Enantiomeric composition of carvone, limonene, and carveols in seeds of dill and annual and biennial caraway varieties

The enantiomeric compositions of limonene, carvone, and carveols were determined in hydrodistillates and hexane extracts of seeds of dill and annual and biennial caraway. A range of varieties and accessions of several harvest years was investigated to gain insight into genetic variation and differences between years. Both enantiomers of limonene, carvone, and cis- and trans-carveol were detected in the two caraway types and, except for (-)-cis-carveol, also in dill. The enantiomeric compositions of the two caraway types were similar, but dill had a higher (-)/total limonene ratio than either caraway type. Due to less complete extraction, the calculated seed contents of all compounds and their enantiomers were lower for hydrodistilled than for hexane-extracted seeds except for (-)-carvone content, which was significantly higher for hydrodistilled seeds, possibly as a result of conversions during extraction. Also, monoterpene composition was altered by hydrodistillation: the more polar carvone was extracted more efficiently than the apolar limonene. Total monoterpene content in biennial caraway was higher than in the two annual species. The contents of all carveol isomers and (-)/total limonene and (-)/total carvone ratios decreased with storage time between harvest and analysis. The correlations between enantiomers of limonene and carvene and the implications for the pathways of limonene and carvene formation in dill and caraway are discussed. As the enantiomeric composition of carvene is similar for dill and annual and biennial caraway, all three are equally suited as carvene suppliers for sprouting inhibition in potatoes.