Triterpenoid acids characterized by the oxidation of the C-27-methy from the roots of Astilbe grandis Stapf ex Wils

Two unprecedented oleane-type triterpenes (5–6) were isolated from the roots of Astilbe grandis Stapf ex Wils, along with four known triterpenes (1–4), all of which were separated from this plant for the first time. The structures of these compounds were elucidated on the basis of spectroscopic analyses especially analysis of 2D NMR data, and the absolute configurations of 5 and 6 were determined by comparison of experimental and calculated ECD data. The structure of 5 was further confirmed by single crystal X-ray diffraction analysis. Compounds 1–6 were evaluated for their in vitro anti-tumor activities on A549, Caco-2, H460 and Skov-3 cells lines. All of the compounds exhibited obvious anti-Caco-2 activity with IC50 values ranging from 1.86 to 4.94 μM, among of them compound 6 also had the apparent effect on A549 cells. In addition, compounds 1, 4 and 5 were evaluated relatively strong inhibitory activity against H460 cells' growth with IC50 values of 5.13 μM, 5.65 μM and 8.85 μM respectively.