Polyphenols

Dietary polyphenols are the most abundant antioxidants in human diets. The main dietary sources of polyphenols include many fruits and vegetables, and tea, which contains powerful antioxidant polyphenols called catechins. Green and white teas contain more catechins than black tea, and are preferred as a health drink. The root vegetable turmeric, used mainly in curry dishes, contains curcumin, a substance which is the subject of much current research because of its potential anti-cancer properties. Red grape skins, especially those which are used to produce the highly tannic wines of southwest France, contain another poweful polyphenol called resveratrol. Unfortunately reservations have been expressed regarding the amount of red wine one would have to consume in order to derive the health benefits! Fortunately resveratrol is available in capsule form from a number of supplement manufacturers, as are turmeric (curcumin) and green tea. Polyphenolic antioxidants are present in especially concentrated amounts in dark coloured fruits and vegetables, in particular dark red and deep blue berry fruits such as blueberries, blackberries and cherries. These particular phytonutrients are called anthocyanins.

Dietary polyphenols represent a wide variety of compounds that occur in fruits, vegetables, wine, tea, extra virgin olive oil, chocolate and other cocoa products. They are mostly derivatives and/or isomers of flavones, isoflavones, flavonols, catechins and phenolic acids, and possess diverse biological properties such as antioxidant, antiapoptosis, anti-aging, anticarcinogen, anti-inflammation, anti-atherosclerosis, cardiovascular protection, improvement of the endothelial function, as well as inhibition of angiogenesis and cell proliferation activity. Most of these biological actions have been attributed to their intrinsic reducing capabilities. They may also offer indirect protection by activating endogenous defense systems and by modulating cellular signaling processes. 

Oxidative stress results in oxidative alteration of biological macromolecules such as lipids, proteins and nucleic acids. It is considered to play a pivotal role in the pathogenesis of aging and several degenerative diseases, such as atherosclerosis, cardiovascular disease, type II diabetes and cancer. In order to cope with an excess of free radicals produced by oxidative stress, humans have developed endogenous and exogenous mechanisms in order to maintain redox homeostasis. Among these, dietary polyphenols have been largely studied for their strong antioxidant capacities and other properties by which cell activities are regulated. The undesired effects of oxidative stress have been found to be controlled by the antioxidant and/or anti-inflammatory effects of dietary polyphenols such as curcumin and resveratrol.

Dietary polyphenols may not merely exert their diverse biological effects as free radical scavengers, but may also modulate cellular signaling processes by affecting signal transduction pathways. Several studies have indicated that red wine polyphenolic compounds were able to inhibit proliferation and migration of vascular cells, showing vasodilatory, vasoprotective and anti-hypertensive effects of polyphenols in vivo.

Dietary polyphenols appear to have a protective effect on immune cell functions. Experiments have shown that leukocyte functions were improved in prematurely aging mice after five weeks of diet supplementation with polyphenol-rich cereals.

Dietary polyphenols could modulate diverse biochemical processes involved in carcinogenesis. Curcumin exerted antitumor activities by inhibition of cellular proliferation and angiogenesis, blockade of tumor cell cycle progression, and induction of programmed cell death in vivo and in vitro. Resveratrol could block the activation of MAPKs and AP-1 in the skin of mice. Consumption of berries and red fruits rich in polyphenols contributed to the reduction of cancer through a variety of mechanisms.

Polyphenols have also been considered as potential therapeutic agents for altering brain aging processes, and as possible neuroprotective agents in progressive neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases.

Note: Some of the material for this article was gleaned from this interesting scientific study on the subject of polyphenols and their potential health benefits: http://www.mdpi.com/1422-0067/8/9/950/pdf