Monoterpenoid Indole Alkaloids from Alstonia yunnanensis and Their Cytotoxic and Anti-inflammatory Activities

The 80% ethanol extract of Alstonia yunnanensis afforded five new monoterpenoid indole alkaloids: 11-hydroxy-6,7-epoxy-8-oxo-vincadifformine (1), 14-chloro-15-hydroxy-vincadifformine (2), perakine N-4-oxide (3), raucaffrinoline N-4-oxide (4), and vinorine N-1,N-4-dioxide (5), together with three known compounds: 11-methoxy-6,7-epoxy-8-oxo-vincadifformine (6), vinorine N-4-oxide (7) and vinorine (8). The structures of the isolated compounds were established based on 1D and 2D (H-1-H-1-COSY, HMQC, HMBC, and ROESY) NMR spectroscopy, in addition to high resolution mass spectrometry. The isolated compounds were tested in vitro for cytotoxic potential against seven tumor cell lines and anti-inflammatory activities. Compounds 3, 4 and 7 exhibited weak cytotoxicity against the tested cell lines and selective inhibition of Cox-2 (>85%).