Contribution to the study of Strychnos usambarensis GILG, main ingredient of an African curarizing arrow poison

The thesis is subdivided in four parts and two annexes . the first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of arrow poisons in the World and particularly in Africa; the third part describes the isolation of eight indole alkaoids ( 5 new and 3 known ones) and their structure determination thanks to modern spectroscopic methods.The fourth part is applied to the biosynthesis of these alkaloids and to the identification of loganic acid.The first appendix describes the phytochemical screening of 33 Rwandan plants mainly collected in the National Park of Akagera. The second appendix relates pharmacological experiments on crude fractions and some isolated alkaloids.