Studies on the constituents of Cyclanthera pedata fruits:: Isolation and structure elucidation of new flavonoid glycosides and their antioxidant activity

The isolation of six flavon glycosides (1-6), among them four new natural compounds (1-4), from the CHCl3/MeOH extract of the fruits of Cyclanthera pedata is reported. All of the structures were elucidated by spectroscopic methods, including the concerted application of one-dimensional (H-1, H-1 TOCSY, C-13, and C-13 DEPT-NMR) and two-dimensional NMR techniques (DQF-COSY, HSQC, and HMBC). For all of the isolated compounds the antioxidant activity was determined by measuring the free radical scavenging activity, using the Trolox equivalent antioxidant capacity (TEAC) method, and the coupled oxidation of beta -carotene and linoleic acid.