China
Africa
Explore chapters and articles related to this topic
Treatment of skin with antioxidants
Published in Roger L. McMullen, Antioxidants and the Skin, 2018
Who hasn’t heard someone say, “I prefer tea—no coffee for me please.” Whether that person knows it or not, he or she is making a judicious decision to drink the more antioxidant rich beverage. Black, green, and oolong teas come from the same plant, Camellia sinensis, and are rich with various types of polyphenols. The difference between the three teas results from their manufacturing processes and, consequently, their antioxidant compositions are different. For example, green tea undergoes a milder preparation process and is chock-full of catechins, which belong to a class of polyphenols known as the flavanols (Figure 8.14). The four principle catechins in green tea consist of epicatechin, epigallocatechin, epicatechin-3-gallate, and epigallocatechin-3-gallate. Epigallocatechin-3-gallate is the most abundant of the catechins in green tea and, accordingly, the most studied.130 Black tea, like oolong tea, is subjected to an enduring fermentation process that converts the epicatechins to condensed forms of polyphenols, which predominantly contains the theaflavin and thearubigin (Figure 8.15).
(-)-Epigallocatechin gallate from green tea increases the level of a DNA repair enzyme
Published in Elida Zairina, Junaidi Khotib, Chrismawan Ardianto, Syed Azhar Syed Sulaiman, Charles D. Sands, Timothy E. Welty, Unity in Diversity and the Standardisation of Clinical Pharmacy Services, 2017
The development of drugs from natural ingredients to prevent or treat cancer has now reached the molecular level. The ability to prevent cancer risk is closely related to the ability to repair DNA damage. Various pollutants and carcinogenic compounds attack the DNA and produce cancer cells. Cancer can be avoided if this DNA damage is prevented. One strategy of cancer treatment is to search compounds or extracts that are able to protect DNA from damage that causes mutations. Research using green tea major component (-)-epigallocatechin gallate (EGCG) has proved that there is a significant relationship between EGCG levels and DNA repair (Efimova et al., 2016). Increasing the activity of DNA repair enzymes in cells is an important step to prevent DNA damage, thereby preventing tumors and cancer. It has been shown that administration of 45.34% theaflavin or 28.32% EGCG prevents DNA damage induced by 7,12-dimethylbenz(a)anthracene (DMBA). This suggests that EGCG has the ability to protect cells from DNA damage (Srivastava et al. 2013). Therefore, EGCG from green tea has a high potential to be developed into a compound that provides protection against tumors and cancer.
Tea Polyphenolic Compounds against Herpes Simplex Viruses
Published in Satya Prakash Gupta, Cancer-Causing Viruses and Their Inhibitors, 2014
Tin-Chun Chu, Sandra D. Adams, Lee H. Lee
Green tea extract has high concentrations of catechins that have been found to have more antioxidant activity than black tea extract (Cheng 2006). Epicatechins have a high number of hydroxyl (OH) groups that are responsible for antioxidant activity (Luczaj and Skrzydlewska 2005; Zhang and Rock 2004). GTPs have the ability to chelate redox active transition metals, interrupt chain oxidation reactions and accept free radicals, and they also can provide hydrogen atoms (Chen et al. 2003). All of these properties make GTPs the ideal antioxidant. Recent studies have shown that certain extracts, specifically concentrated theaflavin extracts made from black tea, can be just as effective as catechins in terms of antioxidant properties. In fact, theaflavins have been shown to protect cells against oxidative damage, thus confirming its antioxidant capabilities (Luczaj and Skrzydlewska 2005; Yang et al. 2007).
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
As a fully fermented tea, black tea is characterized with red liquor, red leaves, and sweet taste, and the fermentation process is crucial for the formation of its unique flavor and health effect due to the generation of theaflavins, thearubigins, and theabrownins. Theaflavins, the oxidation products of a pair of epimerized catechins, are responsible for the golden color and astringent taste of black tea (Wan, 2003). Furthermore, theaflavins, especially the gallated theaflavins, were found to be positively correlated with the bioactivities of black tea (Qu et al., 2020). In black tea, theaflavins are primarily composed of four monomers: theaflavin (TF), theaflavin-3-gallate (TF3G), theaflavin-3′-gallate (TF3’G), and theaflavin-3, 3′-digallate (TFDG), which vary in the position and number of galloyl moiety. The hydroxyl groups attached to the theaflavin skeleton and galloyl moiety enable theaflavins to effectively scavenge free radicals and promote the various bioactivities of theaflavins (Xie et al., 2018). For instance, theaflavins can suppress the adhesion and invasion of hepatoma cells by scavenging hydroxyl radicals and reactive oxygen species (ROS) (Zhang et al., 2000). Additionally, theaflavins can trigger a reduction of ROS in human colon adenocarcinoma cancer cells due to their excellent radical-scavenging ability (Tan et al., 2019). Furthermore, theaflavins are reported to develop resistance against bacteria, virus, inflammation, hyperglycemia, and cardiovascular disease (Liu et al., 2013). As one of the major naturally functional components in black tea, theaflavins have a promising prospect of clinical application.
The Effect of Different Treatments of (–)-Epigallocatechin-3-Gallate on Colorectal Carcinoma Cell Lines
Published in Nutrition and Cancer, 2018
Yang-Ping Ding, Zi-Li Gao, Bing-Can Chen, Kanyasiri Rakariyatham, Hua-Yi Suo, Hua-Rong Tong, Hang Xiao
In summary, our results showed that O-EGCG had stronger inhibitory effect on HCT116 cells than that of EGCG. Consequently, we can infer that the degraded metabolites of EGCG exerted an important anticancer effect. Furthermore, our previous study indicated that the same pretreated theaflavin-3,3′-digallate, which is one of theaflavins, also possessed higher inhibitory effect on HCT116 cells than theaflavin-3,3′-digallate itself (42). So, we can speculate that all the same pretreated polyphenols might play a greater efficacy on this cell line primarily through their byproducts and intermediates than parent substances due to their instability.
Lycopene alleviates oxidative stress-induced cell injury in human vascular endothelial cells by encouraging the SIRT1/Nrf2/HO-1 pathway
Published in Clinical and Experimental Hypertension, 2023
Wenhai Guo, Danping Huang, Shaodong Li
Recently, Nrf2 has gained much attention and attention in the search for therapeutic agents that attenuate cardiovascular diseases by inhibiting oxidative stress (46). Nrf2, a key neuroprotective transcription factor belonging to the cap’n’collar family that is an essential component of the antioxidant stress pathway (47). Nrf2 could bind to antioxidant response elements and promote the transcription of downstream antioxidant enzymes, mainly including HO-1, SOD, CAT, etc. (48–50). In addition, Nrf2 also could regulate the biosynthesis of GSH and then enhance the body’s antioxidant capacity (51). A large number of basic experimental studies confirmed that enhancement of the Nrf2/HO-1 pathway has a significant protective effect on cardiovascular diseases. A study revealed that theaflavin may exert anti-atherosclerotic effects by strengthening the Nrf2/HO-1 pathway (52). Poria cocos polysaccharides exert their inhibitory effects on oxidative stress to treat AS by enhancing the Nrf2/HO-1 pathway (53). Further, previous studies have discovered that lycopene encourages nuclear ectopy of Nrf2 and activates the Nrf2/HO-1 pathway, which in turn protects hepatocytes from hypoxia/reoxygenation injury (54). Our results similarly showed that lycopene treatment could partially counteract the inhibition of H2O2 stimulation on SIRT1/Nrf2/HO-1 pathway proteins in ECV-304 and HMEC-1 cells. Nrf2 could be activated by multiple regulators and pathways among them SIRT1, a member of the sirtuin family of proteins, which is widely expressed in various tissues and organs, and is able to be involved in a variety of pathological processes (55,56). Multiple studies have confirmed that activation of the SIRT1/Nrf2 signaling pathway can alleviate cardiovascular diseases. Zhang et al. (57) demonstrated that hydrogen sulfide could restore the cardioprotective effects of sevoflurane postconditioning-induced diabetic rats by activating oxidative stress mediated by the SIRT1/Nrf2 signaling pathway. Besides, yang et al. (58) have found that quercetin significantly reduced cerebral infarct volume, neurological deficits, blood–brain barrier permeability, and reactive oxygen species production through the SIRT1/Nrf2/HO-1 pathway. This further confirms the findings of the present study.