Alliuocide G, a new flavonoid with potent α-amylase inhibitory activity from Allium cepa L.

Chemical investigation of the ethyl acetate fraction of the dried outer scales of Allium cepa L. afforded one new flavonoid named alliuocide G, together with four known compounds.Their structures were unambiguously established on the bases of NMR spectroscopy ( 1 H, 13 C, DEPT, and HMBC) and mass spectrometry.The isolated compounds showed potent α-amylase inhibitory activities, in addition the new compound had antioxidant activity.