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Reductive Metabolism of Ellagitannins in the Young Leaves of Castanopsis sieboldii

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Title: Reductive Metabolism of Ellagitannins in the Young Leaves of Castanopsis sieboldii
Authors: Wakamatsu, Hatsumi / Tanaka, Sumire / Matsuo, Yosuke / Saito, Yoshinori / Nishida, Koyo / Tanaka, Takashi
Issue Date: 24-Nov-2019
Publisher: MDPI
Citation: Molecules, 24(23), art.no.4279; 2019
Abstract: The leaves of Castanopsis sieboldii (Fagaceae) contain characteristic hexahydroxydiphenoyl (HHDP) esters of 28-O-glucosyl 2α,3β,23,24-tetrahydroxyolean- and urs-12-en-28-oic acids. In this study, uncharacterized substances were detected in the young leaves, which are not observed in the mature leaves. Preliminary HPLC analyses indicated that the substances had dehydro-HHDP (DHHDP) ester groups; however, the esters were unstable and decomposed during extraction. Therefore, the compounds were isolated as their stable phenazine derivatives by extracting the young leaves with acidic aqueous EtOH containing o-phenylenediamine. The structures of the phenazine derivatives indicated that the unstable metabolites of the young leaves were 3,24-DHHDP esters of the abovementioned triterpenes. Extraction of the young leaves with 80% acetonitrile containing reducing agents, ascorbic acid or dithiothreitol afforded the corresponding HHDP esters. Furthermore, heating of the young leaves in 80% acetonitrile also yielded the same HHDP esters as the reduction products. The results suggested that the HHDP esters are reductively produced from DHHDP esters in the young leaves. In addition, the structures of five previously reported triterpene HHDP esters were revised.
Keywords: Castanopsis sieboldii / dehydrohexahydroxydiphenoyl / ellagitannin / hexahydroxydiphenoyl / triterpene
URI: http://hdl.handle.net/10069/39574
DOI: 10.3390/molecules24234279
Rights: © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Type: Journal Article
Text Version: publisher
Appears in Collections:Articles in academic journal

Citable URI : http://hdl.handle.net/10069/39574

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