Dimeric progestins from rhizomes of Ligusticum chuanxiong

(3Z′)-(3a′R,6′R,3R,6R,7R)-3,8-dihydro-6.6′,7.3a′-diligustilide was isolated from rhizomes of the “utero-tonic” Chinese medicinal plant Ligusticum chuanxiong. This dimeric phthalide strongly (EC50 ∼ 90 nM) and specifically activated the progesterone receptor.