Characterization of Key Odorants in Cumberland Rosemary, Conradina verticillata

Conradina verticillata Jennison, commonly known as Cumberland Rosemary, is an endangered plant from the mint family Lamiaceae. This species is a flowering, perennial shrub found only in a few counties in Kentucky and Tennessee. Although the odorants responsible for Cumberland Rosemary's unique aroma have not been previously characterized, in this study, a total of 32 odorants were identified using gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Odorant flavor dilution (FD) factors were determined through the application of aroma extract dilution analysis (AEDA). Seven odorants with FD factors ≥64 were quantitated by stable isotope dilution assays (SIDA), and their odor activity values (OAV) were calculated. Odorants with OAV ≥1 included 1-octen-3-one (earthy-mushroom, OAV 2,900,000), 1,8-cineole (eucalyptus, OAV 510,000), borneol (earthy, OAV 10,000), bornyl acetate (earthy-fruity, OAV 3,700), eugenol (spicy, OAV 2,200), menthone (mint, OAV 130), and camphor (herbaceous, OAV 72). Sensory analysis revealed that an odor simulation model based on the quantitative data was a close match to the aroma of the plant. Omission studies determined that 1-octen-3-one, 1,8-cineole, and eugenol were the key odorants critical to Cumberland Rosemary's distinct aroma profile. The stereochemistry of selected odorants was also determined by chiral chromatography. This study established a foundation for future experiments on the aroma chemistry of C. verticillata and the other six members of the Conradina genus.