Monoterpenoid indole alkaloids from Alstonia rupestris with cytotoxic, antibacterial and antifungal activities

A chemical investigation of the 80% EtOH extract of the aerial plant of Alstonia rupestris afforded four new monoterpenoid indole alkaloids, 6,7-epoxy-8-oxo-vincadifformine (1), 1 1-acetyl-6,7-epoxy-8-oxo-vincadifformine (2), 11-hydroxy-14-chloro-15-hydroxyvincadifformine (3), and perakine N-1,N-4-dioxide (4), together with two known compounds, 11-hydroxy-6,7-epoxy-8-oxovincadifformine (5) and vinorine N-1,N-4-dioxide (6). Structural elucidation of all the compounds was performed by spectral methods such as 1D- and 2D-NMR, IR, UV, and HRESIMS. Alkaloids 1, 2 and 5' showed significant cytotoxicities against all the tested tumor cell lines of the head and neck squamous cell carcinoma with IC50 value less than 20 mu M and antimicrobial activities against two fungi (Altemaria alternata and Phytophthora capsici). Alkaloids 4 and 6 exhibited the activity against bacterium Staphylococcus aureus. (c) 2014 Published by Elsevier B.V.