Abstract
Huge epidemiological and clinical studies have confirmed that black tea is a rich source of health-promoting ingredients, such as catechins and theaflavins (TFs). Furthermore, TF derivatives mainly include theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3′-gallate (TF2B), and theaflavin-3,3′-digallate (TF3). All of these TFs exhibit extensive usages in pharmaceutics, foods, and traditional medication systems. Various indepth studies reported that how TFs modulates health effects in cellular and molecular mechanisms. The available literature regarding the pharmacological activities of TFs has revealed that TF3 has remarkable anti-inflammatory, antioxidant, anticancer, antiobesity, antiosteoporotic, and antimicrobial properties, thus posing significant effects on human health. The current manuscript summarizes both the chemistry and various pharmacological effects of TFs on human health, lifestyle or aging associated diseases, and populations of gut microbiota. Furthermore, the biological potential of TFs has also been focused to provide a deeper understanding of its mechanism of action.
Highlights
Tea, is a dried leaf–infused beverage obtained from the leaves of a small shrub originally from China, has become the world’s second popular beverage after water
TFs inhibit the biosynthesis of fatty acids, upregulate their oxidation, and diminish liver and adipose tissue stress by improving glucose tolerance and insulin sensitivity through AMPK/acetyl-coA carboxylase (ACC), IL-6/ STAT3 signaling pathway, and tumor necrosis factor-α (TNF-α), COX-2, phosphoglycerate mutase 1 (PGAM1), acetyl-CoA carboxylase-β (ACAC-β), and enoyl-CoA hydratase 1 (ECHS1) expression in in vivo and in vitro studies [34, 53]
TF1, TF2A, TF2B, and TF3 are the major TF derivatives reported for a wide range of biological activities
Summary
Tea, is a dried leaf–infused beverage obtained from the leaves of a small shrub originally from China, has become the world’s second popular beverage after water. Black tea have 30-40% polyphenols comprising mainly TFs, thearubigins (TRs), and bisflavonols [5]. Theaflavins (TFs) comprised of a large group of polyphenols abundantly present in black and oolong teas. TFs are the main oxidation products of catechins and aggregates during the fermentation steps [5, 6]. The monogallate ester at 3′-position played an important role in posing antioxidant effect of TFs. Compared to TF2A, TF2B potentially inhibits the superoxide radical, H2O2, and hydroxyl radical. The galloyl group present in TFs is mainly responsible for the antioxidant and anticancer activity [11]. TFs exert health beneficial may get effected by regulating various cellular signaling pathways the activation of nuclear factor erythroid-2 related factor-2 (Nrf2)/Keap (Kelch-like ECH associated protein-1) signaling cascade while blocking the mitogen-activated protein kinase (MAPK) signaling to mitigate cellular inflammatory responses [15]. The challenges and research gaps are discussed with future research directions
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