Theoretical Study of the Radical Scavenging Potencies of the Metabolites of Quercetin and Kaempferol

A lot of scientific studies support a protective effect of polyphenols on chronic degenerative diseases. Initially this effect was attributed to the radical scavenging properties of these compounds but nowadays a more complex pattern emerges. Concomitantly with the radical scavenging properties, the in vitro effects exhibit a diminution of oxidative stress by other pathways, in particular metal interaction and inhibition of ROS producing enzymes such as xanthine oxidase, NADPH oxidase and lipoxygenase. There is also evidence of processes where polyphenols act as signaling molecules. In this pattern, the interaction decreases the inflammatory response of the bodies and thus, the production of ROS. However the in vivo studies are not simple to analyze and can be in contradiction with the in vitro ones. This is due to the fact that polyphenols are metabolized during their absorption in the body. The active molecules are no more the ingested ones.

It has been established that the dietary intake of polyphenols ranges between 0.15 and 1 g a day. Among the polyphenols, the flavonoids have paid a lot of attention because of its numerous properties. Theconsumption of some of them, generally as glycosylated derivatives, can attain 10-100 mg a day. However their levels rarely exceed 1 mM in human plasma. This is the consequence of a strong and complex catabolism during digestion that has been extensively studied by both in vitro and in vivo experiments.