Oxidation Mechanism of Polyphenols and Chemistry of Black Tea

Matsuo, Yosuke; Tanaka, Takashi

doi:10.1002/9781118883303.ch3

Cited by 6 publications

(4 citation statements)

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“…A total of 60-80% of the total tea catechins possess galloyl esters located at the C-3 hydroxy group and oxidation of galloyl groups may be important to the formation of black tea pigment [26]; only limited examples of oxidative coupling of galloyl groups have been reported [17,[27][28][29]. Besides, enzymes preferentially oxidize the catechol B-rings, and the resulting quinone subsequently oxidizes the pyrogallol rings for the redox potential of which is lower than that of the catechol rings [30][31][32][33]. The four major theaflavins are theaflavin, theaflavin 3-gallate, theaflavin 3′-gallate and theaflavin 3,3′-digallate, which are formed by coupling between EC and EGC, EC and EGCG, EGC and EGC, and EGC and EGCG, respectively.…”

Section: Benzotroplone Derivates In Teamentioning

confidence: 99%

“…The four major theaflavins are theaflavin, theaflavin 3-gallate, theaflavin 3′-gallate and theaflavin 3,3′-digallate, which are formed by coupling between EC and EGC, EC and EGCG, EGC and EGC, and EGC and EGCG, respectively. Stereoisomers of theaflavin and their closely related benzotropolone compounds such as neo-theaflavins, iso-theafla vins, theaflavate, theaflavic acids, and methylated theaflavins, etc., have also been identi fied from black tea [31][32][33][34]. They are shown in Figure 4.…”

Section: Benzotroplone Derivates In Teamentioning

confidence: 99%

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Enzymatic Oxidation of Tea Catechins and Its Mechanism

Abudureheman

Dai

et al. 2022

Molecules

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Tea (Camellia sinensis, Theaceae) is one of the most widely consumed beverages in the world. The three major types of tea, green tea, oolong tea, and black tea, differ in terms of the manufacture and chemical composition. Catechins, theaflavins, and thearubigins have been identified as the major components in tea. Other minor oligomers have also been found in tea. Different kinds of ring fission and formation elucidate the major transformed pathways of tea catechins to their dimers and polymers. The present review summarizes the data concerning the enzymatic oxidation of catechins, their dimers, and thearubigins in tea.

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Section: Benzotroplone Derivates In Teamentioning

confidence: 99%

Section: Benzotroplone Derivates In Teamentioning

confidence: 99%

Enzymatic Oxidation of Tea Catechins and Its Mechanism

Abudureheman

Dai

et al. 2022

Molecules

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“…4 . The physiological meaning of the reactions occurring on the wound surface is not clear; however, the polymerization of procyanidins is probably related to the defense system, because in some plants such as tea leaves the enzymatic oxidation of polyphenols accompanies the production of oligomers and polymers in response to wounding 16,17 . Furthermore, pigment formation by oxidation with oxygen molecules is possibly accompanied by the production of reactive oxygen species, such as a superoxide anion radical or hydrogen peroxide, which exhibits antibacterial activity 31 .…”

Section: Polymeric Pigments Produced From Cinnamon Procy-mentioning

confidence: 99%

Solubility of Tannins and Preparation of Oil-Soluble Derivatives

2018

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INTRODUCTION Tannins are a group of plant polyphenols that can precipitate proteins and heavy metals in aqueous solutions 1. The precipitation of salivary proteins in oral cavities via interaction with tannins leads to an unpleasant astringent taste, and interactions of tannins with digestive enzymes decrease absorption of sugar and lipid from the digestive tract 2, 3. Ironically, the decreased uptake of sugar and lipid from the digestive tract has been recognized as health benefits of tannins in developed countries for the prevention of diabetes and hyperlipidemia 4 6. Tannins suppress the proliferation of microorganisms and exhibit antioxidative activities similar to other polyphenols such as flavonol and hydroxycinnamate. Based on these physicochemical and biological properties, in addition to previously reported results in chemical ecology, it is generally accepted that tannins are plant defense substances 7, 8. In addition, the wide distribution of tannins in the plant kingdom including ferns, gymnosperms, and angiosperms, suggests that plants began to biosynthesize tannins in the early stage of plant evolution 9. However, in the current stage of evolution, the toxicity of tannins is considerably weaker than those of sophisticated toxic alkaloids and terpenoids, and herbivores, including humans, can cope with the toxicity of tannins 10. Many herbivorous mammals synthesize and secrete a group of proline-rich peptides in the saliva with a high affinity for

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“…Oligomeric proanthocyanidins (OPAs) constitute a huge class of natural products with potential bioactivities. 1 Among the origins of the structure diversity is the variation of constituent monomers, as manifested in procyanidin B3 ( 1 ) and B4 ( 2 ), which are a catechin–catechin homo-dimer and a catechin–epicatechin hetero-dimer, respectively (Fig. 1).…”

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confidence: 99%