• Journal of Food Hygiene and Safety
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• v.11 no.2
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• pp.77-82
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• 1996

Green tea catechins(GTC) were studied for its inhibitory effect on human platelet aggregation in vitro, for its antithrombotic effect in mice in viro, and bleeding and clotting time in rats. The catechins were isolated and purified from green tea, which were composed of (-)-epigallocatechin gallate, (-)-epigallocatechin, (-)epicatechin gallate and (-)-epicatechin, GTC produced a potent inhibition of human platelet aggregation in a dose-dependent manner against the stimulants such as ADP, collagen, epinephrine and ristocetin n vitro. GTC also prevented death due to the formation of pulmonary thrombosis by platelet aggregates in mice in a dose-de-pendent manner in viro. GTC increased the bleeding time, whole blood clotting time and plasma clotting time in rats, too. These results suggest that GTC is a promising antithrombotic agent.

• Korean Journal of Veterinary Service
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• v.26 no.4
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• pp.339-343
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• 2003

We studied the effect of epigallocatechin-3-gallate(EGCG) on the adipose conversion of 3T3-L1 cells by insulin. In the 10 days of culture with insulin, the fat cells exhibited the increased and larger intracytoplasmic lipid droplets. In contrast, the levels of triglyceride(TG), a marker of adipose conversion, were decreased. However, the levels of glucose were decreased in the adipose conversion. In addition, levels of cholesterol were decreased in the differentiated 3T3-L1 cells.

• YAKHAK HOEJI
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• v.45 no.1
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• pp.101-107
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• 2001

Green tea catechins (GTC) and its major component, (-)-epigallocatechin gallate (EGCG) were studied for their protective effects against reactive oxygen species (ROS)-induced oxidative stress. GTC and EGCG skewed the strong antioxidative effects on the lipid peroxidation of ethyl linolate with Fenton's reagent and free radical scavenging effect to DPPH radical generation. They also protected $H_2O$$_2$- or KO$_2$-induced cytotoxicity in CHL cells or mouse splenocytes. These results indicate that GTC and EGCG are capable of protecting the lipid peroxidation, flee radical generation and cytotoxicity induced by ROS. The mechanism of inhibition in ROS-induced cytotoxicity may be due to their antiofidative and free radical scavenging properties. Therefore, GTC and EGCG may be useful chemopreventive agents by protecting the free radical generation which are involved in cancer and aging.

• Archives of Pharmacal Research
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• v.24 no.4
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• pp.292-296
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• 2001

Three prolyl endopeptidase (PEP) inhibitors were isolated from the methanolic extract of green tea leaves. They were identified as (-)-epigallocatechin gallate, (-)-epicatechin gallate, and (+)-gallucatechin gallate with the $IC_{50}$ values of 1.42${\times}$$10^{-4}$mM, $1.02{\times}10^{-2}$mM, and $1.09{\times}10^{-4}$mM, respectively. They were non-competitive with a substrate in Dixon plots and did not show any significant effects against other serine proteases such as elastase, trypsin, and chymotrypsin, suggesting that they were relatively specific inhibitors against PER The isolated compounds are expected to be useful for preventing and curing of Alzheimer's disease.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.212.2-212.2
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• 2003

In the course of searching for BACE1 (${\beta}$-secretase) inhibitors from natural products, the ethyl acetate soluble fraction of green tea, which was suspected to be rich in catechin content, showed potent inhibitory activity. (-)-Epigallocatechin gallate, (-)-epicatechin gallate, and (-)-gallocatechin gallate ware isolated with IC$\_$50/ values of 1.6${\times}$10$\^$-6/ M, 4.5${\times}$10$\^$-6/ M, and 1.8${\times}$10$\^$-6/ M, respectively. Seven additional authentic catechins were tested for a fundamental structure-activity relationship. (-)-Catechin gallate, (-)-gallocatechin, and (-)-epigallocatechin significantly inhibited BACE1 activity with IC$\_$50/ values of 6.0${\times}$10$\^$-6/ M, 2.5${\times}$10$\^$-6/ M, and 2.4${\times}$10$\^$-6/ M, respectively. (omitted)

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.122.2-123
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• 2000

• Archives of Pharmacal Research
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• v.26 no.7
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• pp.559-563
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• 2003

Cytokines produced by immune cells infiltrating pancreatic islets have been incriminated as important mediators of $\beta$-cell destruction in insulin-dependent diabetes mellitus. In non insulin-dependent diabetes, cytokines are also associated with impaired $\beta$-cell function in high glucose condition. By the screening of various natural products blocking $\beta$-cell destruction, we have recently found that epigallocatechin gallate (EGCG) can prevent the in vitro destruction of RINm5F cell, an insulinoma cell line, that is induced by cytokines. In that study we suggested that EGCG could prevent cytokine-induced $\beta$-cell destruction by down-regulation of nitric oxide synthase (NOS) through inhibition of NF-kB activation. Here, to verify the in vivo antidiabetogenic effect of EGCG, we examined the possibility that EGCG could also prevent the experimental autoimmune diabetes induced by the treatment of multiple low doses of streptozotocin (MLD-STZ), which is recognized as an inducer of type I autoimmune diabetes. Administration of EGCG (100 mg/day/kg for 10 days) during the MLD-STZ induction of diabetes reduced the increase of blood glucose levels caused by MLD-STZ. Ex vivo analysis of $\beta$-islets showed that EGCG downregulates the MLD-STZ-induced expression of inducible NOS (iNOS). In addition, morphological examination showed that EGCG treatment ameliorated the decrease of islet mass induced by MLD-STZ. In combination these results suggest that EGCG could prevent the onset of MLD-STZ-induced diabetes by protecting pancreatic islets. Our results therefore revealed the possible therapeutic value of EGCG for the prevention of diabetes mellitus progression.

• Journal of Life Science
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• v.18 no.2
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• pp.273-278
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• 2008

Various biological resources from plants, animals, mushrooms, microorganisms, and foods were tested for the inhibitory activity against squalene synthase (SQS). Among 32 samples, more than one fourths (9 samples) exhibited significant SQS inhibitory activity. Interestingly, SQS inhibitory activity was detected in the samples such as green tea, fermented soybean paste, and plum juice. The SQS inhibitory activity of green tea was not only high but also stable. Its SQS inhibitors were supposed to be catechin derivatives, which have been known to be main bioactive components in green tea. The galloyl catechins showed higher SQS inhibitory activity compared to the nongalloyl catechins. Especially, (-)-epigallocatechin gallate appeared to be strongest inhibitor against squalene synthase ($IC_{50}=90{\mu}M$).

• Journal of Pharmaceutical Investigation
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• v.37 no.2
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• pp.107-111
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• 2007

Epigallocatechin gallate (EGCC), a flavonoid, is the main component of green tea extracts. EGCG has been reported to be an inhibitor of P-glycoprotein (P-gp) and cytochrom P450 3A(CYP3A4). This study investigated the effect of long-term administration of EGCG on the pharmacokinetics of verapamil in rats. Pharmacokinetic parameters of verapamil were determined after oral administration of verapamil (9 mg/kg) in rats pretreated with EGCG (7.5 mg/hg) for 3 and 9 days. Compared to oral control group, the presence of EGCG significantly (p<0.01) increased the area under the plasma concentration-time curve (AUC) of verapamil by 102% (coad), 83.2% (3 days) and 52.3% (9 days), and the peak concentration $(C_{max})$ by 134% (coad), 120% (3 days) and 66.1% (9 days). The absolute bioavailability (A.B.%) of verapamil was significantly (p<0.01) higher by 8.4% (coad), 7.7% (3 days), 6.4% (9 days) compared to control (4.2%), and presence of EGCG was no significant change in the terminal half-life $(t_{1/2})$ and the time to reach the peak concentration $(T_{max})$ of verapamil. Our results indicate that EGCG significantly enhanced oral bioavailability of verapamil in rats, implying that presence of EGCG could be effective to inhibit the CYP3A4-mediated metabolism and P-gp efflux of verapamil in the intestine. Drug interactions should be considered in the clinical setting when verapamil is coadministrated with EGCG or EGCG-containing dietary.

• Food Science and Biotechnology
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• v.18 no.4
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• pp.971-977
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• 2009

The most abundant tea catechin, epigallocatechin-3-gallate (EGCG), has been reported to inhibit cell proliferation and induce apoptosis in many types of cancer cells. In the present study, effects of EGCG on the growth of oral epithelial cells including CAL-27 oral squamous carcinoma cells and dysplastic oral keratinocytes (DOK) were investigated. EGCG inhibited growth of CAL-27 cells and DOK with $IC_{50}$ of 14.4-21.0 and 5.8-14.2 ${\mu}M$ after 24 and 48 hr incubation, respectively. EGCG was significantly less effective in inhibiting DOK growth. The effects of EGCG, however, were dramatically less pronounced in the presence of superoxide dismutase (SOD) and catalase. Inhibitory effects of EGCG on CAL-27 cell growth were also much less pronounced in the presence of fetal bovine serum (FBS). EGCG induced caspase-3 activation in both CAL-27 and DOK cells in a serum free condition without SOD/catalase; in the presence of 10% FBS and SOD/catalase, EGCG, even at 100 ${\mu}M$, did not affect cell growth. The present results indicate that EGCG inhibited oral cell growth with higher potency to more malignant CAL-27 cells than DOK, and the effects were markedly altered by SOD/catalase and serum content in media.