Four new diterpenoids isolated from the Euphorbia rapulum.

Four new diterpenoids named 1-epi-9-hydroxydepressin (1), 1-epi-8-hydroxydepressin (2), 2,13,9-trihydroxy-labda-8(17),12(E),14-triene (3) and tagalsin I (4) were isolated from Euphorbia rapulum. The structures of these compounds were elucidated by means of various spectroscopic methods. All the isolated compounds were evaluated for cytotoxic activities against HepG2, MCF-7, and C6 cell lines, and compound 4 showed moderate selective activity against MCF-7 cell line with an IC50 value of 31.8 µM.