Quercetin is a pentahydroxyflavone having the five hydroxy groups placed at the 3-, 3'-, 4'-, 5- and 7-positions. It is one of the most abundant flavonoids in edible vegetables, fruit and wine. It has a role as a geroprotector, an antioxidant, an antibacterial agent, an antineoplastic agent, a protein kinase inhibitor, a chelator, a radical scavenger, an Aurora kinase inhibitor, a plant metabolite, a phytoestrogen and an EC 1.10.99.2 [ribosyldihydronicotinamide dehydrogenase (quinone)] inhibitor. It is a pentahydroxyflavone and a 7-hydroxyflavonol. It is a conjugate acid of a quercetin-7-olate.
