Antioxidant treatment and endothelial dysfunction: is it time for flavonoids?

Endothelial dysfunction represents an imbalance between vasodilatory and vasoconstrictory molecules secreted by endothelium. Oxidative stress is a major factor leading to endothelial dysfunction with significant prognostic implications for cardiovascular events. The generation of reactive oxygen species is strongly related to various oxidase enzymes such as xanthine oxidase, uncoupled endothelial nitric oxide synthase, cyclooxygenase, glucose oxidase, lipooxygenase, nicotinamide-adenine dinucleotide phosphate oxidase and to mitochondrial electron transport mechanisms. Several pharmaceutical agents exert effects beyond their principal role, such as anti-inflammatory and antioxidant, while the reports on antioxidant vitamins remain controversial especially those based on large scale studies. Moreover, there are studies on other agents already patented, but these are not well evaluated. Recently, there is growing interest in the role of dietary flavonoids and their potential to improve endothelial function by modifying oxidative stress status. Flavonoids are important components of 'functional foods', with beneficial effects on cardiovascular health, mainly due to their antioxidant activity. However, the vascular-protective role of flavonoids and especially their antioxidant properties are still under investigation.