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Polyphenols (/ ˌ p ɒ l i ˈ f iː n oʊ l,-n ɒ l /) are a large family of naturally occurring phenols. [1] They are abundant in plants and structurally diverse. [1] [2] [3] Polyphenols include phenolic acids, flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.
The main source of polyphenols is dietary, since they are found in a wide array of phytochemical-bearing foods.For example, honey; most legumes; fruits such as apples, blackberries, blueberries, cantaloupe, pomegranate, cherries, cranberries, grapes, pears, plums, raspberries, aronia berries, and strawberries (berries in general have high polyphenol content [5]) and vegetables such as broccoli ...
The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds, which are more specifically termed flavanoids. The three cycles or heterocycles in the flavonoid backbone are generally called ring A, B, and C. [ 2 ] Ring A usually shows a phloroglucinol substitution pattern.
The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol. For example, ellagic acid is a dimer of gallic acid and forms the class of ellagitannins, or a catechin and a gallocatechin can combine to form the red compound theaflavin, a process that also results in the large class of brown thearubigins in tea.
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Phenolic compounds are classified as simple phenols or polyphenols based on the number of phenol units in the molecule. Phenol – the simplest of the phenols Chemical structure of salicylic acid, the active metabolite of aspirin. Phenols are both synthesized industrially and produced by plants and microorganisms. [2]
As part of their adaptation from marine life, terrestrial plants began producing non-marine antioxidants such as ascorbic acid (), polyphenols, and tocopherols.The evolution of angiosperm plants between 50 and 200 million years ago resulted in the development of many antioxidant pigments – particularly during the Jurassic period – as chemical defences against reactive oxygen species that ...
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. [4]