Four lignans from Portulaca oleracea L. and its antioxidant activities.

A new lignan, named oleralignan (1) and three known componds (+)-syringaresinol (2), (+)-lirioresinol A (3) and monomethyl 3,3',4,4'-tetrahydroxy-δ-truxinate (4) were isolated from the P. oleracea for the first time. The compound (1) were identified by 1D, 2D NMR spectroscopic methods and high resolution electrospray ionization time-of-flight mass spectrometry. In addition, it was found that the four lignans presented the scavenging activities in 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical quenching assay more than that of hydroxyl anisole (BHA). [Figure: see text].