Method for attaining fennel (Foeniculum vulgare Mill.) seed oil fractions with different composition and antioxidant capacity

Authors: BURKHARDT, ANDREW - University Of Wyoming; SINTIM, HENRY - University Of Wyoming; GAWDE, ARCHANA - University Of Wyoming; Cantrell, Charles; ASTATKIE, TESSEMA - Dalhousie University; ZHELJAZKOV, VALTCHO - University Of Wyoming; SCHLEGEL, VICKI - University Of Nebraska

Submitted to: Journal of Applied Research on Medicinal and Aromatic Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2015
Publication Date: 5/21/2015
Citation: Burkhardt, A., Sintim, H., Gawde, A., Cantrell, C.L., Astatkie, T., Zheljazkov, V.D., Schlegel, V. 2015. Method for attaining fennel (Foeniculum vulgare Mill.) seed oil fractions with different composition and antioxidant capacity. Journal of Applied Research on Medicinal and Aromatic Plants. 2:87-91.

Interpretive Summary: Fennel, a native of the Mediterranean, is widely used in a multitude of applications. It is often used as a herb for cooking and preserving food and has even been researched for its antioxidant protectant qualities for preserving boar semen. It has antimicrobial and carminative properties among other documented uses. Fennel is cultivated for its seeds and foliage, which contain essential oil. The duration of distillation of essential oils changes depending on the plant species. We hypothesized that the collection of fennel seed oil at different time points during the distillation process may result in fennel oil with distinct composition and bioactivity. The major oil component was estragole, which accounted for over 75% of the total essential oil content. Oil with highest estragole content should be obtained by collecting the oil fraction that elutes between 30 and 45 min. If fennel seed oil with high content of trans-anethole is desirable, then the oil distilled in the first 45 minutes should be removed and the remaining oil fraction collected. This study demonstrates an effective method to obtain fennel seed oil fractions of various composition.

Technical Abstract: Fennel (Foeniculum vulgare Mill.) is cultivated for its seeds and foliage, which contain essential oil. We hypothesized that the collection of fennel seed oil at different time points during the distillation process may result in fennel oil with distinct composition and bioactivity. We collected essential oil from fennel seed at ten different distillation times, DT (at 2, 7, 15, 30, 45, 75, 105, 135, 165, and 195 min). Estragole (42.8-84.4% of the total oil) was the main constituent throughout the distillation. (-)-alpha-pinene (0.84%-0.12%) and (R)-(+)-limonene (33.5%-6.3%) were relatively high at initial DT and dropped significantly after the first DT. (-)-fenchone (4.1%-0.5%) showed a near linear decrease until approximately the 165 min DT. If high (-)-a-pinene and (R)-(+)-limonene oil is desirable, then the oil fraction needs to be captured early in the distillation, at 2 min. Oil with highest estragole concentration may be obtained by collecting the oil eluted between 30 and 45 min. DT had an effect on the oil antioxidant activity; the oil from the control (195 minutes distillation time) had the highest antioxidant capacity (481 µmole Trolox equivalents/g), whereas the oil sampled at 45 min DT had the lowest capacity (148 µmole Trolox equivalents/g). This study demonstrated an effective method for obtaining fennel seed oil with differential composition and antioxidant capacity.