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.
Specificity of tyrosinase-catalyzed synthesis of theaflavins
Narai-Kanayama, Asako,Kawashima, Aya,Uchida, Yuuka,Kawamura, Miho,Nakayama, Tsutomu
, p. S452 - S458 (2018/04/05)
This study kinetically characterized the mechanism of the enzymatic synthesis of theaflavins (TFs) from catechins by mushroom tyrosinase (EC 1.14.18.1). In reactions containing one of four catechins, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), and their galloylated forms (ECg and EGCg), they were oxidized by tyrosinase with apparent KM values of 3.78, 5.55, 0.80, and 3.05 mM, respectively, and with different consumption rates, of which EC was more than four times higher than those of the others. In reactions with binary combinations of catechins with tyrosinase, the synthesis of TF1 from EC and EGC occurred most efficiently, while the yields of mono- and di-galloylated TFs, TF2A, TF2B, and TF3, were low. Time-dependent changes in concentrations of the reactants suggested that the enzymatic oxidation of catechins and the subsequent non-enzymatic coupling redox reaction between the quinone derived from EC or ECg and the intact pyrogallol-type catechin (EGC or EGCg) proceeded concurrently. The latter reaction induced the rapid decrease of EGC and EGCg and it was remarkable for EGCg. So the efficiency of condensation of a pair of quinones from catechol- and pyrogallol-type catechins is restricted, critically influencing the yield of TFs. Using green tea extracts as mixtures of the four substrate catechins, tyrosinase produced TF1 most abundantly. Furthermore, a remarkable enhancement of production of TF2A and TF2B as well as TF1 was observed, when the initial concentration of EGCg was low. These results suggest that the catechin composition has an impact on yields of TFs.
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.