(−)-Epigallocatechin-3-gallate (EGCG) inhibits starch digestion and improves glucose homeostasis through direct or indirect activation of PXR/CAR-mediated phase II metabolism in diabetic mice
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As a major component of green tea, (-)-epigallocatechin-3-gallate (EGCG) has attracted interest from scientists owing to its potential to combat a variety of human diseases including abnormal glucose metabolism in obesity and diabetes. This study aims to (1) evaluate the molecular mechanism of EGCG in starch digestion before EGCG absorption; (2) investigate the link between PXR/CAR-mediated phase II metabolism and glucose homeostasis after EGCG is transported to small intestine and liver. EGCG suppressed starch hydrolysis both in vitro and in vivo. Molecular simulation results demonstrated that EGCG could bind to the active site of α-amylase and α-glucosidase, acting as an inhibitor. In addition, the anti-diabetic action of EGCG was investigated in high fat diet and STZ-induced type 2 diabetes. EGCG improved glucose homeostasis and inhibited the process of gluconeogenesis (PEPCK and G-6-Pase) and lipogenesis (SREBP-1C, FAS and ACC1) in the liver. Meanwhile, EGCG treatment activated PXR/CAR, accompanied by upgrading PXR/CAR-mediated phase II drug metabolism enzyme expression in small intestine and liver, involving SULT1A1, UGT1A1 and SULT2B1b. Dietary polyphenol EGCG could serve as a promising PXR/CAR activator and therapeutic intervention in diabetes.Keywords:
Pregnane X receptor
Carbohydrate Metabolism
Digestion
Homeostasis
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Pterostilbene
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Abstract Epigallocatechin‐3‐gallate is a primary bioactive constituent part of green tea that has preservative influence on human health. Due to the small amounts and high expenditure of trading epigallocatechin‐3‐gallate, it is necessary to improve a trade‐operational and influential preliminary method to purify epigallocatechin‐3‐gallate from natural funds. This study suggests that the polyamide column separation is a simple method for large‐scale separation and purification of epigallocatechin‐3‐gallate from green tea for food applications. The most important innovation in this study is that high standard yield and high purity epigallocatechin‐3‐gallate are obtained from polyamide column after catechin mixture is obtained by supercritical fluid extraction. The purity of caffeine is checked with thin‐layer chromatography and high performance thin‐layer chromatography the resulting decaffeinated catechin mixture is isolated on polyamide support column using ethanol: water mixture as eluent. Epigallocatechin‐3‐gallate is isolated from the mixture as pure. The pure epigallocatechin‐3‐gallate is obtained starting with a mixture of 75% ethanol and 25% water elution.
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Epicatechin gallate
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목적: 세계적으로 가장 널리 소비되고 있는 기호식품 중 하나인 녹차는 항당뇨, 항고혈압 및 항암효과가 뛰어난 것으로 알려져 있다. 본 연구는 녹차의 구성성분인 epigallocatechin-3-gallate (EGCG)가 난소암 세포주들에서 세포 성장 억제 효과, 세포주기 변화 및 세포사멸 효과를 확인하고, 세포주기 관련 유전자와 단백질의 발현 변화를 조사하여 항암 효과를 확인하고자 하였다. 연구 방법: 난소암 세포주들에서 EGCG에 의한 항암효과를 확
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Following oral administration of (-)-epigallocatechin gallate to rats, the presence of (-)-epigallocatechin gallate was examined in the portal blood. A compound present in the blood was identified as (-)-epigallocatechin gallate by HPLC and mass spectrometry analysis. The results clearly demonstrate that (-)-epigallocatechin gallate is absorbed, at least in part, into rat portal blood.
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본 연구에서는 free radicals의 산화적인 손상에 의한 세포사멸에 있어서 녹차성분의 하나인 (-)epigallocatechin gallate의 억제효과를 규명하였다. 우선 radicals 소거작용에 있어서 (-)epigallocatechin gallate는 탁월한 항산화력을 발휘하였다. 혈관손상과 직결되는 혈관내피세포를 이용하여 hydroxyl radical의 H₂O₂에 의한 산화적인 손상을 유발시켜 세포생존율을 조사하였는데, (-)epigallocatechin gallate는 100 μM 이하의 농도에서는 그 자체 독성이 없었고 H₂O₂의 산화적 독성효과를 경감시키는 것으로 나타났다. 그러나 flavone인 apigenin은 고농도에서 독성을 가지며 radical 소거활성이 미약하고 H₂O₂의 산화독성은 경감시키지 못하였다. 다양한 세포사멸 검출법을 이용하여 세포 및 세포핵의 형태학적 양상을 조사한 결과, 0.25mM H₂O₂에 의한 24시간 이내의 세포죽음은 세포사멸현상에 의하여 초래되었다. 그러나 이러한 세포사멸과정을 겪고 있는 혈관내피세포에 50 μM (-)epigallocatechin gallate를 처리한 경우에 세포핵의 응축이나 DNA fragmentation은 사라지고 세포사멸작용을 억제시키는 효과를 보여주었다. 예상한 바와 같이 apigenin의 flavone은 세포사멸 억제효과를 나타내지 못하였다. (-)Epigallocatechin gallate는 녹차에 함유된 catechins의 하나로서 free radicals의 산화적 손상에 의한 세포사멸에 있어서 탁월한 방어적인 세포생리학적인 기능을 지니고 있으며, 혈관노화 및 혈관손상과 함께 유발되는 세포사멸성 심혈관 질환의 예방과 치료에 기능성 식품 신소재로서 활용될 수 있으리라 본다.
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(−)-Epigallocatechin-3-gallate (EGCG) was loaded in heat treated β-lactoglobulin (β-Lg) for the preservation of antioxidant activity. The effects of pH (2.5–7.0), the heating temperature of β-Lg (30–85 °C), the molar ratio of β-Lg to EGCG (1:2–1:32), and the β-Lg concentration (1–10 mg/mL) on the properties of β-Lg–EGCG complexes were studied. All four factors significantly influenced the particle size, the ζ-potential, and the entrapment efficiency of EGCG and EGCG loading in β-Lg particles. A stable and clear solution system could be obtained at pH 6.4–7.0. The highest protection of EGCG antioxidant activity was obtained with β-Lg heated at 85 °C and the molar ratio of 1:2 (β-Lg: EGCG). β-Lg–EGCG complexes were found to have the same secondary structure as native β-Lg.
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Epigallocatechin gallate (EGCG) is the catechin with the highest antioxidant activity present in green tea.
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A semi-synthetic route to the D-ring analogs of (–)-epigallocatechin gallate (EGCG) from the relatively abundant (–)-epigallocatechin (EGC), isolated from green tea leaves, is described. A natural product (13), found in Cistus salvifolius, its acetate (14) and analog (17) were synthesized by this method. Their inhibitory activities against proteasomes were investigated.Key words: green tea, (–)-epigallocatechin gallate (EGCG), (–)-epigallocatechin (EGC), proteasome inhibition.
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Green tea extract
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Dihydrotestosterone
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Epicatechin gallate
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