Molecules

Editorial

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5 pages, 354 KiB

Open AccessEditorial

Catechin in Human Health and Disease

by Mamoru Isemura

Molecules 2019, 24(3), 528; https://doi.org/10.3390/molecules24030528 - 1 Feb 2019

Cited by 176 | Viewed by 14972

Abstract

Catechin, the name of which is derived from catechu of the extract of Acacia catechu L [...] Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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Research

Jump to: Editorial, Review

10 pages, 1519 KiB

Open AccessArticle

(−)-Epigallocatechin-3-Gallate Decreases Osteoclastogenesis via Modulation of RANKL and Osteoprotegrin

by Shih-Tse Chen, Lin Kang, Chau-Zen Wang, Peng-Ju Huang, Hsuan-Ti Huang, Sung-Yen Lin, Shih-Hsiang Chou, Cheng-Chang Lu, Po-Chih Shen, Yi-Shan Lin and Chung-Hwan Chen

Molecules 2019, 24(1), 156; https://doi.org/10.3390/molecules24010156 - 3 Jan 2019

Cited by 45 | Viewed by 5720

Abstract

Osteoporosis is the second most common epidemiologic disease in the aging population worldwide. Previous studies have found that frequent tea drinkers have higher bone mineral density and less hip fracture. We previously found that (−)-epigallocatechin gallate (EGCG) (20–100 µmol/L) significantly suppressed receptor activator [...] Read more.

Osteoporosis is the second most common epidemiologic disease in the aging population worldwide. Previous studies have found that frequent tea drinkers have higher bone mineral density and less hip fracture. We previously found that (−)-epigallocatechin gallate (EGCG) (20–100 µmol/L) significantly suppressed receptor activator of nuclear factor-kB ligand (RANKL)-induced osteoclastogenesis and pit formation via inhibiting NF-κB transcriptional activity and nuclear transport of NF-κB in RAW 264.7 cells and murine primary bone marrow macrophage cells. The most important regulation in osteoclastogenesis is the receptor activator of nuclear factor-kB/RANKL/osteoprotegrin (RANK/RANKL/OPG) pathway. In this study, we used the coculture of RAW 264.7 cells and the feeder cells, ST2, to evaluate how EGCG regulated the RANK/RANKL/OPG pathway in RAW 264.7 cells and ST2 cells. We found EGCG decreased the RANKL/OPG ratio in both mRNA expression and secretory protein levels and eventually decreased osteoclastogenesis by TRAP (+) stain osteoclasts and TRAP activity at low concentrations—1 and 10 µmol/L—via the RANK/RANKL/OPG pathway. The effective concentration can be easily achieved in daily tea consumption. Taken together, our results implicate that EGCG could be an important nutrient in modulating bone resorption. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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11 pages, 2884 KiB

Open AccessArticle

(−)-Epigallocatechin-3-Gallate (EGCG) Enhances Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

by Sung-Yen Lin, Lin Kang, Chau-Zen Wang, Han Hsiang Huang, Tsung-Lin Cheng, Hsuan-Ti Huang, Mon-Juan Lee, Yi-Shan Lin, Mei-Ling Ho, Gwo-Jaw Wang and Chung-Hwan Chen

Molecules 2018, 23(12), 3221; https://doi.org/10.3390/molecules23123221 - 6 Dec 2018

Cited by 72 | Viewed by 4522

Abstract

Osteoporosis is the second most-prevalent epidemiologic disease in the aging population worldwide. Cross-sectional and retrospective evidence indicates that tea consumption can mitigate bone loss and reduce risk of osteoporotic fractures. Tea polyphenols enhance osteoblastogenesis and suppress osteoclastogenesis in vitro. Previously, we showed that [...] Read more.

Osteoporosis is the second most-prevalent epidemiologic disease in the aging population worldwide. Cross-sectional and retrospective evidence indicates that tea consumption can mitigate bone loss and reduce risk of osteoporotic fractures. Tea polyphenols enhance osteoblastogenesis and suppress osteoclastogenesis in vitro. Previously, we showed that (−)-epigallocatechin-3-gallate (EGCG), one of the green tea polyphenols, increased osteogenic differentiation of murine bone marrow mesenchymal stem cells (BMSCs) by increasing the mRNA expression of osteogenesis-related genes, alkaline phosphatase activity and, eventually, mineralization. We also found that EGCG could mitigate bone loss and improve bone microarchitecture in ovariectomy-induced osteopenic rats, as well as enhancing bone defect healing partially via bone morphogenetic protein 2 (BMP2). The present study investigated the effects of EGCG in human BMSCs. We found that EGCG, at concentrations of both 1 and 10 µmol/L, can increase mRNA expression of BMP2, Runx2, alkaline phosphatase (ALP), osteonectin and osteocalcin 48 h after treatment. EGCG increased ALP activity both 7 and 14 days after treatment. Furthermore, EGCG can also enhance mineralization two weeks after treatment. EGCG without antioxidants also can enhance mineralization. In conclusion, EGCG can increase mRNA expression of BMP2 and subsequent osteogenic-related genes including Runx2, ALP, osteonectin and osteocalcin. EGCG further increased ALP activity and mineralization. Loss of antioxidant activity can still enhance mineralization of human BMSCs (hBMSCs). Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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12 pages, 1054 KiB

Open AccessArticle

Effects of In Vitro Digestion on the Content and Biological Activity of Polyphenols from Acacia mearnsii Bark

by Xiao Chen, Jia Xiong, Lingxiao He, Yu Zhang, Xun Li, Liping Zhang and Fei Wang

Molecules 2018, 23(7), 1804; https://doi.org/10.3390/molecules23071804 - 20 Jul 2018

Cited by 13 | Viewed by 4552

Abstract

The stability and bioaccessibility of polyphenol from Acacia mearnsii bark were measured at various stages during in vitro simulated digestion. Subsequently, the changes in the total polyphenol content (TPC) and biological activity were studied. The results showed that the phenolic compounds from A. [...] Read more.

The stability and bioaccessibility of polyphenol from Acacia mearnsii bark were measured at various stages during in vitro simulated digestion. Subsequently, the changes in the total polyphenol content (TPC) and biological activity were studied. The results showed that the phenolic compounds from A. mearnsii remained stable, and TPC underwent few changes during gastric digestion. Nonetheless, intestinal digestion led to the degradation of proanthocyanidins (PAs) and a significant decrease in TPC (26%). Degradation was determined by normal-phase HPLC and gel permeation chromatography. Only monomers, dimers, and trimers of flavan-3-ols were identified in the serum-accessible fraction for characterization of their bioaccessibility. The results also indicated the obvious antioxidant capacity of PAs from A. mearnsii bark, and ~53% of the α-glucosidase–inhibitory effect was preserved. All these findings show that PAs from A. mearnsii bark as a native plant source may be particularly beneficial for human health as a natural nutritional supplement. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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17 pages, 1328 KiB

Open AccessArticle

Beneficial Effects of Green Tea Catechins on Neurodegenerative Diseases

by Monira Pervin, Keiko Unno, Tomokazu Ohishi, Hiroki Tanabe, Noriyuki Miyoshi and Yoriyuki Nakamura

Molecules 2018, 23(6), 1297; https://doi.org/10.3390/molecules23061297 - 29 May 2018

Cited by 197 | Viewed by 20845

Abstract

Tea is one of the most consumed beverages in the world. Green tea, black tea, and oolong tea are made from the same plant Camellia sinensis (L.) O. Kuntze. Among them, green tea has been the most extensively studied for beneficial effects on [...] Read more.

Tea is one of the most consumed beverages in the world. Green tea, black tea, and oolong tea are made from the same plant Camellia sinensis (L.) O. Kuntze. Among them, green tea has been the most extensively studied for beneficial effects on diseases including cancer, obesity, diabetes, and inflammatory and neurodegenerative diseases. Several human observational and intervention studies have found beneficial effects of tea consumption on neurodegenerative impairment, such as cognitive dysfunction and memory loss. These studies supported the basis of tea’s preventive effects of Parkinson’s disease, but few studies have revealed such effects on Alzheimer’s disease. In contrast, several human studies have not reported these favorable effects with regard to tea. This discrepancy may be due to incomplete adjustment of confounding factors, including the method of quantifying consumption, beverage temperature, cigarette smoking, alcohol consumption, and differences in genetic and environmental factors, such as race, sex, age, and lifestyle. Thus, more rigorous human studies are required to understand the neuroprotective effect of tea. A number of laboratory experiments demonstrated the benefits of green tea and green tea catechins (GTCs), such as epigallocatechin gallate (EGCG), and proposed action mechanisms. The targets of GTCs include the abnormal accumulation of fibrous proteins, such as Aβ and α-synuclein, inflammation, elevated expression of pro-apoptotic proteins, and oxidative stress, which are associated with neuronal cell dysfunction and death in the cerebral cortex. Computational molecular docking analysis revealed how EGCG can prevent the accumulation of fibrous proteins. These findings suggest that GTCs have the potential to be used in the prevention and treatment of neurodegenerative diseases and could be useful for the development of new drugs. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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13 pages, 1450 KiB

Open AccessFeature PaperArticle

Binding of Catechins to Staphylococcal Enterotoxin A

by Yuko Shimamura, Mio Utsumi, Chikako Hirai, Shogo Nakano, Sohei Ito, Ai Tsuji, Takeshi Ishii, Takahiro Hosoya, Toshiyuki Kan, Norio Ohashi and Shuichi Masuda

Molecules 2018, 23(5), 1125; https://doi.org/10.3390/molecules23051125 - 9 May 2018

Cited by 22 | Viewed by 5371

Abstract

Staphylococcal enterotoxin A (SEA) is a toxin protein, and is the most common cause of staphylococcal food poisoning. Polyphenols, such as catechins, are known to interact with proteins. In this study, we investigated the binding of catechins to SEA using SPR (Biacore), Fourier [...] Read more.

Staphylococcal enterotoxin A (SEA) is a toxin protein, and is the most common cause of staphylococcal food poisoning. Polyphenols, such as catechins, are known to interact with proteins. In this study, we investigated the binding of catechins to SEA using SPR (Biacore), Fourier transform infrared spectroscopy (FT-IR), isothermal titration calorimetry (ITC), and protein-ligand docking. We found that (−)-epigallocatechin gallate (EGCG) could strongly bind to SEA. According to thermodynamic parameters, a negative ΔG indicated that the interaction between EGCG and SEA was spontaneous, and the electrostatic force accompanied by hydrophobic binding forces may play a major role in the binding. Data from Western blot analysis and docking simulation suggest that the hydroxyl group at position 3 of the galloyl group in the catechin structure was responsible for binding affinity with the Y91 of the A-6 region of SEA active sites. Our results provide further understanding of the binding interactions between catechins and SEA, and the inhibition of toxin activities by catechins. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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12 pages, 26139 KiB

Open AccessArticle

Epigallocatechin Gallate-Modified Gelatin Sponges Treated by Vacuum Heating as a Novel Scaffold for Bone Tissue Engineering

by Yoshitomo Honda, Yoshihiro Takeda, Peiqi Li, Anqi Huang, Satoshi Sasayama, Eiki Hara, Naoya Uemura, Mamoru Ueda, Masanori Hashimoto, Kenji Arita, Naoyuki Matsumoto, Yoshiya Hashimoto, Shunsuke Baba and Tomonari Tanaka

Molecules 2018, 23(4), 876; https://doi.org/10.3390/molecules23040876 - 11 Apr 2018

Cited by 28 | Viewed by 6333

Abstract

Chemical modification of gelatin using epigallocatechin gallate (EGCG) promotes bone formation in vivo. However, further improvements are required to increase the mechanical strength and bone-forming ability of fabricated EGCG-modified gelatin sponges (EGCG-GS) for practical applications in regenerative therapy. In the present study, we [...] Read more.

Chemical modification of gelatin using epigallocatechin gallate (EGCG) promotes bone formation in vivo. However, further improvements are required to increase the mechanical strength and bone-forming ability of fabricated EGCG-modified gelatin sponges (EGCG-GS) for practical applications in regenerative therapy. In the present study, we investigated whether vacuum heating-induced dehydrothermal cross-linking of EGCG-GS enhances bone formation in critical-sized rat calvarial defects. The bone-forming ability of vacuum-heated EGCG-GS (vhEGCG-GS) and other sponges was evaluated by micro-computed tomography and histological staining. The degradation of sponges was assessed using protein assays, and cell morphology and proliferation were verified by scanning electron microscopy and immunostaining using osteoblastic UMR106 cells in vitro. Four weeks after the implantation of sponges, greater bone formation was detected for vhEGCG-GS than for EGCG-GS or vacuum-heated gelatin sponges (dehydrothermal cross-linked sponges without EGCG). In vitro experiments revealed that the relatively low degradability of vhEGCG-GS supports cell attachment, proliferation, and cell–cell communication on the matrix. These findings suggest that vacuum heating enhanced the bone forming ability of EGCG-GS, possibly via the dehydrothermal cross-linking of EGCG-GS, which provides a scaffold for cells, and by maintaining the pharmacological effect of EGCG. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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13 pages, 2820 KiB

Open AccessArticle

Antioxidant and Cytoprotective Effects of Tibetan Tea and Its Phenolic Components

by Hong Xie, Xican Li, Zhenxing Ren, Weimin Qiu, Jianlan Chen, Qian Jiang, Ban Chen and Dongfeng Chen

Molecules 2018, 23(2), 179; https://doi.org/10.3390/molecules23020179 - 24 Jan 2018

Cited by 51 | Viewed by 6013

Abstract

Tibetan tea (Kangzhuan) is an essential beverage of the Tibetan people. In this study, a lyophilized aqueous extract of Tibetan tea (LATT) was prepared and analyzed by HPLC. The results suggested that there were at least five phenolic components, including gallic [...] Read more.

Tibetan tea (Kangzhuan) is an essential beverage of the Tibetan people. In this study, a lyophilized aqueous extract of Tibetan tea (LATT) was prepared and analyzed by HPLC. The results suggested that there were at least five phenolic components, including gallic acid, and four catechins (i.e., (+)-catechin, (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG), and (−)-epigallocatechin gallate). Gallic acid, the four catechins, and LATT were then comparatively investigated by four antioxidant assays: ferric reducing antioxidant power, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•) scavenging, 1,1-diphenyl-2-picryl-hydrazl radical scavenging, and 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging assays. In these assays, LATT, along with the five phenolic components, increased their antioxidant effects in a concentration-dependent manner; however, the half maximal scavenging concentrations of ECG were always lower than those of CG. Gallic acid and the four catechins were also suggested to chelate Fe²⁺ based on UV-visible spectral analysis. Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC−ESI−Q−TOF−MS/MS) analysis suggested that, when mixed with PTIO•, the five phenolic components could yield two types of radical adduct formation (RAF) products (i.e., tea phenolic dimers and tea phenolic-PTIO• adducts). In a flow cytometry assay, (+)-catechin and LATT was observed to have a cytoprotective effect towards oxidative-stressed bone marrow-derived mesenchymal stem cells. Based on this evidence, we concluded that LATT possesses antioxidative or cytoprotective properties. These effects may mainly be attributed to the presence of phenolic components, including gallic acid and the four catechins. These phenolic components may undergo electron transfer, H⁺-transfer, and Fe²⁺-chelating pathways to exhibit antioxidative or cytoprotective effects. In these effects, two diastereoisomeric CG and ECG showed differences to which a steric effect from the 2-carbon may contribute. Phenolic component decay may cause RAF in the antioxidant process. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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21 pages, 10006 KiB

Open AccessFeature PaperArticle

Liposomal TriCurin, A Synergistic Combination of Curcumin, Epicatechin Gallate and Resveratrol, Repolarizes Tumor-Associated Microglia/Macrophages, and Eliminates Glioblastoma (GBM) and GBM Stem Cells

by Sumit Mukherjee, Juliet N. E. Baidoo, Samay Sampat, Andrew Mancuso, Lovena David, Leah S. Cohen, Shuiqin Zhou and Probal Banerjee

Molecules 2018, 23(1), 201; https://doi.org/10.3390/molecules23010201 - 18 Jan 2018

Cited by 80 | Viewed by 10613

Abstract

Glioblastoma (GBM) is a deadly brain tumor with a current mean survival of 12–15 months. Despite being a potent anti-cancer agent, the turmeric ingredient curcumin (C) has limited anti-tumor efficacy in vivo due to its low bioavailability. We have reported earlier a strategy [...] Read more.

Glioblastoma (GBM) is a deadly brain tumor with a current mean survival of 12–15 months. Despite being a potent anti-cancer agent, the turmeric ingredient curcumin (C) has limited anti-tumor efficacy in vivo due to its low bioavailability. We have reported earlier a strategy involving the use two other polyphenols, epicatechin gallate (E) from green tea and resveratrol (R) from red grapes at a unique, synergistic molar ratio with C (C:E:R: 4:1:12.5, termed TriCurin) to achieve superior potency against HPV+ tumors than C alone at C:E:R (μM): 32:8:100 (termed 32 μM+ TriCurin). We have now prepared liposomal TriCurin (TrLp) and demonstrated that TrLp boosts activated p53 in cultured GL261 mouse GBM cells to trigger apoptosis of GBM and GBM stem cells in vitro. TrLp administration into mice yielded a stable plasma concentration of 210 nM C for 60 min, which, though sub-lethal for cultured GL261 cells, was able to cause repolarization of M2-like tumor (GBM)-associated microglia/macrophages to the tumoricidal M1-like phenotype and intra-GBM recruitment of activated natural killer cells. The intratumor presence of such tumoricidal immune cells was associated with concomitant suppression of tumor-load, and apoptosis of GBM and GBM stem cells. Thus, TrLp is a potential onco-immunotherapeutic agent against GBM tumors. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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2021 KiB

Open AccessArticle

Dietary Copper Reduces the Hepatotoxicity of (−)-Epigallocatechin-3-Gallate in Mice

by Najeeb Ahmed Kaleri, Kang Sun, Le Wang, Jin Li, Wenzheng Zhang, Xuan Chen and Xinghui Li

Molecules 2018, 23(1), 38; https://doi.org/10.3390/molecules23010038 - 23 Dec 2017

Cited by 10 | Viewed by 4335

Abstract

We developed Cu-deficient, -sufficient and -super nutrition mice models by feeding them with diet containing 1.68, 11.72 or 51.69 mg of Cu/kg for 28 days, respectively. Then, the mice were treated to (−)-epigallocatechin-3-gallate (EGCG, 750 mg/kg BW) by oral in order to assess [...] Read more.

We developed Cu-deficient, -sufficient and -super nutrition mice models by feeding them with diet containing 1.68, 11.72 or 51.69 mg of Cu/kg for 28 days, respectively. Then, the mice were treated to (−)-epigallocatechin-3-gallate (EGCG, 750 mg/kg BW) by oral in order to assess the acute toxicity of the drug. Following EGCG treatment, the survival rates were 12.5%, 50% and 100% in the Cu-deficient, -sufficient and Cu-super nutrition groups of mice, respectively. Cu level and ceruloplasmin activity in serum were significantly increased with the increase of dietary Cu. However, the Cu supplementation did not produce any obvious impact on serum superoxide dismutase activity. Furthermore, ceruloplasmin, in vitro, significantly promotes EGCG oxidation accompanied with increasing oxidation products and decreasing levels of reactive oxygen species. These results, therefore, suggest that Cu can relieve EGCG hepatotoxicity, possibly by up-regulating ceruloplasmin activity, which can be used to promote EGCG applications. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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Review

Jump to: Editorial, Research

21 pages, 2646 KiB

Open AccessFeature PaperReview

Antiviral Mechanism of Action of Epigallocatechin-3-O-gallate and Its Fatty Acid Esters

by Kunihiro Kaihatsu, Miyuki Yamabe and Yasuhito Ebara

Molecules 2018, 23(10), 2475; https://doi.org/10.3390/molecules23102475 - 27 Sep 2018

Cited by 102 | Viewed by 9719

Abstract

Epigallocatechin-3-O-gallate (EGCG) is the major catechin component of green tea (Cameria sinensis), and is known to possess antiviral activities against a wide range of DNA viruses and RNA viruses. However, few studies have examined chemical modifications of EGCG in [...] Read more.

Epigallocatechin-3-O-gallate (EGCG) is the major catechin component of green tea (Cameria sinensis), and is known to possess antiviral activities against a wide range of DNA viruses and RNA viruses. However, few studies have examined chemical modifications of EGCG in terms of enhanced antiviral efficacy. This paper discusses which steps of virus infection EGCG interferes with, citing previous reports. EGCG appears most likely to inhibits the early stage of infections, such as attachment, entry, and membrane fusion, by interfering with viral membrane proteins. According to the relationships between structure and antiviral activity of catechin derivatives, the 3-galloyl and 5′-OH group of catechin derivatives appear critical to antiviral activities. Enhancing the binding affinity of EGCG to virus particles would thus be important to increase virucidal activity. We propose a newly developed EGCG-fatty acid derivative in which the fatty acid on the phenolic hydroxyl group would be expected to increase viral and cellular membrane permeability. EGCG-fatty acid monoesters showed improved antiviral activities against different types of viruses, probably due to their increased affinity for virus and cellular membranes. Our study promotes the application of EGCG-fatty acid derivatives for the prevention and treatment of viral infections. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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13 pages, 505 KiB

Open AccessReview

Effects of Tea Catechins on Alzheimer’s Disease: Recent Updates and Perspectives

by Kazuki Ide, Norihiro Matsuoka, Hiroshi Yamada, Daisuke Furushima and Koji Kawakami

Molecules 2018, 23(9), 2357; https://doi.org/10.3390/molecules23092357 - 14 Sep 2018

Cited by 78 | Viewed by 7835

Abstract

Alzheimer’s disease (AD) is one of the most common neurodegenerative disorders worldwide. Its incidence is gradually increasing because of an aging demographic. Therefore, AD prevention and modification is important to improve the health status of older adults. Oxidative stress is a component of [...] Read more.

Alzheimer’s disease (AD) is one of the most common neurodegenerative disorders worldwide. Its incidence is gradually increasing because of an aging demographic. Therefore, AD prevention and modification is important to improve the health status of older adults. Oxidative stress is a component of the pathological mechanisms underlying AD. It is caused by a disruption of the balance between reactive oxygen species and antioxidant molecules. This imbalance also causes neuroinflammation. Catechins, which are bioactive components of tea, have antioxidative and anti-inflammatory effects. Moreover, other potential properties related to AD prevention and modification have been reported in in vitro and in vivo studies. Several clinical studies have also been conducted to date. The current review summarizes recent updates and perspectives of the effects of catechins on AD based on the molecular mechanisms and related clinical studies. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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14 pages, 546 KiB

Open AccessReview

Possible Mechanisms of Green Tea and Its Constituents against Cancer

by Yohei Shirakami and Masahito Shimizu

Molecules 2018, 23(9), 2284; https://doi.org/10.3390/molecules23092284 - 7 Sep 2018

Cited by 100 | Viewed by 11323

Abstract

A number of epidemiological, clinical, and experimental researches have indicated that administration of green tea appears to have anti-cancer activity. According to findings of laboratory cell culture studies, a diverse mechanism has been observed underlying the effects of green tea catechins against cancer. [...] Read more.

A number of epidemiological, clinical, and experimental researches have indicated that administration of green tea appears to have anti-cancer activity. According to findings of laboratory cell culture studies, a diverse mechanism has been observed underlying the effects of green tea catechins against cancer. These mechanisms include anti-oxidant activity, cell cycle regulation, receptor tyrosine kinase pathway inhibition, immune system modulation, and epigenetic modification control. This review discusses the results of these studies to provide more insight into the effects of green tea administration on cancers observed to date in this research field. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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28 pages, 3848 KiB

Open AccessReview

Computational Molecular Docking and X-ray Crystallographic Studies of Catechins in New Drug Design Strategies

by Shogo Nakano, Shin-ichi Megro, Tadashi Hase, Takuji Suzuki, Mamoru Isemura, Yoriyuki Nakamura and Sohei Ito

Molecules 2018, 23(8), 2020; https://doi.org/10.3390/molecules23082020 - 13 Aug 2018

Cited by 32 | Viewed by 8077

Abstract

Epidemiological and laboratory studies have shown that green tea and green tea catechins exert beneficial effects on a variety of diseases, including cancer, metabolic syndrome, infectious diseases, and neurodegenerative diseases. In most cases, (−)-epigallocatechin gallate (EGCG) has been shown to play a central [...] Read more.

Epidemiological and laboratory studies have shown that green tea and green tea catechins exert beneficial effects on a variety of diseases, including cancer, metabolic syndrome, infectious diseases, and neurodegenerative diseases. In most cases, (−)-epigallocatechin gallate (EGCG) has been shown to play a central role in these effects by green tea. Catechins from other plant sources have also shown health benefits. Many studies have revealed that the binding of EGCG and other catechins to proteins is involved in its action mechanism. Computational docking analysis (CMDA) and X-ray crystallographic analysis (XCA) have provided detailed information on catechin-protein interactions. Several of these studies have revealed that the galloyl moiety anchors it to the cleft of proteins through interactions with its hydroxyl groups, explaining the higher activity of galloylated catechins such as EGCG and epicatechin gallate than non-galloylated catechins. In this paper, we review the results of CMDA and XCA of EGCG and other plant catechins to understand catechin-protein interactions with the expectation of developing new drugs with health-promoting properties. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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8 pages, 205 KiB

Open AccessFeature PaperReview

Effect of Tea Catechins on Influenza Infection and the Common Cold with a Focus on Epidemiological/Clinical Studies

by Daisuke Furushima, Kazuki Ide and Hiroshi Yamada

Molecules 2018, 23(7), 1795; https://doi.org/10.3390/molecules23071795 - 20 Jul 2018

Cited by 54 | Viewed by 16831

Abstract

Influenza and the common cold are acute infectious diseases of the respiratory tract. Influenza is a severe disease that is highly infectious and can progress to life-threating diseases such as pneumonia or encephalitis when aggravated. Due to the fact that influenza infections and [...] Read more.

Influenza and the common cold are acute infectious diseases of the respiratory tract. Influenza is a severe disease that is highly infectious and can progress to life-threating diseases such as pneumonia or encephalitis when aggravated. Due to the fact that influenza infections and common colds spread easily via droplets and contact, public prevention measures, such as hand washing and facial masks, are recommended for influenza prophylaxis. Experimental studies have reported that tea catechins inhibited influenza viral adsorption and suppressed replication and neuraminidase activity. They were also effective against some cold viruses. In addition, tea catechins enhance immunity against viral infection. Although the antiviral activity of tea catechins has been demonstrated, the clinical evidence to support their utility remains inconclusive. Since the late 1990s, several epidemiological studies have suggested that the regular consumption of green tea decreases influenza infection rates and some cold symptoms, and that gargling with tea catechin may protect against the development of influenza infection. This review briefly summarizes the effect of tea catechins on influenza infection and the common cold with a focus on epidemiological/clinical studies, and clarifies the need for further studies to confirm their clinical efficacy. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

24 pages, 1996 KiB

Open AccessFeature PaperReview

In Vitro and In Silico Studies of the Molecular Interactions of Epigallocatechin-3-O-gallate (EGCG) with Proteins That Explain the Health Benefits of Green Tea

by Koichi Saeki, Sumio Hayakawa, Shogo Nakano, Sohei Ito, Yumiko Oishi, Yasuo Suzuki and Mamoru Isemura

Molecules 2018, 23(6), 1295; https://doi.org/10.3390/molecules23061295 - 28 May 2018

Cited by 60 | Viewed by 9698

Abstract

Green tea has been shown to have beneficial effects on many diseases such as cancer, obesity, inflammatory diseases, and neurodegenerative disorders. The major green tea component, epigallocatechin-3-O-gallate (EGCG), has been demonstrated to contribute to these effects through its anti-oxidative and pro-oxidative [...] Read more.

Green tea has been shown to have beneficial effects on many diseases such as cancer, obesity, inflammatory diseases, and neurodegenerative disorders. The major green tea component, epigallocatechin-3-O-gallate (EGCG), has been demonstrated to contribute to these effects through its anti-oxidative and pro-oxidative properties. Furthermore, several lines of evidence have indicated that the binding affinity of EGCG to specific proteins may explain its mechanism of action. This review article aims to reveal how EGCG-protein interactions can explain the mechanism by which green tea/EGCG can exhibit health beneficial effects. We conducted a literature search, using mainly the PubMed database. The results showed that several methods such as dot assays, affinity gel chromatography, surface plasmon resonance, computational docking analyses, and X-ray crystallography have been used for this purpose. These studies have provided evidence to show how EGCG can fit or occupy the position in or near functional sites and induce a conformational change, including a quaternary conformational change in some cases. Active site blocking, steric hindrance by binding of EGCG near an active site or induced conformational change appeared to cause inhibition of enzymatic activity and other biological activities of proteins, which are related to EGCG’s biological oligomer and formation of their toxic aggregates, leading to the prevention of neurodegenerative diseases and amyloidosis. In conclusion, these studies have provided useful information on the action of green tea/catechins and would lead to future studies that will provide further evidence for rational EGCG therapy and use EGCG as a lead compound for drug design. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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16 pages, 318 KiB

Open AccessReview

A Review on the Weight-Loss Effects of Oxidized Tea Polyphenols

by Dylan O’Neill Rothenberg, Caibi Zhou and Lingyun Zhang

Molecules 2018, 23(5), 1176; https://doi.org/10.3390/molecules23051176 - 14 May 2018

Cited by 72 | Viewed by 21279

Abstract

The mechanistic systems in the body through which tea causes weight loss are complex and multi-dimensional. Additionally, the bioactive components in tea such as catechins, caffeine, and products of tea polyphenol oxidation vary greatly from one major tea type to the next. Green [...] Read more.

The mechanistic systems in the body through which tea causes weight loss are complex and multi-dimensional. Additionally, the bioactive components in tea such as catechins, caffeine, and products of tea polyphenol oxidation vary greatly from one major tea type to the next. Green tea has been the primary subject of consideration for investigation into the preventative health effects of tea because it contains the highest levels of phenolic compounds and retains the highest antioxidant capabilities of any major tea type. However, recent research suggests decreasing body fat accumulation has little to do with antioxidant activity and more to do with enzyme inhibition, and gut microbiota interactions. This paper reviews several different tea polyphenol-induced weight-loss mechanisms, and purposes a way in which these mechanisms may be interrelated. Our original ‘short-chain fatty acid (SCFA) hypothesis’ suggests that the weight-loss efficacy of a given tea is determined by a combination of carbohydrate digestive enzyme inhibition and subsequent reactions of undigested carbohydrates with gut microbiota. These reactions among residual carbohydrates, tea polyphenols, and gut microbiota within the colon produce short-chain fatty acids, which enhance lipid metabolism through AMP-activated protein kinase (AMPK) activation. Some evidence suggests the mechanisms involved in SCFA generation may be triggered more strongly by teas that have undergone fermentation (black, oolong, and dark) than by non-fermented (green) teas. We discussed the mechanistic differences among fermented and non-fermented teas in terms of enzyme inhibition, interactions with gut microbiota, SCFA generation, and lipid metabolism. The inconsistent results and possible causes behind them are also discussed. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

11 pages, 4568 KiB

Open AccessReview

The Role of Catechins in Cellular Responses to Oxidative Stress

by Jurga Bernatoniene and Dalia Marija Kopustinskiene

Molecules 2018, 23(4), 965; https://doi.org/10.3390/molecules23040965 - 20 Apr 2018

Cited by 433 | Viewed by 24303

Abstract

Catechins are polyphenolic compounds—flavanols of the flavonoid family found in a variety of plants. Green tea, wine and cocoa-based products are the main dietary sources of these flavanols. Catechins have potent antioxidant properties, although in some cases they may act in the cell [...] Read more.

Catechins are polyphenolic compounds—flavanols of the flavonoid family found in a variety of plants. Green tea, wine and cocoa-based products are the main dietary sources of these flavanols. Catechins have potent antioxidant properties, although in some cases they may act in the cell as pro-oxidants. Catechins are reactive oxygen species (ROS) scavengers and metal ion chelators, whereas their indirect antioxidant activities comprise induction of antioxidant enzymes, inhibition of pro-oxidant enzymes, and production of the phase II detoxification enzymes and antioxidant enzymes. Oxidative stress and ROS are implicated in aging and related dysfunctions, such as neurodegenerative disease, cancer, cardiovascular diseases, and diabetes. Due to their antioxidant properties, catechins may be beneficial in preventing and protecting against diseases caused by oxidative stress. This article reviews the biochemical properties of catechins, their antioxidant activity, and the mechanisms of action involved in the prevention of oxidative stress-caused diseases. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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18 pages, 3439 KiB

Open AccessFeature PaperReview

Synthesis of Theaflavins and Their Functions

by Masumi Takemoto and Hiroaki Takemoto

Molecules 2018, 23(4), 918; https://doi.org/10.3390/molecules23040918 - 16 Apr 2018

Cited by 95 | Viewed by 9921

Abstract

Numerous epidemiological and interventional clinical studies have consistently reported that black tea is good for human health. The polyphenolic compound, theaflavin, and its galloyl esters (theaflavins) are the primary red pigments in black tea that possess several health benefits, including fat-reducing and glucose-lowering [...] Read more.

Numerous epidemiological and interventional clinical studies have consistently reported that black tea is good for human health. The polyphenolic compound, theaflavin, and its galloyl esters (theaflavins) are the primary red pigments in black tea that possess several health benefits, including fat-reducing and glucose-lowering capabilities and lifestyle-related disease prevention related to anti-obesity, anticancer, anti-atherosclerotic, anti-inflammatory, antiviral, antibacterial, anti-osteoporotic, and anti-dental caries properties. These compounds are produced by key enzymes, such as polyphenol oxidase and peroxidase, from parent green tea catechins present in fresh green tea leaves during the production of black tea leaves or the fermentation of green tea. However, theaflavins are only present in low concentrations in black tea; thus, their extraction from black tea leaves at sufficient levels for use in medical studies has been difficult. To circumvent this issue, different procedures for the synthesis of theaflavins using chemical oxidizing reagents or enzymes have been studied; however, low yields have limited their utility. Recently, however, several biosynthetic methods have been developed for the mass production of theaflavins. Using these methods, the physiological functions of theaflavins in lifestyle-related diseases in mice and humans have also been studied. In this review, we present the synthesis of theaflavins and their health benefits. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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17 pages, 726 KiB

Open AccessReview

Food-Grade Encapsulation Systems for (−)-Epigallocatechin Gallate

by Meng Shi, Yun-Long Shi, Xu-Min Li, Rui Yang, Zhuo-Yu Cai, Qing-Sheng Li, Shi-Cheng Ma, Jian-Hui Ye, Jian-Liang Lu, Yue-Rong Liang and Xin-Qiang Zheng

Molecules 2018, 23(2), 445; https://doi.org/10.3390/molecules23020445 - 17 Feb 2018

Cited by 42 | Viewed by 6166

Abstract

(−)-Epigallocatechin gallate (EGCG) has attracted significant research interest due to its health-promoting effects such as antioxidation, anti-inflammation and anti-cancer activities. However, its instability and poor bioavailability have largely limited its efficacy and application. Food-grade materials such as proteins, carbohydrates and lipids show biodegradability, [...] Read more.

(−)-Epigallocatechin gallate (EGCG) has attracted significant research interest due to its health-promoting effects such as antioxidation, anti-inflammation and anti-cancer activities. However, its instability and poor bioavailability have largely limited its efficacy and application. Food-grade materials such as proteins, carbohydrates and lipids show biodegradability, biocompatibility and biofunctionality properties. Food-grade encapsulation systems are usually used to improve the bioavailability of EGCG. In the present paper, we provide an overview of materials and techniques used in encapsulating EGCG, in which the adsorption mechanisms of food-grade systems during in vitro digestion are reviewed. Moreover, the potential challenges and future work using food-grade encapsulates for delivering EGCG are also discussed. Full article

(This article belongs to the Special Issue Catechin in Human Health and Disease)

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