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Antioxidant properties and application information
Published in Roger L. McMullen, Antioxidants and the Skin, 2018
Epicatechin gallate belongs to a class of flavonoids known as flavanols. Structurally, it is similar to epicatechin, but has the additional gallate functionality. Often, epicatechin gallate and similar compounds are also referred to as catechins. They are found in green tea (Camellia sinensis), cocoa, wine, and other fruits and vegetables. The catechins also consist of (−)-epicatechin, (−)-epigallocatechin, and (−)-epigallocatechin gallate, which are also tabulated in this chapter. In addition to their antioxidant activity, research also suggests that they have anticarcinogenic properties.
Phytonutrients
Published in Parimelazhagan Thangaraj, Medicinal Plants, 2018
Ranganathan Kumar, Sulaxana Kumari Chauhan, Subramanian Vijayalakshmi, Shanmugam Nadanasabapathi
Catechins and Gallic Acids. The major sources of catechins are grapes, berries, cocoa and green tea. Tea contains considerable quantity of gallic acid esters, like epicatechin, epicatechin gallate and epigallocatechin gallate. Numerous studies have suggested that the protective benefits provided by these components were due to their free radical scavenging ability (Hanasaki et al. 1994), their inhibition of eicosanoid synthesis (Moroney et al. 1988) and platelet aggregation (Pace-Asciak et al. 1995). On the basis of experimental evidence in cell culture systems, animal models, as well as epidemiological evidence, Gupta et al. (1999) support the possible use of tea, especially green tea, for prevention of prostate cancer. However, Hollman et al. (1999) regard the question of flavonol protection against cardiovascular disease and cancer as remaining open. In wines, catechins and procyanidins are involved in the astringency sensation (Haslam and Lilley 1988). Catechin is one of the prime phenolics present in grapes and red wines, and is considered to be responsible for the protective effect of red wine against atherosclerotic cardiovascular disease. Donovan et al. (1999) measured catechin and catechin metabolites in the plasma of human subjects following consumption of both alcoholised and dealcoholised red wine. Sulfate and sulfate± glucuronide conjugates, but little free catechin, were present. The metabolites/conjugates of catechin were eliminated from blood with a half-time of approximately 4 h. These data confirmed that the grape polyphenolic flavonoid catechin is well absorbed, but rapidly metabolized and conjugated. The results suggest that the physiological properties of the metabolites in blood and tissues may be more important than the parent compounds found in plants.
Protecting Pancreatic β-cells from Metabolic Insults
Published in Christophe Wiart, Medicinal Plants in Asia for Metabolic Syndrome, 2017
Metabolic syndrome is associated with chronic exposure of β-cells to high concentration of glucose inducing to the production of reactive oxygen species, the activation of nuclear factor-κB, pancreatic and duodenal homeobox-1 inhibition and subsequent reduction of insulin secretion.42 Liquid extracts of tea made by soaking 20 g in 100 ml of boiling water given intragastrically at a dose of 2 ml/100 g body weight/day for 3 weeks to Sprague–Dawley rats poisoned with streptozotocin reduced glycemia by about 40% after 1 week of treatment.43 The extracts given prophylactically for 2 weeks prevented hyperglycemia induced by streptozotocin.43 The plant contains theophylline which has the ability to inhibit cyclic nucleotide phosphodiesterase increasing thus the cytosolic contents of β-cells in cyclic adenosine monophosphate and subsequent activation of protein kinase A and cyclic adenosine monophosphate-regulated guanine nucleotide exchange factor II leading to altered ion channel activity, elevation of cytoplasmic calcium contents and exocytosis of insulin-containing vesicles.44,45 Protein kinase A-mediated phosphorylation of the SUR1 subunit induces the closing of KATP channel closure via ADP-dependent mechanism.46 Caffeine present in this plant has been shown at a single oral dose of 5 mg/kg to increase insulin secretion in healthy volunteers during oral glucose tolerance test as evidenced by a 60% in insulin area under the curve.47 Besides, the oral administration of (−)-epicatechin, (−)-epigallocatechin gallate and (−)-epicatechin gallate from Camellia sinensis (L.) Kuntze are known to inhibit the absorption of carbohydrates and improve the antioxidant capacity of rodents.48 This set of experimental evidence reinforce the notion that the intake of Camellia sinensis (L.) Kuntze infusions could be beneficial in the management of metabolic syndrome. It must be recalled here that green tea infusions are better than concentrated extracts sold for weight loss which have incurred acute liver failure.49
Role of Plant-Derived Flavonoids in Cancer Treatment
Published in Nutrition and Cancer, 2023
Prabha Tiwari, Kaushala Prasad Mishra
Green tea contains large amount of flavanols and galloylated catechins such as epigallocatechin-3-gallate (EGCG), gallocatechin (GC), epigallocatechin (EGC), epicatechin-3-gallate, and epicatechin (EC). Among them, EGCG is a promising candidate for cancer prevention and treatment (109). EGCG can induce apoptosis in various cancer types such as colon, kidney, breast, brain and leukemia (110). In addition to pro-apoptotic, anti-apoptotic and cell cycle regulatory proteins, EGCG can also modulate Ras/ERK/MAPK and PI3K/Akt pathways in various cancer types (111). EGCG can inhibit angiogenesis and metastasis through suppression of MMP-9, VEGF, bFGF, HIF-1α and HIF-1β (112). EGCG can also inhibit transcription factor Nrf2 to inhibit cancer growth and metastasis in colon cancer (113). Moreover, EGCG can produce ROS by its auto-oxidation to induce cell death in pancreatic carcinoma cells, leukemia, hepatocarcinoma, and endometrial adenocarcinoma cells (114). EGCG can also inhibit glucose metabolism in cancer cells to induce anticancer effects (115). Furthermore, self-assembled metal-phenolic nanocomplexes comprised of EGCG efficiently inhibited migration of melanoma cells (116). Moreover, an EGCG nanoemulsion enhanced anticancer effects of EGCG in lung cancer cells through the activation of AMP-activated protein kinase signaling pathway (110).
Medicinal plants in mitigating electromagnetic radiation-induced neuronal damage: a concise review
Published in Electromagnetic Biology and Medicine, 2022
Shamprasad Varija Raghu, Avinash Kundadka Kudva, Golgodu Krishnamurthy Rajanikant, Manjeshwar Shrinath Baliga
Green tea is a popular beverage, and the Tea plant (Camellia sinensis; Figure 1) is one of the most studied plants. According to historical evidence, the tea plant originated in China, Burma, Thailand, Laos, and Vietnam, but it is now cultivated in Sri Lanka, India, and Japan (Jigisha et al. 2012; Katiyar and Raman 2011). The active compounds of green tea are the catechins, epicatechin, epigallocatechin, epicatechin-3-gallate,epigallocatechin-3-gallate, and gallic acids (Chacko et al. 2010; Cooper et al. 2005). Green tea has been reported to be useful as a stimulant, a diuretic, an astringent, a wound-healing agent, to improve digestion, to improve cognitive functions, to treat neurodegenerative disorders, to prevent cancers, and to improve heart function (Chacko et al. 2010; Cooper et al. 2005). It also has anti-inflammatory, antibacterial, antiviral, antimutagenic, and anti-aging properties (Chacko et al. 2010; Cooper et al. 2005).
Study on mechanism of low bioavailability of black tea theaflavins by using Caco-2 cell monolayer
Published in Drug Delivery, 2021
Fengfeng Qu, Zeyi Ai, Shuyuan Liu, Haojie Zhang, Yuqiong Chen, Yaomin Wang, Dejiang Ni
To further investigate the reasons for the poor bioavailability of theaflavins in Caco-2 cells, the effects of P-gp, MRP1, MRP2, MRP3 and BCRP on the transport of theaflavins were explored in this study. And we found that P-gp, MRP1, MRP2, MRP3 and BCRP are associated with the reduced absorption of the four theaflavin monomers, with P-gp playing the most important part, followed by MRPs and BCRP. Studies have shown a stronger effect of P-gp, MRP2 and BCRP on pumping epicatechin than epicatechin gallate (Kadowaki et al., 2008; Ai et al., 2019). Epicatechin is not only a substrate of P-gp, but can also bind and activate its allosteric sites, thus enhancing the efflux activity of P-gp (Wang et al., 2002). Galloyl groups are considered as the major limiting factors to the secretory transport of gallated catechins (Kadowaki et al., 2008). In the present study, P-gp and MRPs exhibited the strongest secretory effect on TF, but the weakest effect on TFDG, possibly due to the inhibition of galloyl groups on the activity of efflux transporters. Interestingly, TF3’G was shown as the only substrate of BCRP. Studies have shown that Ko143 (a derivative of FTC) and anthocyanins bring about conformational changes of BCRP dimers, resulting in an increase of substrate influx by BCRP (Özvegy-Laczka et al., 2005; Dreiseitel et al., 2009). Hence, we speculated that the increase of the influx of theaflavins caused by FTC might be correlated to the conformational alterations of BCRP.