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      Chemistry and health beneficial effects of oolong tea and theasinensins

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      Food Science and Human Wellness
      Elsevier BV

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          Antioxidant Activity of Various Tea Extracts in Relation to Their Antimutagenicity

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            Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions.

            Increasing interest in the health benefits of tea has led to the inclusion of tea extracts in dietary supplements and functional foods. However, epidemiologic evidence regarding the effects of tea consumption on cancer and cardiovascular disease risk is conflicting. While tea contains a number of bioactive chemicals, it is particularly rich in catechins, of which epigallocatechin gallate (EGCG) is the most abundant. Catechins and their derivatives are thought to contribute to the beneficial effects ascribed to tea. Tea catechins and polyphenols are effective scavengers of reactive oxygen species in vitro and may also function indirectly as antioxidants through their effects on transcription factors and enzyme activities. The fact that catechins are rapidly and extensively metabolized emphasizes the importance of demonstrating their antioxidant activity in vivo. In humans, modest transient increases in plasma antioxidant capacity have been demonstrated following the consumption of tea and green tea catechins. The effects of tea and green tea catechins on biomarkers of oxidative stress, especially oxidative DNA damage, appear very promising in animal models, but data on biomarkers of in vivo oxidative stress in humans are limited. Larger human studies examining the effects of tea and tea catechin intake on biomarkers of oxidative damage to lipids, proteins, and DNA are needed.
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              Effect of tea phenolics and their aromatic fecal bacterial metabolites on intestinal microbiota.

              Tea is rich in polyphenols and other phenolics that have been widely reported to have beneficial health effects. However, dietary polyphenols are not completely absorbed from the gastrointestinal tract and are metabolized by the gut microflora so that they and their metabolites may accumulate to exert physiological effects. In this study, we investigated the influence of the phenolic components of a tea extract and their aromatic metabolites upon bacterial growth. Fecal homogenates containing bacteria significantly catalyzed tea phenolics, including epicatechin, catechin, 3-O-methyl gallic acid, gallic acid and caffeic acid to generate aromatic metabolites dependent on bacterial species. Different strains of intestinal bacteria had varying degrees of growth sensitivity to tea phenolics and metabolites. Growth of certain pathogenic bacteria such as Clostridium perfringens, Clostridium difficile and Bacteroides spp. was significantly repressed by tea phenolics and their derivatives, while commensal anaerobes like Clostridium spp., Bifidobacterium spp. and probiotics such as Lactobacillus sp. were less severely affected. This indicates that tea phenolics exert significant effects on the intestinal environment by modulation of the intestinal bacterial population, probably by acting as metabolic prebiotics. Our observations provide further evidence for the importance of colonic bacteria in the metabolism, absorption and potential activity of phenolics in human health and disease. The bioactivity of different phenolics may play an important role in the maintenance of gastrointestinal health.
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                Author and article information

                Journal
                Food Science and Human Wellness
                Food Science and Human Wellness
                Elsevier BV
                22134530
                December 2015
                December 2015
                : 4
                : 4
                : 133-146
                Article
                10.1016/j.fshw.2015.10.002
                35179170
                3d561804-44f6-4494-b1aa-bdf69b885121
                © 2015
                History

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