Isolation and determination of optically pure carvone enantiomers from caraway (Carum carvi L.), dill (Anethum graveolens L.), spearmint (Mentha spicata L.) and Mentha longifolia (L.) Huds.

Abstract
Optically pure (S)‐(+)‐carvone was isolated from the essential oils of the fruits of caraway and dill. Optically pure (R)‐(−)‐carvone was isolated from the essential oils of the leaves of spearmint and Mentha longifolia. Determination of the enantiomeric purity of the natural flavour was performed by 1H‐NMR spectroscopy using a chiral lanthanide shift reagent, Eu(hfc)3.