Antioxidant effect of polyphenols and natural phenols

A polyphenol antioxidant is a hypothetized type of antioxidant, in which each instance would contain a polyphenolic substructure; such instances which have been studied in vitro. Numbering over 4,000 distinct chemical structures (mostly from plants), such polyphenols
may
have antioxidant activity in vitro

(although they are unlikely to be antioxidants in vivo). Hypothetically, they may affect cell to cell signaling, receptor sensitivity, inflammatory enzyme activity or gene regulation, although high quality clinical research has not confirmed any of these possible effects in humans .) and vegetables such as broccoli, cabbage, celery, onion and parsley are rich in polyphenols. Red wine, chocolate, black tea, white tea, green tea, olive oil and many grains are sources.

Consuming dietary polyphenols have been evaluated for biological activity in vitro, but there is no evidence from high quality clinical research that they have effects in vivo. Inflammation such as in coronary artery disease. Other possible effects may result from consumption of foods rich in polyphenols, but are not yet proved scientifically in humans, so are not allowed as health statements by the FDA. Other more detailed chemical research has elucidated the difficulty of isolating individual phenolics. Because significant variation in phenolic content occurs among various brands of tea, there are possible inconsistencies among epidemiological studies implying beneficial health effects of phenolic antioxidants of green tea blends. The Oxygen Radical Absorbance Capacity (ORAC) test is a laboratory indicator of antioxidant potential in foods and dietary supplements. However, ORAC results cannot be confirmed to be physiologically applicable and have been designated as unreliable.

There is debate regarding the total body absorption of dietary intake of polyphenolic compounds. While some indicate potential health effects of certain specific polyphenols, most studies demonstrate low bioavailability and rapid excretion of polyphenols, indicating their potential roles only in small concentrations in vivo. The skin is exposed to various exogenous sources of oxidative stress, including ultraviolet radiation whose spectral components may be responsible for the extrinsic type of skin aging, sometimes termed photoaging. Controlled long term studies on the efficacy of low molecular weight antioxidants in the prevention or treatment of skin aging in humans are absent.

Experiments on linoleic acid subjected to 2,2′ azobis (2 amidinopropane) dihydrochloride induced oxidation with different combinations of phenolics show that binary mixtures can lead to either a synergetic effect or to an antagonistic effect. Antioxidant levels of purified anthocyanin extracts were much higher than expected from anthocyanin content indicating synergistic effect of anthocyanin mixtures.