[Studies on antifertility constituents of Siegesbeckia glabrescens Mak].

Three diterpenes including a new compound were isolated from the whole plant of Siegesbeckia glabrescens Mak. The new one was named as neodarutoside and its structure was elucidated as ent-3 alpha, 15,16-trihydroxy pimarane 3,15-bis-(beta-glucopyranoside) based on the spectral evidence and chemical transformation. The other two were darutigenol and darutoside. Darutoside possesses the activity of termination of early pregnancy in experimental rats at a dosage of 20-40 mg/kg.