Vibsane-type diterpenoids from Viburnum odoratissimum and their cytotoxic activities

Seven new diterpenoids (1-7), including five 7-membered ring vibsane-type diterpenoids, vibsanolide A-E (1-5) and a pair of epimers of 14,15,16,17-tetranorvibsane-type diterpenoids possessing bicyclo[4.2.1]nonane moiety, vibsanolide F-G (6-7), together with twelve known analogues (8-19) were isolated from the crude extracts of the leaves of Viburnum odoratissimum using Small Molecule Accurate Recognition Technology (SMART). These structures including absolute configurations were elucidated by means of comprehensive analyses of spectroscopic data, as well as comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. These compounds were evaluated for their cytotoxic activities against A549 and HepG2 cells by MTT assay. The results showed that compound 2 exhibited potent cytotoxic activity against A549 cells with IC₅₀ value of 1.11 μM. Further staining experiments indicated that 2 could promote apoptosis induction, enhance reactive oxygen species (ROS) level and attenuate mitochondrial membrane potential (MMP) in A549 cells. Taken together, these findings provided new insights into understanding the cytotoxic activity of vibsane-type diterpenoids and it is meaningful to further investigate the application potential of V. odoratissimum.