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Book/Book Chapter 
Quercetin: Natural sources and health benefits 
Gã³Mez-Serranillos, MP; Palomino, OM 
Nova Science Publishers, Inc. 
Quercetin: Dietary Sources, Functions and Health Benefits 
Flavonoids are a large group of plant metabolites that are commonly present in fruits, vegetables, cereals and beverages, where they contribute to the bitterness, astrigency, colour, flavour, odour and antioxidant stability of the plant. Epidemiological data suggest that long term consumption of diets rich in flavonoids could provide some health benefits such as lowering arterial pressure, decreasing plasma concentration of lipids and buffering plasma glucose, together with some protection against the development of certain cancers or cardiovascular diseases. Among them, quercetin that belongs to the flavonols components is being investigated for its widespread health benefits. The plant source of quercetin is relatively inexpensive to grow and harvest, and its purification is straightforward. Quercetin is abundant in onion and has been related to diminished mortality from coronary heart disease; it has also shown to exert anticancer properties against benzo(a) pyrene induced lung carcinogenesis in mice and possesses virucidal activity against enveloped viruses such as herpes, simplex type I or parainfluenza type 3. Most of the beneficial effects of quercetin are related to its free radical scavenging activity that supports its antioxidant capability. The antioxidant nature of quercetin is defined mainly by the presence of a catechol group in the B-ring capable of readily donating hydrogen (electron) to stabilise a radical specie. Other features important for the antioxidant nature include the presence of 2,3 unsaturation in conjugation with a 4-oxo-function in the C-ring. In addition, quercetin has proved to be effective and safe for humans at low dosages (500-1000 mg/day). Thus, available data leads to consider the possible relevance of quercetin benefits on various chronic diseases like cardiovascular, metabolic and neurodegenerative diseases associated with oxidative stress. © 2012 Nova Science Publishers, Inc. All rights reserved.