A note on the volatile secondary metabolites of Foeniculum vulgare Mill. (Apiaceae)

An analysis (GC and GC/MS) of Foeniculum vulgare Mill. (fennel) root and schizocarp essential oils and diethyl ether extracts enabled the identification of 89 different components, representing 98.2-100% of the total samples. One fourth of the identified compounds (24 in total) are reported for the first time as fennel volatiles. The most abundant classes of constituents of all four analyzed samples were the phenylpropanoids (69.5-85.5%) and monoterpenoids (11.7-26.9%). The dominant volatile metabolites of the schizocarps were fenchone (13.3-18.8%) and (E)-anethole (66.1-69.0%). Contrary to that, terpinolene (6.2-6.5%) and dillapiole (71.4-77.5%) were the major volatiles of fennel roots. The most striking differences between the chemical composition of the analyzed oils and their corresponding extracts were a rather surprising presence of a significant relative amount of apiole in the root oil (9.3%; this compound was detected only in trace amounts in the root extract) and the high percentage of 10-nonacosanone in the schizocarp extract (5.8%; this ketone was absent from the schizocarp oil). Possible explanations of the mentioned differences were put forward. The AMS (average mass scan of the total ion chromatogram) profiles/fingerprints of the volatile oils and extracts of F. vulgare roots and fruits are also given in the paper.