh osteochondral allografts have great limitations in relation to the short storage time that cartilage tissues can be well-preserved. Fresh osteochondral grafts are generally stored in culture medium at 4 degrees C. While the viability of articular cartilage stored in culture medium is significantly diminished within 1 week, appropriate serology testing to minimize the chances for the disease transmission requires a minimum of 2 weeks. (-)-Epigallocatechin-3-O-gallate (EGCG) has differential effects on the proliferation of cancer and normal cells, thus a cytotoxic effect on various cancer cells, but a cytopreservative effect on normal cells. Therefore, a storage solution containing EGCG might extend the storage duration of articular cartilages. Rabbit osteochondral allografts were performed with osteochondral grafts stored at 4 degrees C in culture medium containing EGCG for 2 weeks and then the clinical effects were examined with macroscopic and histological assessment after 4 weeks. The cartilaginous structure of an osteochondral graft stored with EGCG was well-preserved with high cell viability and glycosaminoglycan (GAG) content of the extracellular matrix (ECM). After an osteochondral allograft, the implanted osteochondral grafts stored with EGCG also provided a significantly better retention of the articular cartilage with viability and metabolic activity. These data suggest that EGCG can be an effective storage agent that allows long-term preservation of articular cartilage under cold storage conditions.

Protective activity of Theobroma cacao L. phenolic extract on AML12 and MLP29 liver cells by preventing apoptosis and inducing autophagy

Theobroma cacao L. is known to have potential cardiovascular and cancer chemopreventive activities because of its high content of phenolic phytochemicals and their antioxidant capacities. In this work, we show for the first time that cocoa inhibits drug-triggered liver cytotoxicity by inducing autophagy. Phenolic-rich extracts of both unroasted and roasted cocoa prevented Celecoxib-induced cell viability inhibition in MLP29 liver cells because of the accumulation of G1 cells and cell death. Death prevented by cocoa had hallmarks of apoptosis such as the sub-G1 peak at flow cytometry and activation of Bax expression, together with down-regulation of Bcl-2, released cytochrome c in the cytosol with activation of Caspase 3, indicating that components of the apoptotic pathway such as Bax or upstream are major targets of cocoa phytochemicals. The protective effect of cocoa against liver cytotoxicity by Celecoxib was probably accounted for by inducing the autophagic process, as shown by enhanced Beclin 1 expression and accumulation of monodansylcadaverine in autolysosomes. This fact suggests that apoptosis was prevented by inducing autophagy. Finally, considering all these findings, we suggest that cocoa can be added to the list of natural chemopreventive agents whose potential in hepatopathy prevention and therapy should be evaluated.

Hepatotoxicity of high oral dose (-)-epigallocatechin-3-gallate in mice

The tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) has been studied for chronic disease preventive effects, and is marketed as part of many dietary supplements. However, case-reports have associated the use of green tea-based supplements with liver toxicity. We studied the hepatotoxic effects of high dose EGCG in male CF-1 mice. A single dose of EGCG (1500 mg/kg, i.g.) increased plasma alanine aminotransferase (ALT) by 138-fold and reduced survival by 85%. Once-daily dosing with EGCG increased hepatotoxic response. Plasma ALT levels were increased 184-fold following two once-daily doses of 750 mg/kg, i.g. EGCG. Moderate to severe hepatic necrosis was observed following treatment with EGCG. EGCG hepatotoxicity was associated with oxidative stress including increased hepatic lipid peroxidation (5-fold increase), plasma 8-isoprostane (9.5-fold increase) and increased hepatic metallothionein and gamma-histone 2AX protein expression. EGCG also increased plasma interleukin-6 and monocyte chemoattractant protein-1. Our results indicate that higher bolus doses of EGCG are hepatotoxic to mice. Further studies on the dose-dependent hepatotoxic effects of EGCG and the underlying mechanisms are important given the increasing use of green tea dietary supplements, which may deliver much higher plasma and tissue concentrations of EGCG than tea beverages.

Prevention of oxidative DNA damage in inner organs and lymphocytes of rats by green tea extract

BACKGROUND

Consumption of green tea (GT) is associated with decreased incidences of specific forms of cancer in humans and it was postulated that its antioxidant (AO) properties may account for these effects. The evidence for AO effects of GT is mainly based on the results from in vitro experiments and on animal studies in which protection against chemically induced damage was monitored.

AIM OF THE STUDY

The goal of the study was the investigation of the prevention of strand breaks and DNA migration attributable to endogenous oxidation of bases by GT extract (GTE) in inner organs and lymphocytes of untreated rats. In addition, immunological parameters and biochemical markers were monitored.

METHODS

DNA migration was measured in hepatocytes, colonocytes and lymphocytes after consumption of a low (1.3 mg/kg bw per day, 5 days) and a high dose (6.5 mg/kg bw per day, 5 days) of GTE in COMET assays (n = 5 animals per group). In addition, immunological parameters (TNF-alpha, IFN-gamma, IL-4 and IL-10), the total AO capacity and oxidized low-density lipoproteins were determined in plasma.

RESULTS

No evidence for reduction in DNA damage was found with a lower dose, whereas with the higher dose, reduction in DNA migration attributable to formamidopyrimidine-DNA-glycosylase sensitive lesions (oxidized purines) and endonuclease III-sensitive sites (oxidized pyrimidines) (58 and 73%) was observed in lymphocytes; also, in colonocytes (reduction in FPG-sensitive sites by 46%) and hepatocytes (decrease in Endo III-sensitive sites by 74%) protective effects were found, while none of the other parameters was altered.

CONCLUSIONS

Our results show that a dose of GTE, which is equivalent to consumption of 500 ml GT/p/day in humans protects lymphocytes and to a lesser extent inner organs against oxidative DNA damage, while no effect was seen with a lower dose corresponding to an uptake of 100 ml/p/day.

Green tea consumption and hematologic malignancies in Japan: the Ohsaki study

Several biologic studies have reported that green tea constituents have antitumor effects on hematologic malignancies. However, the effects in humans are uncertain. The authors used data from the Ohsaki National Health Insurance Cohort Study in Japan to evaluate the association between green tea consumption and the risk of hematologic malignancies. Study participants were 41,761 Japanese adults aged 40-79 years without a history of cancer at baseline who answered a food frequency questionnaire survey in 1994. During 9 years of follow-up beginning in 1995, the authors documented 157 hematologic malignancies, including 119 cases of lymphoid neoplasms and 36 cases of myeloid neoplasms. Hazard ratios were calculated by using the Cox proportional hazards regression model. Risk of hematologic malignancies was inversely associated with green tea consumption. The multivariate-adjusted hazard ratio of hematologic malignancies for 5 cups/day or more compared with less than 1 cup/day of green tea was 0.58 (95% confidence interval: 0.37, 0.89). The corresponding risk estimate was 0.52 (95% confidence interval: 0.31, 0.87) for lymphoid neoplasms and 0.76 (95% confidence interval: 0.32, 1.78) for myeloid neoplasms. This inverse association was consistent across sex and body mass index strata. In conclusion, green tea consumption was associated with a lower risk of hematologic malignancies.

Effects of co-administration of tea epigallocatechin-3-gallate (EGCG) and caffeine on absorption and metabolism of EGCG in humans

Based on the ratios of (-)-epigallocatechin-3-gallate (EGCG) and caffeine (CAF) levels found in commercial tea drinks, EGCG and CAF were co-administered to human volunteers at various EGCG/CAF ratios, and plasma EGCG was determined by high performance liquid chromatography with chemiluminescence detection. As for the results, in plasma taken after ingestion of a beverage containing 95 mg of EGCG alone, the area under the plasma EGCG concentration-time curve (AUC) was 857 ngxh/ml. A higher AUC (1,370 ngxh/ml) was observed when subjects ingested a beverage containing EGCG (95 mg) and a low amount of CAF (40 mg). In the case of ingestion of a beverage containing EGCG (95 mg) and a high amount of CAF (180 mg), the AUC tended to be somewhat higher (1,165 ngxh/ml), but not significantly so, compared with the beverage with EGCG alone. These findings (modulation of plasma EGCG level by CAF) provide ideas for modulating the bioavailability of tea catechins, which can be applied to tea-related drinks and foods.

Microwave-assisted water extraction of green tea polyphenols

INTRODUCTION

Green tea, a popular drink with beneficial health properties, is a rich source of specific flavanols (polyphenols). There is a special interest in the water extraction of green tea polyphenols since the composition of the corresponding extracts is expected to reflect the one of green tea infusions consumed worldwide.

OBJECTIVE

To develop a microwave-assisted water extraction (MWE) of green tea polyphenols.

METHODOLOGY

MWE of green tea polyphenols has been investigated as an alternative to water extraction under conventional heating (CWE). The experimental conditions were selected after consideration of both temperature and extraction time. The efficiency and selectivity of the process were determined in terms of extraction time, total phenolic content, chemical composition (HPLC-MS analysis) and antioxidant activity of the extracts.

RESULTS

By MWE (80 degrees C, 30 min), the flavanol content of the extract reached 97.46 (+/- 0.08) mg of catechin equivalent/g of green tea extract, vs. only 83.06 (+/- 0.08) by CWE (80 degrees C, 45 min). In particular, the concentration of the most bioactive flavanol EGCG was 77.14 (+/- 0.26) mg of catechin equivalent/g of green tea extract obtained by MWE, vs 64.18 (+/- 0.26) mg/g by CWE.

CONCLUSION

MWE appears more efficient than CWE at both 80 and 100 degrees C, particularly for the extraction of flavanols and hydroxycinnamic acids. Although MWE at 100 degrees C typically affords higher yields in total phenols, MWE at 80 degrees C appears more convenient for the extraction of the green tea-specific and chemically sensitive flavanols.

Albumin stabilizes (-)-epigallocatechin gallate in human serum: binding capacity and antioxidant property

(-)-Epigallocatechin gallate (EGCg) is the major component of green tea and is known to show strong biological activity, although it can be easily oxidized under physiological conditions. In this study, we indicate that EGCg is stable in human serum and that human serum albumin (HSA) stabilizes EGCg under aerobic condition. Although EGCg is usually decomposed within 1 h in aqueous solution at neutral pH, EGCg in serum and phosphate buffer (pH 7.4) containing HSA was stable over 1 h, even at neutral and slightly alkaline pH. Under these conditions, EGCg binds to HSA non-covalently. The sulfhydryl group acts as an antioxidant for EGCg oxidation. Incubation of EGCg with HSA is accompanied by the oxidation of a free sulfhydryl group in HSA. These results suggest that the antioxidant property and the binding capacity of HSA contribute to the stabilization of EGCg in human serum.

Effects of epigallocatechin gallate on rotenone-injured murine brain cultures

Green tea polyphenol epigallocatechin-3-gallate (EGCG) is reported to have antioxidant abilities and to counteract beneficially mitochondrial impairment and oxidative stress. The present study was designed to investigate neuroprotective effects of EGCG on rotenone-treated dissociated mesencephalic cultures and organotypic striatal cultures. Rotenone is a potent inhibitor of complex I of the respiratory chain, which in vitro causes pathological and neurochemical characteristics of diseases in which mitochondrial impairment is involved, e.g., Parkinson's disease. Treatment with EGCG (0.1, 1, 10 muM) alone had no significant effects on mesencephalic cultures. In striatal slice cultures, EGCG led to a significant increase of propidium iodide (PI) uptake and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM), but not dihydroethidium (DHE) fluorescence intensity. Rotenone (20 nM on the eighth DIV for 48 h) significantly decreased the numbers and the neurite lengths of TH ir neurons by 23 and 34% in dissociated mesencephalic cell cultures compared to untreated controls. Exposure of striatal slices to rotenone (0.5 mM for 48 h) significantly increased PI uptake, and DAF-FM and DHE fluorescence intensities by 41 and 136 and 19%, respectively, compared to controls. Against rotenone, in dissociated mesencephalic cultures, EGCG produced no significant effect on either the number or neurite lengths of THir neurons compared to rotenone-treated cultures, but EGCG significantly decreased PI uptake by 19% and DAF-FM fluorescence intensity by 19 and 58%, respectively, compared to increase in rotenone-exposed striatal slices. On the other hand, EGCG did not affect superoxide (O(2) (-)) formation as detected with DHE. These data indicate that EGCG slightly protects striatal slices by counteracting nitric oxide (NO(.)) production by rotenone. In conclusion, EGCG partially protects striatal slices but not dissociated cells against rotenone toxicity.

The effects of polyphenols on survival and locomotor activity in Drosophila melanogaster exposed to iron and paraquat

Parkinson's disease (PD) is a common progressive neurodegenerative disorder, for which at present no causal treatment is available. On the understanding that the causes of PD are mainly oxidative stress and mitochondrial dysfunction, antioxidants and other drugs are expected to be used. In the present study, we demonstrated for the first time that pure polyphenols such as gallic acid, ferulic acid, caffeic acid, coumaric acid, propyl gallate, epicatechin, epigallocatechin, and epigallocatechin gallate protect, rescue and, most importantly, restore the impaired movement activity (i.e., climbing capability) induced by paraquat in Drosophila melanogaster, a valid model of PD. We also showed for the first time that high concentrations of iron (e.g. 15 mM FeSO(4)) are able to diminish fly survival and movement to a similar extent as (20 mM) paraquat treatment. Moreover, paraquat and iron synergistically affect both survival and locomotor function. Remarkably, propyl gallate and epigallocatechin gallate protected and maintained movement abilities in flies co-treated with paraquat and iron. Our findings indicate that pure polyphenols might be potent neuroprotective agents for the treatment of PD against stressful stimuli.

Quantitation of chafurosides A and B in tea leaves and isolation of prechafurosides A and B from oolong tea leaves

A procedure was developed for the quantitative determination of chafuroside A, a flavone C-glycoside with potent anti-inflammatory activity, and its regioisomer chafuroside B, as well as isovitexin and vitexin, by selected reaction monitoring liquid chromatography-tandem mass spectrometry (SRM LC-MS/MS) analysis. This method was successfully applied to commercial leaves of green tea, houji tea, oolong tea, and black tea. High levels of chafurosides A and B were found in oolong tea leaves that had been heated at >140 degrees C. Next, their precursors, prechafurosides A and B, were isolated from methanol extract of oolong tea leaves prepared from Shizu 7132, Camellia sinensis (L.) O. Kuntze, by partition with n-butanol and H2O and chromatography on Diaion SP-825, Sephadex LH-20, and ODS C-18, guided by assay of chafuroside formation. Prechafurosides A and B gave chafurosides A and B, respectively, in good yields when heated at 160 degrees C for 0.5 h. Solvolysis of prechafurosides A and B with pyridine and dioxane quantitatively afforded isovitexin and vitexin, respectively. On the basis of these results and physicochemical data (MS, UV, and NMR), prechafurosides A and B were concluded to be new flavone C-glycoside sulfates, isovitexin-2''-sulfate and vitexin-2''-sulfate, respectively.

Separation of catechins and methylxanthines in tea samples by capillary electrochromatography

In this paper, the simultaneous separation of several polyphenols such as (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, theophylline, caffeine in green and black teas by capillary electrochromatography (CEC) was developed. Several experimental parameters such as stationary phase type, mobile phase composition, buffer and pH, inner diameter of the columns, sample injection, were evaluated to obtain the complete separation of the analysed compounds. Baseline resolution of the studied polyphenols was achieved within 30 min by using a capillary column (id 100 microm) packed with bidentate C(18) particles for 24.5 cm and a mobile phase composed of 5 mM ammonium acetate buffer pH 4 with H(2)O/ACN (80:20, v/v). The applied voltage and the temperature were set at 30 kV and 20 degrees C. Precision, detection and quantification limits, linearity, and accuracy were investigated. A good linearity (R(2) > 0.9992) was achieved over a concentration working range of 2-100 microg/mL for all the analytes. LOD and LOQ were 1 and 2 microg/mL, respectively, for all studied compounds. The CEC method was applied to the analysis of those polyphenols in green and black tea samples after an extraction procedure. Good recovery data from accuracy studies ranged between 90% and 112% for all analytes.

Exposure and toxicity of green tea polyphenols in fasted and non-fasted dogs

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.

Catechin induced longevity in C. elegans: from key regulator genes to disposable soma

The flavanol catechin is a ubiquitous metabolite within the plant kingdom. Several health benefits have previously been reported, however, to date, most attention has been devoted to gallated forms of catechin. This study utilized the nematode Caenorhabditis elegans to assess potential life expanding effects of non-gallated catechin. Longevity was observed at three different catechin concentrations, an effect that was neither linked to a specific temperature nor to the viability of the feeding bacteria. Taken all tests into account, hormesis, calorie restriction, as well as the presence of simple antioxidative or antibacterial effects could be excluded. Likewise, the insulin/IGF-1 like signaling pathway and the calmodulin kinase II pathway were not considered to play a major mechanic role. Moreover, stress resistance was enhanced without a marked alteration in reproductive behavior. In addition, lifespan tests with various stress and lifespan relevant mutant strains revealed that the life span extending phenotype was absent in mev-1, daf-2, akt-2 and nhr-8. Finally, catechin elicited a significant reduction in body length, a finding that is in line with the "Disposable Soma Theory". It is proposed that catechin modulates an energy-intensive stress response and repair system that results in reduced body length and an enhanced lifespan.

Difference in growth suppression and apoptosis induction of EGCG and EGC on human promyelocytic leukemia HL-60 cells

Growth suppression and apoptosis inducing effect of (-)-epigallocatechin 3-gallate (EGCG) and (-)-epigallocatechin (EGC) were studied against human promyeolcytic leukemia, HL-60 cells. EGCG showed higher growth suppression against HL-60 cells than EGC. IC(50) values for EGCG were 60.0 microM and EGC was 107.7 microM, respectively. Both EGCG and EGC induced apoptosis evidenced by nuclei fragmentation. Nuclear fragmentation was observed as a time-dependent manner and the extent of nuclear fragmentation was slightly higher in EGCG-treated cells than EGC-treated cells. The expression level of Bcl-2 was decreased and caspase-3 was activated by EGCG or EGC treatment. The extent in decrease of Bcl-2 and activation caspase-3 were more extensively occurred in EGCG-treated cells than in EGC-treated cells. These data corresponded to the growth suppression data. EGC showed no cytotoxicity to a normal V79-4 cell line and EGCG showed slight cytotoxicity at higher concentrations.

Involvement of oxidative pathways in cytokine-induced secretory phospholipase A2-IIA in astrocytes

Recent studies have suggested the involvement of secretory phospholipase A2-IIA (sPLA2-IIA) in neuroinflammatory diseases. Although sPLA2-IIA is transcriptionally induced through the NF-kappaB pathway by pro-inflammatory cytokines, whether this induction pathway is affected by other intracellular signaling pathways has not been investigated in detail. In this study, we demonstrated the induction of sPLA2-IIA mRNA and protein expression in astrocytes by cytokines and detected the protein in the culture medium after stimulation. We further investigated the effects of oxidative pathways and botanical antioxidants on the induction pathway and observed that IL-1beta-induced sPLA2-IIA mRNA expression in astrocytes is dependent on ERK1/2 and PI-3 kinase, but not p38 MAPK. In addition to apocynin, a known NADPH oxidase inhibitor, botanical antioxidants, such as resveratrol and epigallocatechin gallate, also inhibited IL-1beta-induced sPLA2-IIA mRNA expression. These compounds also suppressed IL-1beta-induced ERK1/2 activation and translocation of the NADPH oxidase subunit p67 phox from cytosol to membrane fraction. Taken together, these results support the involvement of reactive oxygen species from NADPH oxidase in cytokine induction of sPLA2-IIA in astrocytes and promote the use of botanical antioxidants as protective agents for inhibition of inflammatory responses in these cells.

Reversible Regulation of Cell Cycle-Related Genes by Epigallocatechin Gallate for Hibernation of Neonatal Human Tarsal Fibroblasts

We investigated the hibernation effect of epigallocatechin-3- O-gallate (EGCG) on neonatal human tarsal fibroblasts (nHTFs) by analyzing the expression of cell cycle-related genes. EGCG application to culture media moderately inhibited the growth of nHTFs, and the removal of EGCG from culture media led to complete recovery of cell growth. EGCG resulted in a slight decrease in the cell population of the S and G2/M phases of cell cycle with concomitant increase in that of the G0/G1 phase, but this cell cycle profile was restored to the initial level after EGCG removal. The expression of cyclin D1 (CCND1), CCNE2, CCN-dependent kinase 6 (CDK6), and CDK2 was restored, whereas that of CCNA, CCNB1, and CDK1 was irreversibly attenuated. The expression of a substantial number of genes analyzed by cDNA microarray was affected by EGCG application, and these affected expression levels were restored to the normal levels after EGCG removal. We also found the incorporation of FITC-EGCG into the cytosol of nHTFs and its further nuclear translocation, which might lead to the regulation of the exogenous signals directed to genes for cellular responses including proliferation and cell cycle progression. These results suggest that EGCG temporarily affects not only genes related to the cell cycle but also various other cellular functions.

Green tea polyphenols mitigate deterioration of bone microarchitecture in middle-aged female rats

Our previous study demonstrated that green tea polyphenols (GTP) benefit bone health in middle-aged female rats without (sham, SH) and with ovariectomy (OVX), because of GTP's antioxidant capacity. The current study further evaluates whether GTP can restore bone micro-structure in both gonad-intact and gonadal-hormone-deficient middle-aged female rats. A 16-week study was performed based on a 2 (SH vs. OVX)x3 (no GTP, 0.1% GTP, and 0.5% GTP in drinking water) factorial design using 14-month-old female rats (n=10/group). An additional 10 rats were euthanized at the beginning of study to provide baseline parameters. Analysis using dual-energy X-ray absorptiometry, histomorphometry, and micro-computed tomography showed that GTP supplementation resulted in (a) increased trabecular volume, thickness, number, and bone formation of proximal tibia, periosteal bone formation rate of tibia shaft, and cortical thickness and area of femur, and (b) decreased trabecular separation and bone erosion of proximal tibia, and endocortical bone eroded surface of tibia shaft. We concluded that drinking water supplemented with GTP mitigated deterioration of bone microarchitecture in both intact and ovariectomized middle-aged female rats by suppressing bone erosion, enhancing bone formation, and modulating endocortical and cancellous bone compartments, resulting in a larger net bone volume.

Catechin-induced activation of the LKB1/AMP-activated protein kinase pathway

Catechins are abundant in green tea and induce a variety of biologic actions, including anti-cancer, anti-obesity, and anti-diabetes effects, and their clinical application has been widely investigated. To clarify the underlying molecular mechanisms of these actions, we examined the effect of catechins on AMP-activated protein kinase (AMPK) in cultured cells and in mice. In Hepa 1-6, L6, and 3T3-L1 cells, epigallocatechin gallate (EGCG) induced increases in AMPKalpha and the downstream target acetyl-CoA carboxylase (ACC) phosphorylation, and AMPKalpha activity. Analysis of the molecular specificity of eight naturally occurring catechins revealed that catechins with a gallocatechin moiety or a galloyl residue act as AMPK activators. In addition, phosphorylation of LKB1, which is a tumor-suppressor protein and a major AMPK-kinase, was increased by catechin treatment. EGCG-induced phosphorylation of LKB1 and AMPKalpha was suppressed by treatment with catalase, suggesting that reactive oxygen species are involved in EGCG-induced activation of the LKB1/AMPK pathway. Oral administration of EGCG (200mg/kg body weight) to BALB/c mice induced an increase in AMPKalpha activity in the liver concomitant with a significant increase in AMPKalpha and ACC phosphorylation. EGCG administration also increased oxygen consumption and fat oxidation, as determined by indirect calorimetry. These findings suggest that multiple effects of catechins, including anti-obesity and anti-cancer effects, are mediated, at least in part, by the activation of LKB1/AMPK in various tissues, and that these effects vary according to the catechin structure.

Green tea catechins for treatment of external genital warts

This review evaluates the antiviral, antioxidant, and immunostimulatory properties of green tea catechins. Two randomized trials evaluating the activity and efficacy of green tea catechins in the management of external genital warts are presented, and the reported side effects associated with this topical treatment modality are outlined. Finally, the mechanism of action, percent of wart clearance, time to clearance, and toxicity profile of green tea catechins are compared with those of podofilox and imiquimod, 2 other patient-administered topical agents approved for treatment of anogenital warts.

Long-term tea intake is associated with reduced prevalence of (type 2) diabetes mellitus among elderly people from Mediterranean islands: MEDIS epidemiological study

PURPOSE

We sought to evaluate the link between long-term tea intake and prevalence of type 2 diabetes mellitus, in a sample of elderly adults.

MATERIALS AND METHODS

During 2005-2007, 300 men and women from Cyprus, 142 from Mitilini, 100 from Samothraki, 114 from Kefalonia, 131 from Crete, 150 from Corfu and 103 from Zakynthos (aged 65 to 100 years) were enrolled. Dietary habits (including tea consumption) were assessed through a food frequency questionnaire. Among various factors, fasting blood glucose was measured and prevalence of (type 2) diabetes mellitus was estimated.

RESULTS

54% of the participants reported that they consume tea at least once a week (mean intake 1.6 +/- 1.1 cup/day). The majority of the participants (98%) reported green or black tea consumption. The participants reported that they consume tea for at least 30 years of their life. After adjusting for various confounders, tea intake was inversely associated with lower blood glucose levels (b +/- SEM per 1 cup: - 5.9 +/- 2.6 mg/dL, p = 0.02). Moreover, multiple logistic regression revealed that moderate tea consumption (1 - 2 cups/day) was associated with 70% (95% CI 41% to 86%) lower odds of having (type 2) diabetes, irrespective of age, sex, body mass, smoking, physical activity status, dietary habits and other clinical characteristics.

CONCLUSION

The presented findings suggest that long-term tea intake is associated with reduced levels of fasting blood glucose and lower prevalence of diabetes, in a cohort of elderly people living in Mediterranean islands.

(-)-Epigallocatechin-3-gallate is a novel Hsp90 inhibitor

(-)-Epigallocatechin-3-gallate (EGCG), a major component of green tea, protects against certain types of cancers, although the mechanism has not yet been determined. It was previously demonstrated that EGCG blocks aryl hydrocarbon receptor (AhR)-mediated transcription induced by the potent carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Unlike other AhR antagonists that directly bind to the AhR, EGCG inhibits AhR-mediated transcription by binding to hsp90. We hypothesize that EGCG exerts anti-AhR and anticancer effects by acting as an hsp90 inhibitor. Using proteolytic footprinting, immunoprecipitation, and an ATP-agarose pull-down assay, EGCG was found to directly modulate the conformation of hsp90 and bind at or near to a C-terminal ATP binding site. Hsp90 chaperone function, as assessed by its ability to mediate refolding of denatured luciferase, was inhibited by EGCG treatment. Hsp90 dimerization, which occurs at the C-terminal end, was also inhibited by EGCG treatment. Coimmunoprecipitation studies showed that EGCG stabilizes an AhR complex that includes hsp90 and XAP2 (hepatitis B virus X-associated protein 2), and decreases the association of aryl hydrocarbon nuclear translocator (Arnt) with ligand-activated AhR. Thus, EGCG, through its ability to bind to hsp90, blocks AhR response element (AhRE) recognition. These studies indicate a novel mechanism whereby EGCG inhibits ligand-induced AhRE binding and AhR-mediated transcriptional activity. In EGCG-treated human ovarian carcinoma SKOV3 cells, decreased levels of several cancer-related hsp90 client proteins, such as ErbB2, Raf-1 and phospho-AKT, were observed. EGCG also modified the association of hsp90 with several cochaperones. Overall, these data indicate that EGCG is a novel hsp90 inhibitor. Further studies are needed to determine if this has a role in the antitumor actions of EGCG.

Effects of (-) epigallocatechin-3-gallate on Na(+) currents in rat dorsal root ganglion neurons

The natural product (-) epigallocatechin-3-gallate (EGCG) is the major polyphenolic constituent found in green tea. Dorsal root ganglion neurons are primary sensory neurons, and express tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents, which are both actively involved in the generation and propagation of nociceptive signals. Effects of EGCG on tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neurons were investigated using the whole-cell variation of the patch-clamp techniques. EGCG inhibited both types of Na(+) currents potently and in a concentration-dependent manner. The apparent dissociation constant, K(d), was estimated to be 0.74 and 0.80 microM for tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents, respectively. (-) Epigallocatechin (EGC) was far less potent to inhibit Na(+) currents than EGCG, suggesting that gallate moiety of EGCG is an important functional group to modulate Na(+) currents. EGCG had little or no effect on the activation or steady-state inactivation voltage of either type of Na(+) current. EGCG simply reduced the availability of Na(+) channels for activation. Thus, EGCG appears to bind to resting Na(+) channels to inhibit them. EGCG slowed the recovery of tetrodotoxin-sensitive Na(+) current from inactivation. The property of EGCG to inhibit sensory Na(+) currents can be utilized to develop an analgesic agent.