Dudai, N., Aromatic Medicinal/Spice Crops, ARO, Newe Ya'ar Research Center, PO Box 1021, Ramat Yishay 30095, Israel
Larkov, O., Aromatic Medicinal/Spice Crops, ARO, Newe Ya'ar Research Center, PO Box 1021, Ramat Yishay 30095, Israel
Chaimovitsh, D., Aromatic Medicinal/Spice Crops, ARO, Newe Ya'ar Research Center, PO Box 1021, Ramat Yishay 30095, Israel
Lewinsohn, E., Aromatic Medicinal/Spice Crops, ARO, Newe Ya'ar Research Center, PO Box 1021, Ramat Yishay 30095, Israel
Freiman, L., Aromatic Medicinal/Spice Crops, ARO, Newe Ya'ar Research Center, PO Box 1021, Ramat Yishay 30095, Israel
Ravid, U., Aromatic Medicinal/Spice Crops, ARO, Newe Ya'ar Research Center, PO Box 1021, Ramat Yishay 30095, Israel

The essential oils of five selected clones of Origanum dayi Post were obtained using two techniques, hydrodistillation and tert-butyl methyl ether extraction. Hydrodistillation of the whole plant yielded essential oil amounting to 2.4-2.8% of the fresh weight. A total of 50 volatile constituents of the oil were identified, of which the major ones were 1,8-cineole, α-terpineol, (E)-sabinene hydrate, (E)-sabinene hydrate acetate, terpinen-4-ol and linalyl acetate. The composition of the volatiles obtained by hydrodistillation and by extraction differed mainly in the higher contents of terpinen-4-ol (5.7-14.5%) and α-terpineol (18.3-25.8%) in the distilled oil than in the extract (1.9-4.0% and 10.5-16.8%, respectively), but the former had less (E)-sabinene hydrate acetate (traces-0.2%) than the latter (6.3-13.8%). Extraction of young and old leaves, young and old stems, bracts, calices and corollas revealed differences among the various plant parts in their volatile contents and compositions. Copyright © 2003 John Wiley & Sons, Ltd.