Antioxidant effect of flavonoids.

Our body generates hydroxyl radicals under a number of conditions. This radical is very unstable and, therefore, very reactive. After attack of radicals on membranes and lipoproteins, lipid peroxidation starts, and may lead to the development of vascular lesions. The human body has developed antioxidant defenses to protect against free radicals such as superoxide dismutases, glutathione peroxidases, plasma iron binding proteins, or alpha tocopherol. Oxidized LDL are believed to play a key role in vascular damage and can modulate several endothelial properties including NO production and expression of adhesion molecules. Antioxidants, such as flavonoids, inhibit "in vitro" oxidation of LDL and their cytotoxicity; in humans consumption of flavonoids appears to be related to a reduction of the risk of cardiovascular diseases. The biochemical mechanisms responsible for this effect remain to be addressed.