Comparison of the Essential Oil Content, Constituents and Antioxidant Activity from Different Plant Parts during Development Stages of Wild Fennel (Foeniculum vulgare Mill.)

Abstract

The study was conducted to determine fennel essential oil (FEO) yield, composition, and antioxidant activity during four different maturation stages of umbels with seeds (1st stage: immature-pasty; 2nd stage: premature-waxy; 3rd stage: mature-fully ripe; and 4th stage: seeds only), and leaves of wild fennel (Foeniculum vulgare Mill. subsp. vulgare) from the Montenegro coast. The maximum oil yield was found in premature umbels at the waxy stage (4.76 mL/100 g p.m.) and in fully ripe umbels in the early fruiting stage (5.16 mL/100 g p.m.). Fully ripe seeds contained the lowest FEO (mL/100 g p.m.). The minimum FEO content was found in leaves (0.67%). (E)-anethole (64%), α-phellandrene (11.0%), and fenchone (4.8%) were found to be the main components of the essential oil from immature fennel umbels. (E)-anethole (72.3%), fenchone (9.6%) and methyl chavicol (9.5%) were found to be the main components of the essential oil from premature fennel umbels. (E)-anethole (71.6%), fenchone (10.7%) and methyl chavicol (10.3%) were found to be the main components of the essential oil from mature fully ripe fennel umbels. Fennel seeds were rich in (E)-anethole (75.5%) and fenchone (13.7%). FEO from fennel leaves contained (E)-anethole (32.5%), α-phellandrene (18.8%), p-cymene (17.3%), and β-phellandrene (10.3%) as the main compounds. The antioxidant activity of FEO decreases from leaves (12.37 mg/mL) to seeds (37.20 mg/mL). The degree of DPPH radical neutralization increased with the incubation time. Fennel umbels can be harvested before the fully ripe stage, i.e., at the waxy stage, which considerably reduces seed shedding and losses and increases the essential oil yield.