Effect of Harvest Years on Chemical Composition of Essential Oil of Bitter Fennel (Foeniculum Vulgare Subsp. Piperitum) Leaves

Essential oil contents on a dry weight basis of ripe fruits of bitter fennel collected in different years were 5.1%, 4.8%, 4.6%, 7.0%, 6.5%, 4.7%, 3.8% and 4.0%, respectively. By GC and GC-MS analysis, the main identified components representing 99.59%, 94.74%, 99.62%, 99.35%, 99.63%, 99.58%, 98.07% and 99.68% of the oils were limonene (3.87–17.63%), fenchone (13.82% to 29.17%) and estragole (25.14% to 65.45%). But, transanethole contents of fruit harvested in 2006 was found very high (44.60%) when compared with oil components of other years. At the same time, a-phellandrene contents of samples harvested in 2005 and 2008 years were found higher than the results of other years. As a result, the chemical composition of oils showed differences according to harvest years.