[Molecular modelling of usambarensine, tubulosine and emetine, cytotoxic amebicide alkaloids]

The analyses of the different possible conformations of usambarensine, tubulosine and emetine, which possess interesting cytotoxic and amoebicide properties showed us that they cannot take the planar conformation proposed to explain the activity of this type of molecules on protein synthesis. Nevertheless, a common (non planar) conformation exists where the angles between the two plans containing the aromatic rings are nearly the same for the three compounds. This fact could confirm the hypothesis of a common receptor which would be slightly different in amoebae because of its higher sensitivity to usambarensine.

Effects of strychnopentamine on cells cultured in vitro

This paper describes the powerful cytotoxic action exerted by strychnopentamine (SP), a dimeric indole alkaloid extracted from Strychnos usambarensis Gilg, on B16 melanoma cells and on non-cancer human fibroblasts cultured in vitro. SP strongly inhibits cell proliferation and induces cell death at a relatively low concentration (less than 1 microgram/ml) after 72 h of treatment in the two lines. Incorporation of [3H]thymidine and [3H]leucine by B16 cells significantly decreases after only 1 h of treatment at 0.5 microgram/ml. SP induces the formation of dense lamellar bodies and vacuolization in the cytoplasm, intense blebbing at the cell surface and various cytological alterations leading to cell death.