Key Odorants of Pycnanthemum incanum and Stereochemistry of Chiral Compounds

Pycnanthemum, a genus in the Lamiaceae family, is comprised of a diverse group of aromatic plants commonly known as wild mountain mint. Due in part to their high terpene content, Pycnanthemum species have broad potential for health-promoting, cosmetic, culinary, and food flavoring applications. However, to fully understand the scope of applications and benefits of the different members of the Pycnanthemum genus a deeper understanding of the chemical composition of the plants is needed. To gain insight into the odorants driving the characteristic aroma of Pycnanthemum spp., a species with a pungent mintlike odor, Pycnanthemum incanum, was selected for comprehensive odorant characterization. Odorants present in P. incanum were identified by coupling solvent assisted flavor evaporation (SAFE) and aroma extract dilution analysis (AEDA), which afforded 24 odorants including 14 odorants with flavor-dilution (FD) factors ≥4. Selected odorants were quantitated by stable isotope dilution assays (SIDAs), and odor-activity values (OAVs) were calculated. The odorants with the highest OAVs included β-ionone (floral, violet; OAV 300), myrcene (terpeny, OAV 120), linalool (floral, citrus; OAV 79), and pulegone (mint, medicinal; OAV 58). In addition, an odor recombination model was developed based on the quantitative data and sensorially compared to the original plant odor. Descriptive analysis confirmed that the sensory attributes of the odor recombination model showed no differences from those of the original P. incanum plant material. Lastly, enantiomeric proportions of chiral odorants in P. incanum were determined by chiral chromatography and the results revealed that the enantiomeric ratios were unique; however, comparable to those reported in other plant species. The characterization of key odorants contributing to the odor of Pycnanthemum incanum provided valuable insight into the chemistry of this underutilized plant and provides a foundation for future studies aimed at the characterization of other species in the Pycnanthemum genus.