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

• A hydrodistillation study with crushed fennel seed was conducted.
• Estragole was the main constituent throughout the distillation.
• (−)-α-Pinene and (R)-(+)-limonene were relatively high at initial distillation time.
• Distillation time affected the oil antioxidant activity.
• We developed a method for obtaining fennel seed oil fractions varying in chemical composition.

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. (−)-α-Pinene (0.12–0.84%) and (R)-(+)-limonene (6.3–33.5%) were relatively high at initial DT and dropped significantly after the first DT. (−)-Fenchone (0.5–4.1%) showed a near linear decrease until approximately the 165 min DT. If high (−)-α-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 min distillation time) had the highest antioxidant capacity (481 μmol Trolox equivalents/g), whereas the oil fraction sampled at 45 min DT had the lowest capacity (148 μmol Trolox equivalents/g). This study demonstrated an effective method for obtaining fennel seed oil fractions with differential composition and antioxidant capacity.

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