4670-05-7Relevant articles and documents
Accumulation of epigallocatechin quinone dimers during tea fermentation and formation of theasinensins
Tanaka, Takashi,Mine, Chie,Watarumi, Sayaka,Fujioka, Toshihiro,Mihashi, Kunihide,Zhang, Ying-Jun,Kouno, Isao
, p. 1582 - 1587 (2002)
Production and accumulation of catechin dimer quinones during tea fermentation were chemically confirmed for the first time by trapping as phenazine derivatives. Direct treatment of the fermented tea leaves with o-phenylenediamine yielded five phenazine derivatives (8-12) of o-quinones of an epigallocatechin dimer and its galloyl esters (13-16), in which two flavan units were linked at the B-rings through a C-C bond. Atrop isomerism of the biphenyl bonds was shown to be the R configuration, suggesting that the o-quinone dimers were generated by stereoselective coupling of monomeric quinones. The total concentration of the phenazine derivatives in the o-phenylenediamine-treated tea leaves was higher than that of theaflavins. In contrast, phenazine derivatives of monomeric quinones of epigallocatechin were not isolated. When the fermented tea leaves were heated, the quinone dimers were converted to theasinensins, which are constituents of black tea, suggesting that theasinensins are generated by reduction of the quinone dimers during the heating and drying steps in black tea manufacturing.
Nonenzymatic Biomimetic Synthesis of Black Tea Pigment Theaflavins
Matsuo, Yosuke,Oowatashi, Ryosuke,Saito, Yoshinori,Tanaka, Takashi
supporting information, p. 2505 - 2508 (2017/10/06)
Theaflavins are reddish-orange black tea pigments with a benzotropolone chromophore, and their various biological activities have been reported. Theaflavins are produced by oxidative coupling between catechol-type and pyrogallol-type catechins via bicyclo[3.2.1]octane-type intermediates. In this study, a new method for nonenzymatic biomimetic synthesis of theaflavins was developed using the DPPH radical as an oxidizing agent.
Syntheses of methylated catechins and theaflavins using 2-nitrobenzenesulfonyl group to protect and deactivate phenol
Asakawa, Tomohiro,Kawabe, Yusuke,Yoshida, Atsushi,Aihara, Yoshiyuki,Manabe, Tamiko,Hirose, Yoshitsugu,Sakurada, Asuka,Inai, Makoto,Hamashima, Yoshitaka,Furuta, Takumi,Wakimoto, Toshiyuki,Kan, Toshiyuki
, p. 299 - 312 (2016/05/09)
An efficient and versatile synthetic method for labile polyphenols was established using 2-nitrobenzenesulfonate (Ns) as a protecting group for phenol. This methodology provides regio-and stereoselective access to a range of methylated catechins, such as methylated epigallocatechin gallates, that are not readily available from natural sources. In addition, biomimetic synthesis of theaflavins from catechins was accomplished using Ns protection to minimize undesired side reactions of electron-rich aromatic rings during oxidation, enabling construction of the complex benzotropolone core in a single-step oxidative coupling reaction. Availability of these compounds will aid detailed structure-biological activity relationship studies of catechins.
Oxidation mechanism of black tea pigment theaflavin by peroxidase
Kusano, Rie,Matsuo, Yosuke,Saito, Yoshinori,Tanaka, Takashi
, p. 5099 - 5102 (2015/08/06)
A large number of black tea polyphenols remain uncharacterized because of the complexity of catechin oxidation reactions that occur during tea fermentation. In the course of our studies on black tea polyphenols, we examined the enzymatic degradation of theaflavins, which are black tea pigments having a benzotropolone chromophore. Oxidation of theaflavin with peroxidase afforded a new product named theacoumarin A together with known pigment theanaphthoquinone. The structure of the new compound was determined by spectroscopic examination and a production mechanism via theanaphthoquinone is proposed.