A chemotaxonomic study of endemic species of genus Tanacetum from the Canary Islands. 
Aerial parts of Tanacetum oshanahanii collected at "Jardín Canario Viera y Clavijo", Tanacetum ptarmiciflorum collected at Los Moriscos (Tejeda), and Tanacetum ferulaceum var.  latipinnum collected at Anden Verde (Agaete) in Gran Canaria, Canary Islands, afforded three sesquiterpenes related to nerolidol and six sesquiterpene lactones whose structures were established on the basis of their spectroscopic data and chemical transformations.  In this work we show that this type of sesquiterpene lactones could be used as chemotaxonomic markers.  A series of sesquiterpene lactones described in this paper were assessed for cytotoxicity against HL-60 and U937 cancer cell lines.  The derivatives 106a and 98a displayed cytotoxic properties showing IC50 values between 5 and 11 μM. Furthermore, we demonstrated that these selected sesquiterpene lactones induce apoptotic cell death in human leukemia cells through a mechanism that involves activation of multiple caspases and moreover cell death was found to be associated with the release of cytochrome c.