Odor distinctiveness between enantiomers of linalool: Difference in perception and responses elicited by sensory test and forehead surface potential wave measurement

The effects on humans of inhalation of optically active linalools were examined in terms of sensory tests and portable forehead surface electroencephalographic (IBVA-EEG) measurements in order to assess their odor distinctiveness by chiral isomers. (R)-(-)-Linalools with specific rotation of [alpha](D) = -15.1 degrees were isolated by repeated flash column chromatography from lavender oil, while (S)-(+)-linalools with [alpha](D) = +17.4 degrees and (RS)-(+/-)-linalools with [alpha](D) = 0 degrees and content of (R)-form 50.9% and (S)-form 49.1% were obtained from coriander oil and commercial linalool, respectively, by using the same method. With the use of an inhalator, each was administered to subjects both before and after 10 min of work. It was found that administration after work evoked different subjective impressions when compared with that before work depending on the configuration of the isomers and the type of work employed. For instance, inhalation of (R)-(-)-linalool after hearing environmental sounds not only produced a much more favorable impression in the sensory test but was also accompanied by a greater decrease in beta waves after work in comparison with that before work. This is in contrast to the case of mental work, which resulted in a tendency for agitation accompanied by an increase in beta waves. These findings led us to conclude that enantiomeric stereospecificity of linalool evoked different odor perception and responses not only with chiral dependence but also with task dependence. In addition, in comparing these sensory profiling features and IBVA-EEG tendencies between hearing environmental sound and mental work, a tendency was observed for (R)-(-)-linalool to coincide with (RS)-(+/-)-linalool but not with (S)-(+)-linalool.