| Section2 = }} Quercetin is a flavonoid and, to be more specific, a flavonol. Chemical structure It is the aglycone form of a number of other flavonoid glycosides, such as rutin and quercitrin, found in citrus fruit & onions. Quercetin forms the glycosides quercitrin and rutin together with rhamnose and rutinose, respectively. Medicinal properties Quercetin is found to be the most active of the flavonoids in studies, and many medicinal plants owe much of their activity to their high quercetin… (More on Quercetin)