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Tannins of Constant Structure in Medicinal and Food Plants—Hydrolyzable Tannins and Polyphenols Related to Tannins

by Takuo Okuda 1,* and Hideyuki Ito 2
1
Emeritus Professor, Okayama University, Tsushima-naka, Okayama 700, Japan
2
Division of Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima-naka, Okayama 700, Japan
*
Author to whom correspondence should be addressed.
Molecules 2011, 16(3), 2191-2217; https://doi.org/10.3390/molecules16032191
Received: 19 January 2011 / Revised: 24 February 2011 / Accepted: 28 February 2011 / Published: 4 March 2011
(This article belongs to the Special Issue Tannins)
In addition to the commonly used classification as hydrolyzable tannins and condensed tannins, tannins can also be categorized into two other types: polyphenols of constant chemical structure (Type A) and polyphenols of variable composition (Type B). Both types of tannins and related polyphenols account for a large part of plant polyphenols, but accurate structure-activity correlations on a molecular basis can be determined mainly for type A compounds, among which are hydrolysable tannins such as the ellagitannins and their oxidized congeners, some gallotannins, epigallocatechin gallate, caffetannins, etc. Among the activities determined on a molecular basis are the chemical, biological and pharmacological actions such as superoxide anion scavenging, apoptosis, antitumor, anti-EVB, anti-MRSA and anti-plasmin inhibitory activities, etc., in addition to their fundamental activities, i.e., binding to proteins, large molecular compounds and metallic ions, and antioxidant activities. Some structure-specific activities were found for the condensation of dehydroellagitannins with co-existing compounds under mild conditions, and the host-mediated antitumor actions of ellagitannin oligomers. Structures and activities of metabolites of geraniin, a dehydroellagitannin, were revealed. Some stilbenoids and phlorotannins of firm structures have been known to have many activities similar to those of the type A tannins. View Full-Text
Keywords: tannin and polyphenol; type A tannin; type B tannin; classification; biological and pharmacological properties tannin and polyphenol; type A tannin; type B tannin; classification; biological and pharmacological properties
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Okuda, T.; Ito, H. Tannins of Constant Structure in Medicinal and Food Plants—Hydrolyzable Tannins and Polyphenols Related to Tannins. Molecules 2011, 16, 2191-2217.

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