Turkish medicinal plants provide a rich source of biologically-active natural products. With the use of simple bioassays, it is possible to evaluate the bioactivity of the natural compounds. Antifungal screening of 16 compounds in a matrix format from two Verbascum species growing in Turkey was conducted directly on thin-layer chromatographic (TLC) plates sprayed with a spore suspension. Compounds possessing strong antifungal activity produced a clear zone of inhibition bounded by a sharp margin regardless of the size of the inhibitory zone. Ilwensisaponin A and C from Verbascum pterocalycinum var. mutense Hub.-Mor. were found to be active. Bioautographic assay indicated that the saponins appeared to be the most effective against Colletotrichum acutatum, C. fragariae and C. gloeosporioides.