Three new sesquiterpenoids from the stems of Strophanthus divaricatus

Three new aromadendrane-type sesquiterpenoids (1-3) and five known compounds (4-8) were isolated from the stems of Strophanthus divaricatus. Their structures were determined by spectroscopic methods including HR-ESIMS, 1D and 2D NMR. The absolute configurations of 1-3 was determined by comparison of the experimental and computed ECD spectra. Neridienone A (6) exhibited significant cytotoxicity against human cancer cell lines BEL7402, SGC-7901, K562, A549, and HeLa with IC50 values of 3.30 +/- 0.01, 2.25 +/- 0.01, 2.02 +/- 0.03, 1.55 +/- 0.01, 4.73 +/- 0.07 isM, respectively.