The term flavonoid refers to a class of plant secondary metabolites. According to the IUPAC nomenclature, they can be classified into:
Catechin Quercetin Benzopyran Glycoside White tea Gallocatechol Quercitrin Green tea Chromone Vitamin C Hesperidin Tangeritin Flavonols Hesperetin Rutin Flavones Luteolin Proanthocyanidin Kaempferol Epigallocatechin gallate Anthocyanin Cocoa Antioxidant Citrus Glycitein Wine Pyrylium salt Coumaric acid Phytoalexin Chalcone Homoeriodictyol University of Düsseldorf Eriodictyol Phenyl group Phenylpropanoid Apigenin Myricetin Daidzein Naringenin Pelargonidin