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Selective oxidation of pyrogallol-type catechins with unripe fruit homogenate of Citrus unshiu and structural revision of oolongtheanins


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Title: Selective oxidation of pyrogallol-type catechins with unripe fruit homogenate of Citrus unshiu and structural revision of oolongtheanins
Authors: Matsuo, Yosuke / Tadakuma, Fumiya / Shii, Takuya / Saito, Yoshinori / Tanaka, Takashi
Issue Date: 29-Apr-2015
Publisher: Elsevier Limited
Citation: Tetrahedron, 71(17), pp.2540-2548; 2015
Abstract: In our previous chemical study of the production mechanism of black tea polyphenols, we demonstrated that Japanese pear fruit homogenate oxidizes green tea catechins bearing pyrogallol-type and catechol-type B-rings to produce theaflavins and dehydrotheasinensins. In contrast, unripe fruit homogenate of Citrus unshiu selectively oxidizes pyrogallol-type catechins to yield only dehydrotheasinensins. The difference in the selectivity of the two homogenates is probably related to the lower redox potential of pyrogallol-type catechins. The oxidation of epigallocatechin with C. unshiu homogenate gave two new compounds, including an ethanol adduct of an oolongtheanin precursor and epigallocatechin 4′-O-rutinoside, together with theasinensin C, dehydrotheasinensin E, and desgalloyl oolongtheanin. The structure of desgalloyl oolongtheanin should be revised based on the spectroscopic and computational data collected in the current study, and a mechanism responsible for the production of oolongtheanins is also proposed.
Keywords: Black tea / Catechin / Citrus unshiu / Oolongtheanins / Oxidation
URI: http://hdl.handle.net/10069/35841
ISSN: 00404020
DOI: 10.1016/j.tet.2015.03.016
Rights: © 2015 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Type: Journal Article
Text Version: author
Appears in Collections:Articles in academic journal

Citable URI : http://hdl.handle.net/10069/35841

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