Americanin, a bioactive dibenzylbutyrolactone lignan, from the seeds of Centaurea americana.

The reversed-phase preparative HPLC analysis of the methanol (MeOH) extract of the seeds of Centaurea americana afforded a dibenzylbutyrolactone lignan, 3''-O-caffeoyl arctiin (named americanin), together with five known lignans, arctiin, arctigenin, matairesinol, matairesinoside and lappaol A, and two known phytoecdysteroids, 20-hydroxyecdysone and makisterone A. While the structures of the known compounds were determined by direct comparison of the spectral data with published data, the structure of americanin was elucidated by UV, MS and a combination of 1D and 2D NMR spectral analyses. The antioxidant properties and toxicity of the extracts and the isolated compounds were determined by the DPPH and the brine shrimp lethality assays, respectively.