Fig. 2.

Chemical structures of flavonoids. (A) Basic chemical structures. (B) Buckwheat flavones. Apigenin is an aglycone of vitexin and isovitexin; luteolin is an aglycone of orientin and isoorientin. However, both apigenin and luteolins themselves are not contained in buckwheat (the box with the dashed line suggests). (C) Representative flavonols and a flavonol glycoside, rutin. (D) Representative anthocyanidins. Buckwheat has only cyanidin 3-glycosides. (E) Catechins and epicatechins. Buckwheat, like most other plant species, has only (+)-catechin and (–)-epicatechin.