Flavonoids and isoflavonoids are natural compounds occurring in different plant species. Dietary intake of such compounds might lead to beneficial or adverse effects in the human body. In this research 18 (iso)flavonoids with a specific decoration (substitution with 5 carbon atoms, i.e. prenylation) were purified and it was observed that these specific decorations could change the hormonal activity towards both human estrogen receptors. The type of decoration was found to be most important for influencing the hormonal activity. However, in some cases the backbone structure itself influenced the hormonal activity as well. Finally, liver metabolism of the compounds was studied and it was found that all compounds were extensively metabolized, which might result in different hormonal activities. All of these findings can be useful for drug developers.