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Concept
Polyphenol
Summary
Polyphenols (ˌpɒliˈfiːnoʊl,_-nɒl) are a large family of naturally occurring phenols. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.
The name derives from the Ancient Greek word πολύς (polus, meaning "many, much") and the word ‘phenol’ which refers to a chemical structure formed by attachment of an aromatic benzenoid (phenyl) ring to a hydroxyl (-OH) group as is found in alcohols (hence the -ol suffix). The term "polyphenol" has been in use at least since 1894.
The term polyphenol is not well-defined, but is generally agreed that they are natural products "having a polyphenol structure (i.e., several hydroxyl groups on aromatic rings)" including four principal classes: "phenolic acids, flavonoids, stilbenes, and lignans".
Flavonoids include flavones, flavonols, flavanols, flavanones, isoflavones, proanthocyanidins, and anthocyanins. 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).
Phenolic acid include caffeic acid
Lignans are polyphenols derived from phenylalanine found in Flax seed and other cereals.
The White–Bate-Smith–Swain–Haslam (WBSSH) definition characterized structural characteristics common to plant phenolics used in tanning (i.e., the tannins).
In terms of properties, the WBSSH describes the polyphenols thusly:
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
galloyl and hexahydroxydiphenoyl esters and their derivatives
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.
Official source
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