Associative evidence from observational and intervention studies in human subjects shows that a diet including plant foods (particularly fruit and vegetables rich in antioxidants) conveys health benefits. There is no evidence that any particular nutrient or class of bioactive substances makes a special contribution to these benefits. Flavonoids occur naturally in fruits, vegetables and beverages such as tea and wine. Quercetin is the major flavonoid which belongs to the class called flavonols. Quercetin is found in many common foods including apples, tea, onions, nuts, berries, cauliflower, cabbage and many other foods. Quercetin provides many health promoting benefits, including improvement of cardiovascular health, eye diseases, allergic disorders, arthritis, reducing risk for cancers and many more. The main aim of this review is to obtain a further understanding of the reported beneficial health effects of Quercetin, its pharmacological effects, clinical application and also to evaluate its safety.

Cardiovascular disease constitutes a major public health concern in industrialized nations. Over recent decades, a large body of evidence has accumulated indicating that oxidative stress induced free radicals play a critical role in cellular processes implicated in atherosclerosis and many other heart diseases. However a diet high in antioxidants is associated with a reduced risk of cardiovascular disease. The compound quercetin is a dietary antioxidant with a polyphenolic structure that is present in many foods, such as onion, apples, wine and tea. An increased intake of quercetin has been correlated with a decrease in the risk of cardiovascular diseases. Quercetin has been reported to exhibit a wide range of biological and pharmacological effects in animals and man besides its antioxidative and free radical scavenging actions. This paper reviews various steps of oxidative stress mediated atherogenesis and their signaling pathways and also emphasizes the role of quercetin in controlling oxidative stress and reducing the incidence of cardiovascular diseases.