Cytotoxic diterpenoids from the aerial parts of Scoparia dulcis

Two formerly undescribed labdane-type diterpenoids, scoparicols C (1) and D (2), one previously unreported scopadulane-type diterpenoid 1β-hydroxydulcinodal-13-one (3), along with six known biogenetically related analogs (4−9) were separated from the aerial parts of a traditional ethnological herb, Scoparia dulcis. Spectroscopic techniques including MS NMR and ECD were employed to characterize the structures of these molecules. While the oxidation at C-1 in 3 was reported for scopadulane-type diterpenoids for the first time, compound 7 was first obtained as a natural product in the present work. The cytotoxicity of all the isolates against four tumor cell lines (MCF-7, MDA-MB231, Hela and A549) were tested, with selective compounds showing activity in the IC50 range of 4.31–28.6 μM.