Characterization of Key Odorants in Cumberland Rosemary, Conradina verticillata

Conradina verticillata Jennison, commonly known as Cumberland Rosemary, is a threatened plant from the mint family Lamiaceae. This species is a flowering, perennial shrub found in only a few counties of Kentucky and Tennessee. Cumberland Rosemary possesses a unique aroma profile; however, the odorants responsible for its aroma have not been previously identified. In this study, a total of 32 odorants were identified in Cumberland Rosemary 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 ≥ [greater than or equal to] 64 were quantitated by stable isotope dilution assays (SIDA), and their odor activity values (OAV) were calculated. Odorants with OAV ≥ [greater than or equal to] 1 included 1-octen-3-one (earthy-mushroom, OAV 2900000), 1,8-cineole (eucalyptus, OAV 510000), borneol (earthy, OAV 10000), bornyl acetate (earthy-fruity, OAV 3700), eugenol (spicy, OAV 2200), menthone (mint, OAV 130), and camphor (herbaceous, OAV 72). Sensory analysis confirmed that an odor simulation model, based on the quantitative data, was a close match to the aroma of the plant. Omission studies determined the key odorants within Cumberland Rosemary’s distinct aroma profile. The stereochemistry of selected odorants was also determined by chiral chromatography. These selected chiral odorants included, α-pinene (70% (R)-(+) to 30% (S)-(−)), 1-octen-3-ol (>99% (R)-(−)), menthone (>99% (2S,5R)-(−)), camphor (>99% (R)-(+)), linalool (97% (R)-(−) to 3% (S)-(+)) borneol (57% (1S,2R,4S)-(−) to 43% (1R,2S,4R)-(+)) and carvone (48% (S)-(+) to 52% (R)-(−)). This study established a foundation for future research on the aroma chemistry of C. verticillata and the other 6 members of the Conradina genus.