Preparation of Jellyfish Mucin.

A mucin-type glycoprotein extracted from various species of jellyfish (JF) is named qniumucin (Q-mucin). Compared with general mucins, most of which are from mammals including humans, Q-mucin can be collected on a relatively large scale with high yield. Owing to its simple structure with low heterogeneity, Q-mucin has a potential to be developed into material mucins which opens various applications valuable to humans. On the basis of our present knowledge, here, we describe our protocol for the extraction of Q-mucin, which can be extracted from any JF species worldwide. Experimental protocols to identify the structure of Q-mucin are also introduced.

Effects of an environmental endocrine disruptor, para-nonylphenol on the cell growth of Euglena gracilis: association with the cellular oxidative stress.

Effects of an environmental endocrine disruptor, para-nonylphenol (NP) on the cell growth of a photosynthetic eukaryotic microorganism, Euglena gracilis were analysed under different cell culture conditions. Although NP did not show significant inhibitory effects on the cell growth of E. gracilis (Z and SM strains) under light culture condition, NP exhibited significant suppressive effects under dark culture condition. Exogenous supplementation with lipophilic antioxidants (α-tocopherol, ß-carotene or 6-O-palmitoyl-ascorbic acid) to E. gracilis caused strong preventive effects against NP-induced cell growth inhibition under dark culture condition, but hydrophilic antioxidants [ascorbic acid, glutathione and epigallocatechin gallate (EGCG)] did not show significant preventive effects. NP caused significant generation of reactive oxygen species (ROS) in E. gracilis under dark culture condition, but E. gracilis under light culture condition did not show significant increase in ROS generation. Supplementation with lipophilic antioxidants to E. gracilis caused significant suppressive effects against NP-induced cellular ROS generation under dark culture condition, but hydrophilic antioxidants did not show significant suppressive effects. Furthermore, the productivities of typical cellular antioxidants (α-tocopherol, ß-carotene and ascorbic acid) in E. gracilis under light culture conditions were much higher than those under dark culture conditions.

Oenothein B in Eucalyptus Leaf Extract Suppresses Fructose Absorption in Caco-2 Cells.

Inhibition of fructose absorption may suppress adiposity and adiposity-related diseases caused by fructose ingestion. Eucalyptus leaf extract (ELE) inhibits intestinal fructose absorption (but not glucose absorption); however, its active compound has not yet been identified. Therefore, we evaluated the inhibitory activity of ELE obtained from Eucalyptus globulus using an intestinal fructose permeation assay with the human intestinal epithelial cell line Caco-2. The luminal sides of a cell monolayer model cultured on membrane filters were exposed to fructose with or without the ELE. Cellular fructose permeation was evaluated by measuring the fructose concentration in the medium on the basolateral side. ELE inhibited 65% of fructose absorption at a final concentration of 1 mg/mL. Oenothein B isolated from the ELE strongly inhibited fructose absorption; the inhibition rate was 63% at a final concentration of 5 µg/mL. Oenothein B did not affect glucose absorption. In contrast, the other major constituents (i.e., gallic acid and ellagic acid) showed little fructose-inhibitory activity. To our knowledge, this is the first report that oenothein B in ELE strongly inhibits fructose absorption in vitro. ELE containing oenothein B can prevent and ameliorate obesity and other diseases caused by dietary fructose consumption.

Inhibitory effects of eucalyptus and banaba leaf extracts on nonalcoholic steatohepatitis induced by a high-fructose/high-glucose diet in rats.

Nonalcoholic steatohepatitis (NASH) is a liver disease associated with metabolic syndrome. The aim of this work was to examine whether eucalyptus (Eucalyptus globulus) leaf extract (ELE) and banaba (Lagerstroemia speciosa L.) leaf extract (BLE) inhibited NASH induced by excessive ingestion of fructose in rats. Wistar rats were divided into four groups according to four distinct diets: starch diet (ST), high-fructose/high-glucose diet (FG), FG diet supplemented with ELE, or FG diet supplemented with BLE. All rats were killed after 5 weeks of treatment. Serum alanine aminotransferase and total cholesterol levels were significantly lower in the BLE group than in the FG group. Liver histopathology, including steatosis, lipogranulomas, and perisinusoidal fibrosis, was significantly attenuated in the ELE and BLE groups compared with the FG group. Levels of 2-thiobarbituric acid reactive substances (TBARS), which reflect oxidative injury to the liver, were significantly suppressed by ELE and BLE. Western blotting analysis indicated that interleukin-6 expression levels were significantly lower in the ELE and BLE groups than in the FG group. These results suggest that ELE and BLE reduced lipogenesis, oxidative stress, and inflammatory cytokine expression and thus inhibited NASH induced by excessive ingestion of fructose in rats.

Current pharmacological therapies for nonalcoholic fatty liver disease/nonalcoholic steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) is considered to be a hepatic manifestation of metabolic syndrome, and its incidence is rapidly increasing worldwide. It is currently the most common chronic liver disease. NASH can progress to liver cirrhosis and hepatocellular carcinoma, and may result in liver-related death. Currently, the principal treatment for NAFLD/NASH is lifestyle modification by diet and exercise. However, pharmacological therapy is indispensable because obese patients with NAFLD often have difficulty maintaining improved lifestyles. The pathogenesis of NAFLD/NASH has not been completely elucidated. However, insulin resistance, inflammatory cytokines, and oxidative stress are thought to be important in the development and/or progression of the disease. Currently, insulin sensitizers (thiazolidinediones) and antioxidants (vitamin E) seem to be the most promising therapeutic agents for NAFLD/NASH, and lipid-lowering drugs, pentoxifylline, angiotensin receptor blockers, and n-3 polyunsaturated fatty acids also have promise. However, there is a lack of consensus regarding the most effective and appropriate pharmacotherapy for NAFLD/NASH. Animal experiments suggest that herbal medicines and natural products may be promising therapeutic agents for NAFLD/NASH, but their efficacy and safety are yet to be investigated in human studies. In this paper, we review the existing and potential pharmacological therapies for NAFLD/NASH.

Resveratrol inhibits hypoxia-inducible factor-1α-mediated androgen receptor signaling and represses tumor progression in castration-resistant prostate cancer.

Androgen-dependent prostate cancer inevitably progresses to incurable castration-resistant prostate cancer (CRPC) after androgen deprivation therapy. Because castration-induced hypoxia-inducible factor (HIF)-1α enhances the transcriptional activity of androgen receptor (AR) at low androgen levels mimicking the castration-resistant stage, HIF-1α is expected to be a promising target for suppression of growth of CRPC. We investigated the effect of resveratrol (3,4',5-trihydroxy-trans-stilbene) on the growth of human prostate cancer LNCaP xenografts in castrated male BALB/cSlc-nu/nu mice (5 wk old). The mice were administered a control diet or a resveratrol diet (4 g/kg diet) for 40 d. The resveratrol diet significantly suppressed tumor growth compared to the control diet. In LNCaP xenografts, dietary resveratrol decreased the protein level of HIF-1α, but not the AR coactivator ß-catenin, and reduced the mRNA levels of androgen-responsive genes. In the control group, ß-catenin was predominantly localized in the nucleus with HIF-1α in LNCaP xenografts, whereas dietary resveratrol inhibited the nuclear accumulation of ß-catenin. In hypoxic LNCaP cells at a low androgen level mimicking the castration-resistant stage, hypoxia-induced nuclear accumulation of ß-catenin was inhibited by resveratrol. Furthermore, resveratrol repressed the expression level of HIF-1α even in the presence of a proteasome inhibitor and suppressed hypoxia-enhanced AR transactivation. These results indicate that dietary resveratrol represses nuclear localization of ß-catenin by decreasing the HIF-1α expression, perhaps in a proteasome-independent manner, and inhibits ß-catenin-mediated AR signaling; this contributes to suppression of tumor growth of CRPC.

S-equol enantioselectively activates cAMP-protein kinase A signaling and reduces alloxan-induced cell death in INS-1 pancreatic ß-cells.

S-Equol is enantioselectively produced from the isoflavone daidzein by gut microflora and is absorbed by the body. An increase of pancreatic ß-cell death is directly associated with defects in insulin secretion and an increased risk of type 2 diabetes mellitus. In the present study, we demonstrate that only the S-enantiomer has suppressive effects against alloxan-induced oxidative stress in INS-1 pancreatic ß-cells. S-Equol reduced alloxan-induced cell death in a dose-dependent manner, whereas R-equol had no effects. In contrast, no significant differences were observed between the enantiomers in estrogenic activity. The cytoprotective effects of S-equol were stronger than those of its precursor daidzein and were blocked by the protein synthesis inhibitor cycloheximide. The cytoprotection was diminished when cells were incubated with a protein kinase A (PKA) inhibitor (H89), but not an estrogen receptor inhibitor. S-Equol increased intracellular cAMP levels in an enantioselective manner. S-Equol, but not R-equol, induced phosphorylation of cAMP-response element-binding protein at Ser 133, and induced cAMP-response element-mediated transcription, both of which were diminished in the presence of H89. Taken together, these results show that S-equol enantioselectively increases the survival of INS-1 cells presumably through activating PKA signaling. Thus, S-equol might have applications as an anti-type 2 diabetic agent.

Resveratrol reduces the hypoxia-induced resistance to doxorubicin in breast cancer cells.

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is known to enhance the cytotoxicity of the anticancer drug doxorubicin. On the other hand, breast cancer MCF-7 cells acquire resistance to doxorubicin under hypoxic conditions. In this study, we investigated the effect of resveratrol on hypoxia-induced resistance to doxorubicin in MCF-7 cells. Resveratrol and its derivative 3,5-dihydroxy-4'-methoxy-trans-stilbene, but not 3,5-dimethoxy-4'-hydroxy-trans-stilbene, cancelled hypoxia-induced resistance to doxorubicin at a concentration of 10 µM. Carbonyl reductase 1 (CBR1) catalyzes the conversion of doxorubicin to its metabolite doxorubicinol, which is much less effective than doxorubicin. Hypoxia increased the expression of CBR1 at both mRNA and protein levels, and knockdown of CBR1 inhibited hypoxia-induced resistance to doxorubicin in MCF-7 cells. Knockdown of hypoxia-inducible factor (HIF)-1α repressed the hypoxia-induced expression of CBR1. Resveratrol repressed the expression of HIF-1α protein, but not HIF-1α mRNA, and decreased hypoxia-activated HIF-1 activity. Resveratrol repressed the hypoxia-induced expression of CBR1 at both mRNA and protein levels. Likewise, 3,5-dihydroxy-4'-methoxy-trans-stilbene decreased the hypoxia-induced expression of CBR1 protein, but not 3,5-dimethoxy-4'-hydroxy-trans-stilbene. Furthermore, resveratrol decreased the expression of HIF-1α protein even in the presence of the proteasome inhibitor MG132 in hypoxia. Theses results indicate that in MCF-7 cells, HIF-1α-increased CBR1 expression plays an important role in hypoxia-induced resistance to doxorubicin and that resveratrol and 3,5-dihydroxy-4'-methoxy-trans-stilbene decrease CBR1 expression by decreasing HIF-1α protein expression, perhaps through a proteasome-independent pathway, and consequently repress hypoxia-induced resistance to doxorubicin.

Identification of carbonyl reductase 1 as a resveratrol-binding protein by affinity chromatography using 4'-amino-3,5-dihydroxy-trans-stilbene.

The mechanisms by which resveratrol (3,4',5-trihydroxy-trans-stilbene) elicits diverse health benefits remain unclear because the intracellular target molecules of resveratrol are poorly defined. We screened resveratrol-binding proteins from lysates of MCF-7 breast cancer cells using resveratrol-affinity resin, which was constructed by immobilizing 4'-amino-3,5-dihydroxy-trans-stilbene on activated CH-Sepharose. On SDS-PAGE, two bands were detected as proteins that specifically bound to the resveratrol-affinity resin. One of these, a 30-kDa protein, was identified as human carbonyl reductase 1 (CBR1) by hybrid linear ion trap/time-of-flight mass spectrometry. Similarly, recombinant CBR1 bound to the resveratrol-affinity resin in the absence of resveratrol, but not in the presence of resveratrol. Among its activities, CBR1 catalyzes a NADPH-dependent reduction of the anticancer drug doxorubicin to the cardiotoxin doxorubicinol. The effects of doxorubicin on viability of MCF-7 cells were enhanced by resveratrol, 3,5-dihydroxy-4'-methoxy-trans-stilbene, 3,4'-dihydroxy-5-methoxy-trans-stilbene, and 4'-amino-3,5-dihydroxy-trans-stilbene at concentrations of 1 and 10 µM. Resveratrol and these derivatives inhibited CBR1 activities to a similar degree at concentrations of 100 and 200 µM. However, 3,5-dimethoxy-4'-hydroxy-trans-stilbene and m-hydroquinone had no influence on doxorubicin cytotoxicity or CBR1 activity. Resveratrol inhibited CBR1 activity through an apparent mix of competitive (Ki=55.8 µM) and noncompetitive (αKi=164 µM; α=2.98) inhibition kinetics. These results indicate that (i) resveratrol enhances the cytotoxic effects of doxorubicin on MCF-7 cells; (ii) the moiety that contains the 3,5-dihydroxyl groups of resveratrol, but not the m-hydroquinone structure alone, is required to bind CBR1; and (iii) resveratrol acts as a mixed-type inhibitor of CBR1 activity on doxorubicin.

A yeast bioassay for androgenic and anti-androgenic compounds based on the NH2- and COOH-terminal interaction of androgen receptor.

Androgenic compounds induce an interaction between the NH(2)- and COOH-terminal regions (N-C interaction) of androgen receptor (AR). We describe a rapid yeast bioassay for androgenic and anti-androgenic compounds based on androgen-dependent ß-catenin-enhanced N-C interaction. The bioassay was also effective at detecting compounds that inhibit the N-C interaction in ways that do not involve binding to the ligand-binding domain.

Cobalamin deficiency results in an abnormal increase in L-methylmalonyl-co-enzyme-A mutase expression in rat liver and COS-7 cells.

The aim of the present study was to examine the effects of cobalamin (Cbl) on the activity and expression of L-methylmalonyl-CoA mutase (MCM) in rat liver and cultured COS-7 cells. The MCM holoenzyme activity was less than 5% of the total (holoenzyme+apoenzyme) activity in the liver although rats were fed a diet containing sufficient Cbl. When weanling rats were maintained on a Cbl-deficient diet, the holo-MCM activity became almost undetectable at the age of 10 weeks. In contrast, a marked increase in the total-MCM activity occurred under the Cbl-deficient conditions, and at the age of 20 weeks it was about 3-fold higher in the deficient rats than in the controls (108 (SD 14.5) v. 35 (SD 8.5) nmol/mg protein per min (n 5); P<0.05). Western blot analysis confirmed that the MCM protein level increased significantly in the Cbl-deficient rats. However, the MCM mRNA level, determined by real-time PCR, was rather decreased. When COS-7 cells were cultured in a medium in which 10% fetal bovine serum was the sole source of Cbl, holo-MCM activity was barely detected. The supplementation of Cbl resulted in a large increase in the holo-MCM activity in the cells, but the activity did not exceed 30% of the total-MCM activity even in the presence of Cbl at 10 micromol/l. In contrast, the total-MCM activity was significantly decreased by the Cbl supplementation, indicating that Cbl deficiency results in an increase in the MCM protein level in COS-7 cells as well as in rat liver.

Antidiabetic effect of long-term supplementation with Siraitia grosvenori on the spontaneously diabetic Goto-Kakizaki rat.

Siraitia grosvenori Swingle (SG) is a traditional Chinese fruit used as a folk medicine. Its extract (SG-ex) contains potent sweet elements with a sweetness several hundred times higher than table sugar. We investigated the antidiabetic effect of SG-ex in the type 2 diabetic Goto-Kakizaki (GK) rat. Diabetic 7-week-old GK rats were fed a diet supplemented with 0.4 % of the SG-ex for 13 weeks, and its antidiabetic effects were evaluated. SG-ex had no effect on food intake or body weight. In oral glucose tolerance tests (OGTT), SG-ex supplementation improved the insulin response at 15 min (control, 63 (sem 6) pm; SG-ex, 107 (sem 20) pm; P < 0.05) and reduced the plasma glucose level at 120 min after the glucose administration (control, 18.5 (sem 0.8) mm; SG-ex, 14.8 (sem 0.7) mm; P < 0.05). The total amount of insulin in whole pancreas taken from fasting rats was higher in the SG-ex-supplemented group, which may explain the greater capacity to secrete insulin during the OGTT. Thiobarbituric acid-reactive substances in both the liver and the plasma were lower in the SG-ex-supplemented group, suggesting that an absorbable component in SG-ex has an antioxidative effect on lipid peroxidation, thereby counteracting the oxidative stress caused by a diabetic state. Excreted urine volume and urinary albumin level for 24 h were both reduced in the SG-ex-supplemented group, suggesting the attenuation of kidney damage that is caused by diabetes. These data indicate that SG-ex supplementation may prevent complications and attenuate pathological conditions for type 2 diabetes, along with its sweet characteristics.

Purification and characterization of a corrinoid-compound in an edible cyanobacterium Aphanizomenon flos-aquae as a nutritional supplementary food.

The vitamin B12 concentration of the dried cells of Aphanizomenon flos-aquae was determined by both microbiological method with Lactobacillus delbrueckeii ATCC7830 and chemiluminescence method with intrinsic factor. The Aphanizomenon cells contained 616.3 +/- 30.3 micro g (n = 4) of vitamin B12 per 100 g of the dried cells by the microbiological method. The values determined with the chemiluminescence method, however, were only about 5.3% of the values determined by the microbiological method. A corrinoid-compound was purified from the dried cells and characterized. The purified corrinoid-compound was identified as pseudovitamin B12 (an inactive corrinoid-compound for humans) by silica gel 60 TLC, C18 reversed-phase HPLC, ultraviolet-visible spectroscopy, and 1H NMR spectroscopy. The results suggest that the Aphanizomenon cells are not suitable for use as a vitamin B12 source, especially in vegans.

Abnormal increase in the expression level of proliferating cell nuclear antigen (PCNA) in the liver and hepatic injury in rats with dietary cobalamin deficiency.

Dietary cobalamin (Cbl; vitamin B12) deficiency resulted in severe growth retardation in rats, and body weight in the Cbl-deficient rats at 20 wk of age was significantly lower compared with the age-matched Cbl-sufficient control rats. In contrast, liver weight, when normalized to body weight, was greater in the Cbl-deficient rats than in the controls (p<0.05). The expression level of proliferating cell nuclear antigen (PCNA), a marker for cell proliferation, in the liver was significantly enhanced in the deficient rats, suggesting that cell proliferation is abnormally activated in the liver under Cbl-deficient conditions. In addition, plasma alanine aminotransferase (ALT) activity, a marker for hepatic injury, was also significantly elevated in the deficient rats. When L-carnitine, which is used clinically for the treatment of Cbl-deficient patients with methylmalonic aciduria, was administered to the Cbl-deficient rats by intraperitoneal injection twice per day for 2 wk (each 0.5 mmol), the amount of methylmalonic acid excreted into the urine was significantly reduced, and the plasma ALT activity was lowered to a normal level. However, the PCNA expression in the liver was barely influenced by the treatment with carnitine. In contrast, when the deficient rats were fed an L-methionine-supplemented diet (4 g of L-methionine per kg of the diet) for 2 wk, the increased expression of PCNA was normalized.

Eucalyptus leaf extract inhibits intestinal fructose absorption, and suppresses adiposity due to dietary sucrose in rats.

Sucrose is more lipogenic than starch, and the extreme ingestion of sucrose induces adiposity and obesity. The aim of this study was to examine the effect of the eucalyptus (Eucalyptus globulus) leaf extract (ELE) on adiposity due to dietary sucrose in rats. In addition, in this study, the effect of ELE on intestinal fructose absorption was also examined. Rats were fed a high-sucrose diet (75 % in calorie base) with or without ELE (10 g/kg diet) for 5 weeks. Body weight was lower in the rats receiving ELE than in the controls (342 (sd 37.9) v. 392 (sd 26.0) g (n 7); P<0.05). Furthermore, ELE resulted in decreases in the triacylglycerol concentrations in the plasma (1.44 (sd 0.448) v. 2.79 (sd 0.677) mmol/l (n 7); P<0.05) and liver (19.1 (sd 5.07) v. 44.1 (sd 16.28) micromol/g (n 7); P<0.05). In contrast, ELE did not show any significant effects in the rats fed a starch diet. When rats were orally given ELE 10 min before fructose administration, the intestinal fructose absorption, which was examined by measuring the elevated concentration of fructose in the portal vein at 30 min after the fructose administration, was significantly inhibited in a dose-dependent manner. Furthermore, in rats fed a high-fructose diet, the plasma and hepatic triacylglycerol concentrations were significantly decreased by ELE. These results indicate that ELE, which inhibits the intestinal fructose absorption, can suppress adiposity in rats that ingest large amounts of sucrose or fructose.

Triterpene glycosides of Siraitia grosvenori inhibit rat intestinal maltase and suppress the rise in blood glucose level after a single oral administration of maltose in rats.

The effect of the crude extract from Siraitia grosvenori Swingle (SG-ex) on the postprandial rise in blood glucose level was investigated. The increase in plasma glucose level in response to the oral administration of maltose was significantly suppressed in rats when SG-ex was given orally 3 min before the maltose administration. There was, however, no effect when glucose was administered instead, suggesting that the antihyperglycemic effect of SG-ex is elicited by inhibition of maltase in the small intestinal epithelium. In vitro, SG-ex inhibited rat small intestinal maltase. Similar effects were also observed both in vivo and in vitro when the concentrate of the sweet elements (triterpene glycosides) prepared from SG-ex was used. Furthermore, the main sweet element of SG-ex, mogroside V, and some minor elements such as mogroside IV, siamenoside I, and mogroside III also exhibited maltase inhibitory effect with IC50 values of 14, 12, 10, and 1.6 mM, respectively. These results suggest that SG-ex exerts anti-hyperglycemic effects in rats by inhibiting maltase activity and that these effects are at least partially exerted by its sweet elements, triterpene glycosides.

Effect of carotenoids and ascorbic acid of Japanese persimmons on cellular lipid peroxidation in HepG2 cells.

In this experiment, we examine the functional property of carotenoids; beta-cryptoxanthin (Cry), zeaxanthin (Zea), beta-carotene (Car)) and ascorbic acid (AsA). The accumulation amounts of Cry, Zea and Car in HepG2 cells cultured in the high concentration medium were larger than that in a low concentration. Further those accumulation amounts in long incubation time within 24 hours were greater than that in a shorter time. When the added carotenoid concentration, with or without hydrogen peroxide, increased from 0 to 5 microM in the culture medium, the thiobarbituric acid reaction substance (TBARS) values in the HepG2 cells decreased significantly (p < 0.05). The decrease of TBARS values shows the antioxidative property of the carotenoids. When AsA and Tocopherol(Toc) were added to the medium from 0 to 20 microM, the TBARS values, with or without hydrogen peroxide, decreased significantly with increasing concentrations of AsA and Toc respectively (p < 0.05). The decreased amount of TBARS in 5 microM Cry compared with control(0 microM) was the largest among 6 antioxidants (Cry, Car, Zea, Retinol(Ret), AsA, Toc) used in this experiment.

Pyruvate:NADP+ oxidoreductase is stabilized by its cofactor, thiamin pyrophosphate, in mitochondria of Euglena gracilis.

Pyruvate:NADP(+) oxidoreductase (PNO) is a thiamin pyrophosphate (TPP)-dependent enzyme that plays a central role in the respiratory metabolism of Euglena gracilis, which requires thiamin for growth. When thiamin was depleted in Euglena cells, PNO protein level was greatly reduced, but its mRNA level was barely changed. In addition, a large part of PNO occurred as an apoenzyme lacking TPP in the deficient cells. The PNO protein level increased rapidly, without changes in the mRNA level, after supplementation of thiamin into its deficient cells. In the deficient cells, in contrast to the sufficient ones, a steep decrease in the PNO protein level was induced when the cells were incubated with cycloheximide. Immunofluorescence microscopy indicated that most of the PNO localized in the mitochondria in either the sufficient or the deficient cells. These findings suggest that PNO is readily degraded when TPP is not provided in mitochondria, and consequently the PNO protein level is greatly reduced by thiamin deficiency in E. gracilis.

Effect of tea catechins on cellular lipid peroxidation and cytotoxicity in HepG2 cells.

Tea catechins inhibited TBARS accumulation in HepG2 cells, the order of effectiveness being (-)-epigallocatechin gallate (EGCG) > (-)-epigallocatechin (EGC) > or = (-)-epicatechin gallate (ECG) > (-)-epicatechin (EC). EGCG and EGC protected the depletion of alpha-tocopherol in the cells, and the glutathione content was enhanced by all four catechins. Moreover, all four catechins suppressed the formation of glutathione disulfide and the activation of glutathione peroxidase induced by tert-butylated hydroperoxide.