**Onions: A Source of Flavonoids**

Ana Sofia Rodrigues, Domingos P.F. Almeida,

Jesus Simal-Gándara and

Maria Rosa Pérez-Gregorio

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.69896

#### **Abstract**

Flavonoids are a large and diverse group of polyphenolic compounds with antioxidant effects, and onion (*Allium cepa* L.) is one of the richest sources of dietary flavonoids. Flavonoid content is affected by endogenous factors—genotype and agro-environmental conditions. Considerable research has been directed toward understanding the nature of polyphenols in different products and the factors influencing their accumulation. This review examines the impacts of pre- and postharvest factors on onions' flavonoid content, highlighting how this knowledge may be used to modulate their composition and the potential use of onion by-products.

**Keywords:** polyphenols, plant foods, *Allium cepa*, preharvest factors, harvest handling, genotype
