STUDIES ON THE FRUITS OF FOENICULUM SPECIES AND THEIR ESSENTIAL OIL

Summary

The species of F. dulce and F. vulgäre as well as selected families and sexual hybrids were studied. Morphological measurements of the fruits and standard analyses of the essential oils were carried out. By means of gas chromatography of the recovered oils (water–steam and steam distillation) and direct gas chromatography of the fruits the following results were obtained:

1. The monoterpene hydrocarbon fraction of the volatile oil contained 18 compounds. There was a remarkable quantitative difference between the hydrocarbons of the two species.

2. The volatile oil of F. dulce had a lower content of fenchon than F. vulgäre. The content of estragol in proportion to that of anethol was relatively constant in the distilled oils of both species.

3. The results of the standard analyses showed that steam distillation yielded more volatile oil with higher content of anethol than water–steam distillation. Water–steam distillation gave approximately the same relative content of estragol as steam distillation. The latter gave usually a higher content of fenchon relative to anethol.

4. The fruits of the selected families from var. dulce were smaller in size than the standard whereas in the families of var. vulgäre they were correspondingly larger. The fruits from the sexual hybrids (vulgäre × dulce) occupied a medium position between the two parent forms.

5. Usually quite a different picture of the proportion anethol : estragol : fenchon is obtained by direct gas chromatography of the fruits than by analysis of the distilled oils. This is probably due to difference in the ripeness of the fruits used for the distillation of the oil. Green fruits of fennel contained relatively more fenchon than brownish ones.

6. The content of fenchon of the selected families was close to the corresponding standards (dulce × vulgäre) with the exception of No. 9 which showed a higher content of fenchon (10.7 %). The sexual hybrids had inherited the lower content of fenchon of the female parent.

7. Direct gas chromatography lends itself very well to selection studies. Only one half of a mericarp is necessary for a total analysis of the volatile oil constituents of fennel.

Zusammenfassung

Das ätherische Öl von Foeniculum dulce, F. vulgäre, der Nachkommenschaft selektierter Pflanzen und der Bastarde zwischen den beiden Arten wurde gas–chromatographisch verglichen.

Es bestehen deutliche quantitative Unterschiede zwischen den 18 vorhandenen Monoterpen–Kohlenwasserstoffen beider Arten. Dabei ist das Verhältnis bestimmter Komponenten zueinander abhängig von der Art der ölgewinnung (Wasser– oder Dampfdestillation). F. dulce besitzt einen geringeren Gehalt an Fenchon als F. vulgäre, während das Verhältnis Estragol zu Anethol in beiden Arten ziemlich konstant ist. Das Verhältnis Anethol : Estragol : Fenchon ist recht unterschiedlich je nach Art der Gewinnung des Öles. Es besteht jedoch die Möglichkeit, daß dafür das verschiedene Alter der für die Destillation und die direkte GC benutzten Früchte verantwortlich ist.

Der Fenchon–Gehalt der Bastarde F. dulce × F. vulgäre ist bedeutend geringer als derjenige von F. vulgäre und nähert sich den Werten von F. dulce. Die Größe der Achänen der Bastarde ist intermediär.