FLAVONOIDS FROM RED ONION (ALLIUM-CEPA)

Quercetin 3,7,4'-O-beta-triglucopyranoside together with quercetin, qu ercetin 4'-O-beta-glucopyranoside and quercetin 3,4'-O-beta-diglucopyr anoside were isolated from the pigmented scales of Allium cepa var. 'R ed Baron'. The former flavonol has previously been reported to be form ed when cell cultures of a Vitis hybrid is fed with quercetin. Minor a mount of taxifolin 4'-O-beta-glucopyranoside, a rare dihydroflavonol, was also detected. The structures were established on the basis of aci d hydrolysis, chromatography (TLC and HPLC) and home-and heteronuclear NMR spectroscopic techniques. (C) 1997 Published by Elsevier Science Ltd.