Editing Polyphenol (section)

==Definition==
[[File:Ellagic acid.svg|thumb|right|[[Ellagic acid]], a polyphenol]]

Polyphenols are [[natural product]]s with "one or several [[hydroxyl groups]] on [[aromatic ring]]s",  including four principal classes: phenolic acids, flavonoids, [[stilbene]]s, and [[lignan]]s.<ref name=lpi/><ref name="manach">{{cite journal | vauthors = Manach C, Scalbert A, Morand C, Rémésy C, Jiménez L | title = Polyphenols: food sources and bioavailability | journal = The American Journal of Clinical Nutrition | volume = 79 | issue = 5 | pages = 727–747 | date = May 2004 | pmid = 15113710 | doi = 10.1093/ajcn/79.5.727 | doi-access = free }}</ref> Flavonoids can be grouped as flavones, flavonols, flavanols, flavanones, isoflavones, [[proanthocyanidin]]s, and anthocyanins.<ref name=lpi/> Particularly abundant flavanoids in foods are [[catechin]] (tea, fruits), [[hesperetin]] (citrus fruits), [[cyanidin]] (red fruits and berries), [[daidzein]] ([[soybean]]), proanthocyanidins (apple, grape, cocoa), and [[quercetin]] (onion, tea, apples).<ref name="lpi" /> Polyphenols also include phenolic acids, such as [[caffeic acid]], and lignans, which are derived from phenylalanine present in [[flax]] seed and other cereals.<ref name=lpi/>

===WBSSH definition===

The White–Bate-Smith–Swain–Haslam (WBSSH) definition<ref name="Haslam_and_Cai">{{cite journal | vauthors = Haslam E, Cai Y | title = Plant polyphenols (vegetable tannins): gallic acid metabolism | journal = Natural Product Reports | volume = 11 | issue = 1 | pages = 41–66 | date = January 1994 | pmid = 15206456 | doi = 10.1039/NP9941100041 }}</ref> characterized structural characteristics common to plant phenolics used in [[Tanning (leather)|tanning]] (i.e., the tannins).<ref>Practical Polyphenolics, Edwin Haslam, 1998, {{ISBN|0-521-46513-3}}</ref>

In terms of properties, the WBSSH describes the polyphenols as follows:
* generally moderately [[water-soluble]] compounds
* with molecular weight of 500–4000 Da
* with >12 phenolic hydroxyl groups
* with 5–7 aromatic rings per 1000 Da
In terms of structures, the WBSSH recognizes two structural family that have these properties:
* proanthocyanidins and its derivatives
* [[gallic acid|galloyl]] and hexahydroxydiphenoyl esters and their derivatives

===Quideau definition===
[[File:Raspberry ellagitannin.png|thumb|upright=1.35|right|[[Raspberry ellagitannin]], a [[tannin]] composed of 14 gallic acid units around a core of three units of glucose, with two gallic acids as simple esters, and the remaining 12 appearing in 6 ellagic acid-type units. Ester, ether, and biaryl linkages are present, see below.]]

According to Stéphane Quideau, the term "polyphenol" refers to compounds derived from the [[shikimate]]/phenylpropanoid and/or the [[polyketide]] pathway, featuring more than one phenolic unit and deprived of nitrogen-based functions.{{Citation needed|date=July 2021}}

[[Ellagic acid]], a molecule at the core of naturally occurring phenolic compounds of varying sizes, is itself not a polyphenol by the WBSSH definition, but is by the Quideau definition. The [[raspberry ellagitannin]],<ref>{{Cite web |url=http://www.scri.ac.uk/scri/image/Research/qhn/cardiovascular/Raspberry-Ellagitannin.jpg|title=Cardiovascular disease and phytochemicals. Anonymous. C. Hamilton et al.}}</ref> on the other hand, with its 14 [[gallic acid]] moieties (most in ellagic acid-type components), and more than 40 phenolic hydroxyl groups, meets the criteria of both definitions of a polyphenol. Other examples of compounds that fall under both the WBSSH and Quideau definitions include the [[black tea]] [[theaflavin-3-gallate]] shown below, and the hydrolyzable tannin, [[tannic acid]].{{Citation needed|date=July 2021}}