Cytotoxic ent -abietane diterpenoids from the leaves of Croton crassifolius

Two new ent-abietane diterpenoids, 2β,15-dihydroxy-ent-abieta-7,13-dien-3-one (1) and 6β,13α-dihydroxy-ent-abieta-8(14)-en-3-one (2), together a known ent-abietane diterpenoid 3α,7β-dihydroxy-ent-abieta-8,11,13-triene (3), were isolated from the 80% acetone extract of the leaves of Croton crassifolius. The structures of the new compounds were elucidated by spectral methods such as 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy, as well as high resolution mass spectrometry. The isolated compounds were tested in vitro for cytotoxic activity against five urologic carcinoma cell lines. Consequently, compound 3 exhibited some cytotoxicities against all the tested tumor cell lines with IC50 value less than 20.0 μM.