The potential cytotoxic activities of 46 alkaloids isolated from different Strychnos species were tested on different cancer or normal cells cultured in vitro. The authors used a relatively simple microtest which gives good reproducibility. Most of the active compounds belong to the usambarane skeleton but other structure-activity relationships are being discussed.
Quetin-Leclercq, J., De Pauw-Gillet, M.-C., Bassleer, R., & Angenot, L. (1986). Screening of cytotoxic activities of Strychnos alkaloids (methods and results). Journal of Ethnopharmacology, 15(3), 305-316. https://doi.org/10.1016/0378-8741(86)90169-8 (Original work published 1986)