The ellagitannins are a diverse class of
hydrolyzable tannins, a type of
polyphenol
Polyphenols () are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some o ...
formed primarily from the oxidative linkage of
galloyl groups in
1,2,3,4,6-pentagalloyl glucose. Ellagitannins differ from
gallotannins, in that their
galloyl groups are linked through C-C bonds, whereas the galloyl groups in gallotannins are linked by
depside bonds.
Ellagitannins contain various numbers of
hexahydroxydiphenoyl units, as well as
galloyl units and/or
sanguisorboyl units bounded to sugar moiety. In order to determine the quantity of every individual unit, the hydrolysis of the extracts with
trifluoroacetic acid
Trifluoroacetic acid (TFA) is an organofluorine compound with the chemical formula CF3CO2H. It is a structural analogue of acetic acid with all three of the acetyl group's hydrogen atoms replaced by fluorine atoms and is a colorless liquid with ...
in
methanol/water system is performed. Hexahydroxydiphenic acid, created after hydrolysis, spontaneously lactonized to
ellagic acid
Ellagic acid is a polyphenol found in numerous fruits and vegetables. It is the dilactone of hexahydroxydiphenic acid.
Name
The name comes from the French term ''acide ellagique'', from the word ''galle'' spelled backwards because it can be o ...
, and
sanguisorbic acid to sanguisorbic acid dilactone, while
gallic acid
Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants ...
remains intact.
Ellagitannins generally form
macrocycles, whereas gallotannins do not.
Examples
*
Castalagin
*
Castalin
Castalin is an ellagitannin. It can be found in oak wood and in ''Melaleuca quinquenervia
''Melaleuca quinquenervia'', commonly known as the broad-leaved paperbark, paper bark tea tree, punk tree or niaouli, is a small- to medium-sized tree of ...
*
Casuarictin
*
Grandinin
*
Oenothein B from Willowherbs (Epilobium spp.)
*
Roburin A
*
Tellimagrandin II
*
Terflavin B
*
Vescalagin
*
Pomegranate ellagitannins, many compounds
**
Punicalagin
**
Punicalin
Metabolism
Degradation
Urolithins, such as
urolithin A, are microflora human metabolites of dietary
ellagic acid
Ellagic acid is a polyphenol found in numerous fruits and vegetables. It is the dilactone of hexahydroxydiphenic acid.
Name
The name comes from the French term ''acide ellagique'', from the word ''galle'' spelled backwards because it can be o ...
derivatives.
Natural occurrences
Ellagitannins are reported in
dicotyledoneous angiospermes, and notably in species in the order
Myrtales
The Myrtales are an order of flowering plants placed as a sister to the eurosids II clade as of the publishing of the ''Eucalyptus grandis'' genome in June 2014.
The APG III system of classification for angiosperms still places it within the eur ...
, such as the
pomegranate
The pomegranate (''Punica granatum'') is a fruit-bearing deciduous shrub in the family Lythraceae, subfamily Punicoideae, that grows between tall.
The pomegranate was originally described throughout the Mediterranean Basin, Mediterranean re ...
.
See also
*
Urolithin -
Urolithin A
*
Polyphenol
Polyphenols () are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some o ...
s
*
List of antioxidants in food
References
Further reading
* Quideau, Stéphane (editor). ''Chemistry and Biology of Ellagitannins: An Underestimated Class of Bioactive Plant Polyphenols'', 2009, World Scientific Publishing.
Table of Contents Preface
Chapter 1
External links
Tannin Chemistry
(Tannin Handbook, Copyright 1998, 2002, 2011, Ann E. Hagerman)
{{Ellagitannin
Aromatase inhibitors