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Technological Application of Tannin-Based Extracts
Open AccessArticle

Production of Ellagitannin Hexahydroxydiphenoyl Ester by Spontaneous Reduction of Dehydrohexa-hydroxydiphenoyl Ester

Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
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Author to whom correspondence should be addressed.
Academic Editor: Teresa Escribano-Bailón; Ignacio García-Estévez
Molecules 2020, 25(5), 1051; https://doi.org/10.3390/molecules25051051
Received: 31 January 2020 / Revised: 23 February 2020 / Accepted: 24 February 2020 / Published: 26 February 2020
(This article belongs to the Special Issue Tannin Analysis, Chemistry, and Functions)
Amariin is an ellagitannin with two dehydrohexahydroxydiphenoyl (DHHDP) moieties connecting glucose 2,4- and 3,6-hydroxy groups. This tannin is predominant in the young leaves of Triadica sebifera and Carpinus japonica. However, as the leaves grow, the 3,6-DHHDP is converted to its reduced form, the hexahydroxydiphenoyl (HHDP) group, to generate geraniin, a predominant ellagitannin of the matured leaves. The purified amariin is unstable in aqueous solution, and the 3,6-(R)-DHHDP is spontaneously degraded to give HHDP, whereas 2,4-(R)-DHHDP is stable. The driving force of the selective reduction of the 3,6-DHHDP of amariin is shown to be the conformational change of glucose from O,3B to 1C4. Heating geraniin with pyridine affords 2,4-(R)-DHHDP reduction products. Furthermore, the acid hydrolysis of geraniin yields two equivalents of ellagic acid. Although the reaction mechanism is still ambiguous, these results propose an alternative biosynthetic route of the ellagitannin HHDP groups. View Full-Text
Keywords: dehydrohexahydroxydiphenic acid; hexahydroxydiphenic acid; amariin; geraniin; ellagitannin dehydrohexahydroxydiphenic acid; hexahydroxydiphenic acid; amariin; geraniin; ellagitannin
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MDPI and ACS Style

Era, M.; Matsuo, Y.; Saito, Y.; Tanaka, T. Production of Ellagitannin Hexahydroxydiphenoyl Ester by Spontaneous Reduction of Dehydrohexa-hydroxydiphenoyl Ester. Molecules 2020, 25, 1051.

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