Enantiomeric composition of limonene and carvone in seeds of dill and caraway grown in Poland.

The enantiomeric composition of limonene and carvone in dill and caraway seeds oils was determined by the chiral gas chromatography. Two different gas chromatography chiral columns were used to obtain enantiomeric separation of both aroma compounds. Nine varieties of dill and two varieties of caraway were investigated. Both enantiomers of limonene and carvone were detected; R(+)-limonene and S(+)-carvone were predominant. The concentration of total limonene and carvone varied among the dill varieties ranging from 5.63 to 18.79 mg/g of seeds and from 8.97 to 18.35 mg/g, respectively. Caraway seeds contain a higher amount of essential oil and consequently higher concentration of limonene and carvone per gram of seeds. In Plewicki variety, the concentration of limonene amounted to 31.41 mg/g of seeds while that of carvone to 36.24 mg/g, in Konczewicki variety it was 17.60 and 22.46 mg/g, respectively. Independently from the variation, the enantiomeric ratio was stable for both compounds in the analyzed samples. The ratio, expressed in percentage of plus optical form to total, showed a very high optical purity of R(+)-limonene (99.1-99.5%), and S(+)-carvone (99.4-99.8%) in both caraway and dill seeds oils.