Bioactivity of the extracts and the isolation of lignans from the seeds of Centaurea dealbata

Centaurea dealbata Willd. (Family: Asteraceae) belongs to the big genus Centaurea that comprises ca. 500 species. The n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the seeds of C. dealbata have been assessed for antioxidant activity and general toxicity using, respectively, the DPPH assay, and the brine shrimp lethality assay. Both the DCM and the MeOH extract showed significant levels of antioxidant activities with an RC 50 value 6.8 x 10(-2) and 4.7 x 10(-2) mg/ mL, respectively. None of the extracts exhibited any signifi cant general toxicity (LD50 = > 1000 mg/ mL). Three major bioactive components of the MeOH extract were found to be the lignans, arctigenin, arctiin and matairesinoside. The structures of these lignans were elucidated by comprehensive spectroscopic analyses, and also by direct comparison with the respective published data. This is the first report on the occurrence of arctiin and matairesionl in C. dealbata. The distribution of these lignans within the genus Centaurea has also been presented.