Editing Tannin (section)

== Structure and classes of tannins ==
There are three major classes of tannins: Shown below are the base unit or monomer of the tannin. Particularly in the flavone-derived tannins, the base shown must be (additionally) heavily hydroxylated and polymerized in order to give the high molecular weight [[polyphenol]] motif that characterizes tannins. Typically, tannin molecules require at least 12 hydroxyl groups and at least five phenyl groups to function as protein binders.<ref name="ref 1">{{Cite web|url=http://pharmaxchange.info/notes/cognosy/tannins.html|archive-url=https://web.archive.org/web/20150104040231/http://pharmaxchange.info/notes/cognosy/tannins.html|url-status=dead|title=Notes on Tannins from PharmaXChange.info|archive-date=4 January 2015}}</ref>

{| class="wikitable"
|- style="text-align:center;"
!scope=row|Base unit / scaffold
|[[File:Gallic acid.svg|x100px]]<br />[[Gallic acid]]
|[[File:Phloroglucin.svg|x100px]]<br />[[Phloroglucinol]]
| colspan="2" |[[File:Flavan-3-ol.svg|x100px]]<br />[[Flavan-3-ol]]
|-
!scope=row|Polymer class
|[[Hydrolyzable tannin]]s
|[[Phlorotannin]]s
|[[Condensed tannin]]s<ref name=":0">{{cite book |title=Chemistry and Significance of Condensed Tannins |author=Richard W. Hemingway |author2=Joseph J. Karchesy |page=113 |isbn=978-1-4684-7511-1}}</ref>
|[[Phlobatannin]]s (C-ring isomerized condensed tannins)<ref name=":0" />
|-
!Sources
|Plants
|[[Brown algae]]
|Plants
|Tree heartwood 
|}
[[Oligostilbenoid]]s (oligo- or polystilbenes) are oligomeric forms of [[stilbenoid]]s and constitute a minor class of tannins.<ref>{{cite journal | last1 = Boralle | first1 = N. | last2 = Gottlieb | first2 = H. E. | last3 = Gottlieb | first3 = O. R. | last4 = Kubitzki | first4 = K. | last5 = Lopes | first5 = L. M. X. | last6 = Yoshida | first6 = M. | last7 = Young | first7 = M. C. M. | year = 1993 | title = Oligostilbenoids from ''Gnetum venosum'' | journal = Phytochemistry | volume = 34 | issue = 5| pages = 1403–1407 | doi=10.1016/0031-9422(91)80038-3 | bibcode = 1993PChem..34.1403B }}</ref>

=== Pseudo-tannins<span class="anchor" id="Pseudo tannins"></span> ===
Pseudo-tannins are low molecular weight compounds associated with other compounds. They do not change color during the [[Goldbeater's skin]] [[#Tests for tannins|test]], unlike hydrolysable and condensed tannins, and cannot be used as tanning compounds.<ref name="ref 1" /> Some examples of pseudo tannins and their sources are:<ref>{{cite book|author=Ashutosh Kar|title=Pharmacognosy And Pharmacobiotechnology|url=https://books.google.com/books?id=PlMi4XvHCYoC&pg=PA44|access-date=31 January 2011|year=2003|publisher=New Age International|isbn=978-81-224-1501-8|pages=44–|url-status=live|archive-url=https://web.archive.org/web/20130602035552/http://books.google.com/books?id=PlMi4XvHCYoC&pg=PA44|archive-date=2 June 2013|df=dmy-all}}</ref>

{| class="wikitable"
|-
! Pseudo tannin !! Source(s)
|-
| [[Gallic acid]] || [[Rhubarb]]
|-
| [[Flavan-3-ol]]s (''Catechins'') || [[Camellia sinensis|Tea]], [[acacia]], [[catechu]], [[Theobroma cacao|cocoa]], [[guarana]]
|-
| [[Chlorogenic acid]] || [[Nux vomica (herbalism)|Nux-vomica]], [[coffee]], [[Mate (beverage)|mate]]
|-
| Ipecacuanhic acid || ''[[Carapichea ipecacuanha]]''
|}