Quality evaluation of essential oils from fennel achenes grown in Morocco for industrial use

The fennel plant is an aromatic Apiaceae, widely cultivated in the Mediterranean basin to serve as a vegetable (azoricum variety, bulbous) and condiment (dulce variety, sweet) and for the production of EO rich in (E)-anethole (vulgare variety, bitter). Our previous work has shown that the EOs of the dulce and azoricum varieties contain more limonene and less α-pinene and fenchone compared to the vulgare variety. The latter is a more productive EO than the dulce variety, as it provides more fruit but is less rich in (E)-anethole and limonene and contains a large quantity of bitter-flavored substances such as α-pinene and fenchone.

The aim of our investigations was to formulate standards that must be met before fennel fruit can be marketed.

We carried out a study on the EO composition of 14 batches of cultivated fennel fruits marketed in Morocco. The compounds detected were determined by means of GC-MS and 25 compounds are identified (16 monoterpenes and 9 arylpropenes). We report the unusual presence of sabinene hydrate, p-butylanisole, elemicin, and two isomers, methyleugenol and methylisoeugenol.

Among the 14 batches analyzed, six samples of sweet fennel and just one batch of bulbous fennel were suitable for consumption. The consumer has the right to expect a product with an aniseed taste, with more than 50% (E)-anethole, less than 20% fenchone, and less than 20% (E)-anethole oxidation compounds, under the names "sweet fennel", "bulbous fennel", and "bitter fennel". We propose that fennel containing more than 10% estragole, or highly oxidized arylpropenes (20%) with a less aniseed taste, should be marked fennel rich in estragole or rich in elemicin. This latter molecule is structurally close to mescaline and is psychoactive at high doses. The gradual accumulation of this substance in the body following repeated consumption over a long period leads to serious adverse effects (cumulative toxicity).