Antioxidative flavonoid glycosides from quinoa seeds (Chenopodium quinoa Willd)

Abstract

Six flavonol glycosides have been isolated from quinoa seeds (Chenopodium quinoa Willd) via normal phase and reverse phase column chromatography. On the basis of spectral data, their structures were established as kaempferol 3-O-[β-D-apiofuranosyl(1‴-2″)]-β-D-galactopyranoside (1), kaempferol 3-O-[α-L-rhamnopyranosyl(1′‴-2″)]-β-D- galactopyranoside (2), kaempferol 3-O-[β-D-apiofuranosyl(1‴-2″)-α-L- rhamnopyranosyl(1′‴-6″)]-β-D-galactopyranoside (3), kaempferol 3-O-(2,6-di-α-L-rhamnopyranosyl)-β-D-galactopyranoside (4), quercetin 3-O-[β-D-apiofuranosyl (1‴-2″)-α-L-rhamnopyranosyl(1′‴-6″)]- β-D-galactopyranoside (5) and quercetin 3-O-(2,6-di-α-L-rhamnopyranosyl)-β-D-galactopyranoside (6). Among them, compounds 1, 4 and 6 were the main flavonoid glycosides found in quinoa seeds and compounds 2, 5, and 6 were isolated from this plant for the first time. All six compounds exhibited antioxidant activity in DPPH test, and two quercetin 3-glycosides showed much stronger activity than the four kaempferol 3-glycosides present.