Morphogenetic, Ontogenetic and Diurnal Variability in Content And Constituents of Bitter Fennel (Foeniculum vulgare Miller var. vulgare) Essential Oil

The objective of this study was to determine morphogenetic, ontogenetic and diurnal variability in content and constituents of bitter fennel essential oil. Essential oils of various plant organs (leaf, root-bulb-stalk, flower and seed) of bitter fennel harvested at pre-, full-and post-flowering stages at different times (9 am, 1 and 5pm) were extracted by hydro distillation and analyzed by gas chromatography and mass spectrometry. Essential oil content differed significantly based on plant organ and growing stage, increasing in the order of leaf < flower <seed, with a nearly seven-fold increase occurring in seed essential oil as compared to that of leaf. Essential oil content increased from 1.68% at pre-flowering to 2.18% at full-flowering but decreased sharply to 0.81% at post-flowering. Trans-anethole was found to be the most prominent compound in all esssential oils, with decreasing order of seed > flower > root-bulb-stalk > leaf essential oil. Alpha-pinene, alpha-phellandrene, limonene and fenchone were the other major components, varying significantly with plant growth stages and organs. The present study reveals that the content and constituents of essential oil of bitter fennel from Turkey are predominantly dependent on ontogenetical phase and plant organ.