Tagetones A and B, new cytotoxic monocyclic diterpenoids from flowers of Tagetes minuta

Tagetones A (1) and B (2), two new monocyclic diterpenoids were isolated from the n-hexane fraction of fresh flowers of Tagetes minuta L. (Asteraceae). Their structures were established by multiple spectroscopic methods (IR, HR-ESI-MS, and 1D-, and 2D-NMR), in addition to comparison with literature data. Compound 1 showed cytotoxic activity towards MCF7 and A549 cancer cells with IC50 values being 4.68 and 4.24 µmol·L−1, respectively, compared to doxorubicin (IC50 0.13 and 1.12 µmol·L−1, respectively). Compound 2 also exhibited significant activity against HCT116 cancer cells (IC50, 6.30 µmol·L−1).