Antioxidant lignans from the seeds of Vitex negundo var. cannabifolia.

A new phenyldihydronaphthalene-type lignan, vitexdoin F (1), along with 22 known lignan derivatives (2-23) was isolated from the seeds of Vitex negundo var. cannabifolia. Their structures were established by comprehensive 1D and 2D NMR spectroscopic analyses. The antioxidant activities of these lignans were evaluated through 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assays, and 16 of these isolates exhibited obvious radical-scavenging effect on the stable-free radical, DPPH.