A new homoisoflavone from Portulaca oleracea L. and its antioxidant activity.

A new compound was identified as 3-(2-hydroxybenzyl)-5,7-dimethoxy-4H-chromen-4-one (or 2'-dihydroxy-5,7-dimethoxy-homoisoflavone), oleracone F (1), together with p-hydroxy ethyl cinnamate (2) and 4-hydroxy-3-methoxy ethyl cinnamate (3) isolated from the Portulaca oleracea L. for the first time and six known compounds, salicylic acid (4), β-carboline-3-carboxylic acid (5), aurantiamide (6), portulacanone A (7), B (8) and C (9). Their structures were determined using spectroscopic methods, including one- and two-dimensional nuclear magnetic resonance and high-resolution electrospray ionization time-of-flight mass spectrometry. Notably, oleracone F (1) presented scavenging activity in 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical quenching assay, with IC50 value of 17.78 μM.