- A novel black tea pigment and two new oxidation products of epigallocatechin-3-O-gallate
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During tea fermentation, oxidation-reduction dismutation of a number of quinone metabolites of tea catechins yields numerous minor products, which make it difficult to separate and purify black tea polyphenols. In this study, epigallocatechin-3-O-gallate
- Tanaka, Takashi,Matsuo, Yosuke,Kouno, Isao
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- Biomimetic one-pot preparation of a black tea polyphenol theasinensin A from epigallocatechin gallate by treatment with copper(II) chloride and ascorbic acid
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Chromatographic separation of black tea polyphenols is too difficult to supply sufficient quantities of pure compounds for biological experiments. Thus, facile methods to prepare black tea constituents were desired. Treatment of epigallocatechin gallate w
- Shii, Takuya,Miyamoto, Makoto,Matsuo, Yosuke,Tanaka, Takashi,Kouno, Isao
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experimental part
p. 1183 - 1185
(2011/10/30)
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- Production of theasinensins A and D, epigallocatechin gallate dimers of black tea, by oxidation-reduction dismutation of dehydrotheasinensin A
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Theasinensins A and D are B,B′-linked dimers of (-)-epigallocatechin 3-O-gallate connected through R and S biphenyl bonds, respectively, and are major constituents of black tea. Enzymatic oxidation of epigallocatechin 3-O-gallate produced dehydrotheasinensin A, and the structure was shown to be equivalent to an o-quinone of theasinensin A. When the aqueous solution of dehydrotheasinensin A was heated, theasinensin D was produced along with galloyl oolongtheanin. On the other hand, dehydrotheasinensin A was converted to theasinensins A and D along with oxidation products in phosphate buffer at pH 6.8 at room temperature. The results strongly suggested that theasinensins in black tea were produced by oxidation-reduction dismutation of dehydrotheasinensin.
- Tanaka, Takashi,Watarumi, Sayaka,Matsuo, Yosuke,Kamei, Midori,Kouno, Isao
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p. 7939 - 7947
(2007/10/03)
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- Tannins and Related Compounds. LXIX. Isolation and Structure Elucidation of B,B'-Linked Bisflavanoids, Theasinensins D-G and Oolongtheanin from Oolong Tea. (2)
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Chemical examination of the aqueous acetone extract of commercial oolong tea has led to the isolation of four new theasinensins D-G, and a new type of dimeric flavan-3-ol named oolongtheanin, together with previously reported theasinensins A, B, and C.On the basis of chemical and spectroscopic evidence, theasinensins D and E were characterized as atropisomers (4 and 5) of theasinensins A (1) and C (3), respectively, while theasinensins F and G were shown to be B,B'-linked bisflavanoids (6 and 7) consisting of (-)-epicatechin 3-O-gallate and (-)-epigallocatechin 3-O-gallate units, in which the biphenyl bonds possess S- and R-chiralities, respectively.Similarly, oolongtheanin was characterized as a novel metabolite (8), probably derived from theasinensins by oxidation of one of the B-rings.Keywords - oolong tea; Camellia sinensis var. viridis; Theaceae; polyphenol; theasinensin; oolongtheanin; oxidative metabolite; bisflavanoid; flavan-3-ol; fermentation.
- Hashimoto, Fumio,Nonaka, Gen-Ichiro,Nishioka, Itsuo
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p. 1676 - 1684
(2007/10/02)
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