Essential oil content and composition in commercially available dill cultivars in comparison to caraway

In field tests carried out over several years, 26 accessions of dill were compared to four annual and seven biennial caraway varieties concerning seed harvest yield, essential oil content and composition. Essential oil contents and carvone ratio in the essential oil are similar in caraway and dill, so harvest yield figures are crucial whether dill can be regarded as an alternative carvone source or not. Dill seed yields were low, 400-600 kg/ha in one year and 200 kg/ha and less in the other year due to seed shattering, compared to 900 kg/ha in biennial caraway, and 1250 kg/ha in annual caraway. Essential oil content was 3.4-4% with dill, 2.8-3.3% in annual and 3.9-5% in biennial caraway. In dill, the carvone content in the seeds was largely independent of the essential oil content, approximately 11 mg/g seeds, whereas different oil contents were due to varying limonene amounts. Minor essential oil components were observed in a proportion of 2% in biennial caraway, 3.5% in annual caraway and 7% in dill. In caraway, cis- and trans-dihydrocarvone and some isomers of carveol and dihydrocarveol were present in the range 0.5-1% each, whereas in dill, cis-dihydrocarvone (3%) and alpha -phellandrene (2%) were most abundant. Apiole and myristicin were absent in most samples, but were found in proportions of 0.2-11% in dill chemotypes where they were present. Solvent extraction of the crushed seeds with hexane, a method using triple extraction and ultrasonic treatment, led to nearly identical results as hydro distillation with dill, but to carvone values 16% lower with caraway. (C) 2001 Elsevier Science B.V. All rights reserved.