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Enzymatic oxidation of ellagitannin and a new ellagitannin metabolite from Camellia japonica leaves

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Title: Enzymatic oxidation of ellagitannin and a new ellagitannin metabolite from Camellia japonica leaves
Authors: Tsujita, Takaaki / Matsuo, Yosuke / Saito, Yoshinori / Tanaka, Takashi
Issue Date: 2-Feb-2017
Publisher: Elsevier Ltd.
Citation: Tetrahedron, 73(5), pp.500-507; 2017
Abstract: Polyphenols in the leaves of Camellia japonica L. at different stages of growth were analyzed by HPLC. Pedunculagin [2,3; 4,6-bis-(S)-hexahydroxydiphenoyl-D-glucose] was the major polyphenol in the youngest leaves. The levels of this compound and (+)-catechin decreased as the leaves matured. The level of (−)-epicatechin did not change with leaf maturity. Enzymatic oxidation of pedunculagin was examined to investigate the mechanism of the decrease. Pedunculagin was not directly oxidized by treatment with oxidative enzymes. However, when (+)-catechin was added to the reaction mixture, the pyrogallol rings of the 4,6-hexahydroxydiphenoyl group was oxidatively cleaved to give 2H-2-oxo-pyran-6-carboxylic acid. The in vitro oxidation products were not detected in fresh leaves, but two pedunculagin oxidation products conjugated with flavan-3-ol were isolated. A new metabolite, camelliatannin I, was isolated and characterized by spectroscopic and density functional theory calculation of NMR chemical shifts.
Keywords: 2H-2-Oxo-pyran-6-carboxylic acid / Camellia japonica / Camelliatannin / Catechin / Ellagitannin / Oxidation
URI: http://hdl.handle.net/10069/37424
ISSN: 00404020
DOI: 10.1016/j.tet.2016.12.027
Rights: © 2016 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/10069/37424

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