The harmful effects of linear furocoumarins have been demonstrated in several studies. The most typical toxic activity of these compounds is phototoxicity, however, hepatotoxic and carcinogenic effects have also been reported in animal experiments. Three furocoumarins – bergapten, imperatorin and psoralen – were previously described in fennel (Foeniculum vulgare Mill.), a widely used medicinal plant and spice, however no reliable quantitative data are available on the occurrence of these compounds in the fruits of the plant.
The aim of our work was to develop a highly selective and sensitive method for the determination of furocoumarins from fennel and to quantify these substances in several samples of different origin representing a wide range of genotypes. The bergapten, imperatorin and psoralen content of 33 fennel samples was analyzed using an LC-MS method. The measured quantities were compared to the safety recommendations of scientific guidelines in order to assess whether the furocoumarin content of fennel should be considered as a potential risk to the human organism in case of therapeutic application. The furocoumarin content of the fruits if applied at the highest therapeutic dose described in the monograph of the European Medicines Agency  ranged between 0.01-1.22 μg which is below the most restrictive recommendations . Based on this finding, the therapeutic use of fennel could be considered as safe at least based on its low furocoumarin content.
 EMEA/HMPC Foeniculum vulgare subsp. vulgare var. dulce (Miller) Thellung, fructus fennel fruit, sweet EMA/HMPC/411665/2008
 EMEA/HMPC Reflection paper on the risks associated with furocoumarins contained in preparations of Angelica archangelica L. EMEA/HMPC/317913/2006