With the aim of improving the cytotoxic and vascular disrupting activities of flavonoids, several classes of ferrocenyl-modified flavonoids were prepared and tested on cancer and endothelial cells. Three tenmember series of ferrocenyl flavonoids: chalcones ((E)-1-(R-2'-hydroxypheny1)-3-ferrocenylprop-2-en-1-ones), aurones ((Z)-R-2-(ferrocenylidene)benzofuran-3-ones) and flavones (R-2-ferrocenyl-chromen-4-ones) were synthesized by recently reported methods. Three ferrocenyl flavonols (R-3-hydroxy2-ferrocenyl-chromen-4-ones) and four ferrocenyl flavanones (3-ferrocenylmethylidenyl-R-2-phenyl-chroman-4-ones) were also obtained. All compounds were evaluated for their cytotoxic effects on a cancer cell line (B16 murine melanoma) and for their morphological effects on endothelial cells (EAhy 926). Some interesting structure-activity relationships were disclosed: of all the compounds, the halogen-substituted aurones showed the best cytotoxic activity, with IC50 values ranging between 12 and 18 mu M. Ferrocenyl flavonols and ferrocenyl flavanones with substitution in the 3-position (-OH and =C-Fc respectively) were not active against cancer or endothelial cells. Some of the ferrocenyl flavones caused the endothelial cells to adopt a round shape (''rounding up'') at submicromolar concentrations, which can be predictive of vascular disrupting activity. The most morphologically active flavones showed only moderate cytotoxicity against cancer cells, indicating that they may primarily act as antivascular agents. (C) 2013 Elsevier B.V. All rights reserved.