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 N4-oxide (3), raucaffrinoline N4-oxide (4), and vinorine N1,N4-dioxide (5), together with three known compounds: 11-methoxy-6,7-epoxy-8-oxo- vincadifformine (6), vinorine N4-oxide (7) and vinorine (8). The structures of the isolated compounds were established based on 1D and 2D (1H-1H-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%).