Catechins as Antioxidants from Buckwheat (Fagopyrum esculentum Moench) Groats

Four catechins and rutin were isolated from ethanol extracts of buckwheat (Fagopyrum esculentum Moench) groats by Sephadex LH-20 column chromatography and preparative HPLC with monitoring of the peroxyl radical scavenging activity. The antioxidant activity of these catechins was higher than that of rutin. The structures of these catechins were established as (−)-epicatechin, (+)-catechin 7-O-β-d-glucopyranoside, (−)-epicatechin 3-O-p-hydroxybenzoate, and (−)-epicatechin 3-O-(3,4-di-O-methyl)gallate on the basis of 1H, 13C, and two-dimensional nuclear magnetic resonance techniques and fast atom bombardment mass spectrometry. The yields of these antioxidant compounds suggest that they are abundant, as is rutin, which is known as a biological phytochemical in buckwheat groats. Keywords: Fagopyrum esculentum; antioxidant activity; flavonoids; (−)-epicatechin; (+)-catechin 7-O-β-d-glucopyranoside; (−)-epicatechin 3-O-p-hydroxybenzoate; (−)-epicatechin 3-O-(3,4-di-O-methyl)gallate