From the Manufacturer:
Quercetin (or quercetine) is an important member of a class of naturally occurring plant pigments known as flavonoids. The distinctive red color of some wines, onions and apples is due to the presence of quercetin. The latter two are particularly rich sources of the compound, as are black and green teas. It is also interesting that quercetin serves as a basic building block for many other members of the flavonoids family.
The main claims for quercetin’s health benefits are centered on its powerful antioxidant, anti-histamine, antimicrobial and anti-inflammatory properties.
Along with other antioxidants, quercetin fights the damaging free radical molecules that are a major cause of aging and degenerative disease in modern Western societies. Several population studies have linked a high intake of quercetin and other flavonoids to a reduced risk of certain disorders.