A Novel Flvonol Glucoside from Onion

A new flavonol glucoside was isolated from the outer bulb of onions (Allium cepa).The structure was determined by the analysis of spectral data.Onion (Allium cepa) is well known as a rich source of flavonoid.Hirose et al. have been isolated oxidative quercetin derivatives along with quercetin from outer scale of onions. 1 These compounds structurally very interested.For the purpose of utilization of onion and the isolated compounds, we have studied the constituents of A. cepa, from which we isolated a flavonol glucoside (1) having an oxidative quercetin derivative as aglycone.The MeOH extract of outer scales of onion was repeatedly purified by Silica gel and LH-20 column chromatography to give a new flavonol glucoside along with three known compounds (2, quercetin and quercetin 4'-O-glucoside).Compound (1) was isolated as a yellow amorphous solid, and gave positive reactions to the FeCl 3 and Gibbs tests on TLC.In the negative ion FABMS spectrum, the [M-H] -was observed at m/z 763.1143 which correspond to C 36 H 27 O 19 .The UV spectrum