Everything about Polyphenol totally explained
Polyphenols are a group of chemical substances found in plants, characterized by the presence of more than one
phenol unit or building block per molecule. Polyphenols are generally divided into hydrolyzable
tannins (
gallic acid esters of
glucose and other sugars) and
phenylpropanoids, such as
lignins,
flavonoids, and condensed tannins.
Chemistry
Classification and Nomenclature
The division of polyphenols into tannins, lignins, and flavonoids is derived from the variety of simple polyphenolic units derived from secondary plant metabolism of the
shikimate pathway as well as classical divisions based upon the relative importance of each base component to different fields of study. Tannin chemistry originated in the importance of
tannic acid to the
tanning industry; lignins to the chemistry of
soil and plant structure; and flavonoids to the chemistry of plant secondary metabolites for
plant defense, and flower color (for example from
anthocyanins).
The largest and best studied polyphenols are the flavonoids, which include several thousand compounds, among them the
flavonols,
flavones,
catechins,
flavanones,
anthocyanidins, and
isoflavonoids.
The most abundant polyphenols are the condensed tannins, found in virtually all families of plants, and comprising up to 50% of the dry weight of leaves. The convergent evolution of tannin-rich plant communities has occurred on nutrient-poor acidic soils throughout the world. Tannins were once believed to function as anti-herbivore defenses, but more and more ecologists now recognize them as important controllers of decomposition and nitrogen cycling processes. As concern grows about global warming, there's great interest to better understand the role of polyphenols as regulators of carbon cycling, particularly in northern boreal forests.
Polyphenols are also classified by the type and number of phenolic subcomponents present. More than one subcomponent can be present on a given polyphenol.
The phenolic unit can often be
esterified or
methylated. It can also 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 which also results in the large class of brown
thearubigins in tea.
In Foods
Notable sources of polyphenols include
berries,
tea,
beer,
grapes/
wine,
olive oil,
chocolate/
cocoa,
walnuts,
peanuts,
pomegranates,
yerba mate, and other
fruits and
vegetables.
High levels of polyphenols can generally be found in the fruit skins.
Health benefits
Polyphenols were once briefly known as Vitamin P. However they were quickly found out to be non-essential and reclassified. The health benefits of specific polyphenols such as
quercetin are well-established, there are less well-established claims of health benefits from all types of polyphenols.
Research indicates that polyphenols may have
antioxidant characteristics with potential health benefits. They may reduce the risk of cardiovascular disease and cancer.
Polyphenols have also been investigated as a source of additional health benefit in organic produce, but no conclusion was made.
Polyphenols bind with nonheme iron (for example from plant sources)
in vitro in model systems.
This may decrease its absorption by the body.
Further Information
Get more info on 'Polyphenol'.
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