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 exam ined in terms of sensory tests and portable forehead surface electroencepha lographic (IBVA-EEG) measurements in order to assess their odor distinctive ness by chiral isomers. (R)-(-)-Linalools with specific rotation of [alpha] (D) = -15.1 degrees were isolated by repeated flash column chromatography f rom lavender oil, while (S)-(+)-linalools with [alpha](D) = +17.4 degrees a nd (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 l inalool, respectively, by using the same method. With the use of an inhalat or, each was administered to subjects both before and after 10 min of work. It was found that administration after work evoked different subjective im pressions when compared with that before work depending on the configuratio n of the isomers and the type of work employed. For instance, inhalation of (R)-(-)-linalool after hearing environmental sounds not only produced a mu ch more favorable impression in the sensory test but was also accompanied b y a greater decrease in beta waves after work in comparison with that befor e 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 fin dings led us to conclude that enantiomeric stereospecificity of linalool ev oked different odor perception and responses not only with chiral dependenc e but also with task dependence. In addition, in comparing these sensory pr ofiling features and IBVA-EEG tendencies between hearing environmental soun d and mental work, a tendency was observed for (R)-(-)-linalool to coincide with (RS)-(+/-)-linalool but not with (S)-(+)-linalool.