Green tea extract: Chemistry, antioxidant properties and food applications – A review
TL;DR: Green tea is one of the most popular and extensively used dietary supplement in the United States as discussed by the authors, which contains several polyphenolic components with antioxidant properties, but the predominant active components are the flavanol monomers known as catechins.
About: This article is published in Journal of Functional Foods.The article was published on 2013-10-01. It has received 351 citations till now. The article focuses on the topics: Green tea extract & Lipid oxidation.
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TL;DR: A review of phenolic and polyphenolic compounds can be found in this article, which summarizes both the synthetic and natural phenolic antioxidants, emphasizing their mode of action, health effects, degradation products and toxicology.
1,800 citations
TL;DR: This Review focuses on the diverse constituents of green tea polyphenols and their molecular mechanisms from the perspective of their potential therapeutic function and recent advances on their bioavailability, bioaccessibility, and microbiota.
Abstract: Tea, leaf, or bud from the plant Camellia sinensis, make up some of the beverages popularly consumed in different parts of the world as green tea, oolong tea, or black tea. More particularly, as a nonfermented tea, green tea has gained more renown because of the significant health benefits assigned to its rich content in polyphenols. As a main constituent, green tea polyphenols were documented for their antioxidant, anti-inflammation, anticancer, anticardiovascular, antimicrobial, antihyperglycemic, and antiobesity properties. Recent reports demonstrate that green tea may exert a positive effect on the reduction of medical chronic conditions such as cardiovascular disease, cancer, Alzheimer's disease, Parkinson's disease, and diabetes. The health benefits of green teas, in particular EGCG, are widely investigated, and these effects are known to be primarily associated with the structure and compositions of its polyphenols. This Review focuses on the diverse constituents of green tea polyphenols and their molecular mechanisms from the perspective of their potential therapeutic function. Recent advances of green tea polyphenols on their bioavailability, bioaccessibility, and microbiota were also summarized in this article. Dietary supplementation with green tea represents an attractive alternative toward promoting human health.
293 citations
TL;DR: The application of tea polyphenols in human and animal health is examined, providing a scientific basis for this application in addition to proposing future directions for the development of this resource.
281 citations
Cites background from "Green tea extract: Chemistry, antio..."
...As such, the catechins have strong hydrogen supply capacity on the B and C rings, and the 2,3- double bond and the unsaturated 4-oxo group in the C-ring promote the electron delocalization (free electron) of the ortho-dihydroxy catechol in the Bring (Senanayake, 2013)....
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TL;DR: Polysaccharides and polyphenols were synergistic in reduction of serum leptin levels and in anti-inflammatory activity, suggesting that the polysaccharide combination with polyphenol might be a potential therapy against obesity.
Abstract: Beneficial effects of green tea (Camellia sinensis, Theaceae) extracts against obesity have been reported; however, the anti-obesity ability of the major components of green tea, polysaccharides, polyphenols and caffeine is not clear. Therefore, experiments with total green tea extracts, polyphenols, polysaccharides, caffeine, and a complex of polysaccharide and polyphenol at a dose of 400 or 800 mg kg⁻¹ were conducted on high-fat diet fed rats for 6 weeks to investigate their anti-obesity effects. The results indicated that polyphenols and polysaccharides were responsible for the suppressive effect of green tea extracts on body weight increase and fat accumulation. Moreover, polyphenols, polysaccharides, or caffeine can improve blood lipid and antioxidant levels, and effectively reduce rat serum leptin levels, inhibit the absorption of fatty acids, and markedly reduce the expression levels of the IL-6 and TNF-α gene. Furthermore, it was shown that polysaccharides and polyphenols were synergistic in reduction of serum leptin levels and in anti-inflammatory activity. These results suggest that the polysaccharide combination with polyphenols might be a potential therapy against obesity.
158 citations
TL;DR: Generally, Dianqing Tea, Lushan Yunwu Tea, and Xihu Longjing Tea showed the strongest antioxidant activities among 30 teas, with catechins most commonly detected, especially in green tea infusions, which were main contributors to their antioxidant activities.
Abstract: Tea is among the most consumed drink worldwide, and its strong antioxidant activity is considered as the main contributor to several health benefits, such as cardiovascular protection and anticancer effect. In this study, the antioxidant activities of 30 tea infusions, which were obtained by the mimic of drinking tea of the public, from green, black, oolong, white, yellow and dark teas, were evaluated using ferric-reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays, ranging from 504.80 ± 17.44 to 4647.47 ± 57.87 µmol Fe2+/g dry weight (DW) and 166.29 ± 24.48 to 2532.41 ± 50.18 µmol Trolox/g DW, respectively. Moreover, their total phenolic contents (TPC) were detected by Folin-Ciocalteu assay and were in the range of 24.77 ± 2.02 to 252.65 ± 4.74 mg gallic acid equivalent (GAE)/g DW. Generally, Dianqing Tea, Lushan Yunwu Tea, and Xihu Longjing Tea showed the strongest antioxidant activities among 30 teas. Furthermore, the phenolic compounds in tea infusions were identified and quantified, with catechins most commonly detected, especially in green tea infusions, which were main contributors to their antioxidant activities. Besides tea polyphenols, considerable content of caffeine also presented in 30 tea infusions.
127 citations
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TL;DR: The factors underlying the influence of the different classes of polyphenols in enhancing their resistance to oxidation are discussed and support the contention that the partition coefficients of the flavonoids as well as their rates of reaction with the relevant radicals define the antioxidant activities in the lipophilic phase.
8,513 citations
TL;DR: The diversity and multiple mechanisms of flavonoid action, together with the numerous methods of initiation, detection and measurement of oxidative processes in vitro and in vivo offer plausible explanations for existing discrepancies in structure-activity relationships.
Abstract: Flavonoids are a class of secondary plant phenolics with significant antioxidant and chelating properties. In the human diet, they are most concentrated in fruits, vegetables, wines, teas and cocoa. Their cardioprotective effects stem from the ability to inhibit lipid peroxidation, chelate redox-active metals, and attenuate other processes involving reactive oxygen species. Flavonoids occur in foods primarily as glycosides and polymers that are degraded to variable extents in the digestive tract. Although metabolism of these compounds remains elusive, enteric absorption occurs sufficiently to reduce plasma indices of oxidant status. The propensity of a flavonoid to inhibit free-radical mediated events is governed by its chemical structure. Since these compounds are based on the flavan nucleus, the number, positions, and types of substitutions influence radical scavenging and chelating activity. The diversity and multiple mechanisms of flavonoid action, together with the numerous methods of initiation, detection and measurement of oxidative processes in vitro and in vivo offer plausible explanations for existing discrepancies in structure-activity relationships. Despite some inconsistent lines of evidence, several structure-activity relationships are well established in vitro. Multiple hydroxyl groups confer upon the molecule substantial antioxidant, chelating and prooxidant activity. Methoxy groups introduce unfavorable steric effects and increase lipophilicity and membrane partitioning. A double bond and carbonyl function in the heterocycle or polymerization of the nuclear structure increases activity by affording a more stable flavonoid radical through conjugation and electron delocalization. Further investigation of the metabolism of these phytochemicals is justified to extend structure-activity relationships (SAR) to preventive and therapeutic nutritional strategies.
3,567 citations
TL;DR: Some of the recent advances in flavonoid research are reviewed and the role of anthocyanins and flavones in providing stable blue flower colours in the angiosperms is outlined.
3,465 citations
TL;DR: In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture as mentioned in this paper.
1,826 citations
TL;DR: Although all the evidence from research on green tea is very promising, future studies are necessary to fully understand its contributions to human health, and advise its regular consumption in Western diets, in which green tea consumption is nowadays limited and sporadic.
Abstract: Tea is the most consumed drink in the world after water. Green tea is a 'non-fermented' tea, and contains more catechins, than black tea or oolong tea. Catechins are in vitro and in vivo strong antioxidants. In addition, its content of certain minerals and vitamins increases the antioxidant potential of this type of tea. Since ancient times, green tea has been considered by the traditional Chinese medicine as a healthful beverage. Recent human studies suggest that green tea may contribute to a reduction in the risk of cardiovascular disease and some forms of cancer, as well as to the promotion of oral health and other physiological functions such as anti-hypertensive effect, body weight control, antibacterial and antivirasic activity, solar ultraviolet protection, bone mineral density increase, anti-fibrotic properties, and neuroprotective power. Increasing interest in its health benefits has led to the inclusion of green tea in the group of beverages with functional properties. However, although all the evidence from research on green tea is very promising, future studies are necessary to fully understand its contributions to human health, and advise its regular consumption in Western diets, in which green tea consumption is nowadays limited and sporadic.
1,732 citations