17-O-Acetyl, 10-hydroxycorynantheol, a Selective Antiplasmodial Alkaloid Isolated from Strychnos usambarensis Leaves

In the course of our investigations on Strychnos usambarensis leaves in order to isolate isostrychnopentamine, the main alkaloid responsible for the antiplasmodial activity of the plant, a new tertiary indolic alkaloid has been isolated: 17-O-acetyl, 10-hydroxycorynantheol 1. Its structure was determined by means of spectroscopic and spectrometric methods such as UV, IR, CD, NMR, and ESI-MS. 17-O-acetyl, 10-hydroxycorynantheol 1 is one of the most active monomeric indole alkaloids known to date showing an in vitro activity against Plasmodium falciparum close to 5 mu M and a high selectivity.