Quantitative structure-odor intensity

Approach was used in deriving mechanistic information about odor intensity as well as insight into how this biological activity may be predicted. This paper will first briefly describe the history of QSAR, the QSAR parameters used, and how substituents for QSAR studies are selected. Several examples of the Hansch Approach used in taste and odor quality studies will next be presented. The balance of the paper will deal with the development of quantitative structure odor intensity relationships which will further expand upon the earlier study reported by this author (11). For example, the use of relatively new QSAR steric parameters in correlations with odor intensity data, and correlations of log P with literature odor intensity data determined on animal panels will be presented. This will be followed by conclusions derived from those studies, and areas of future work. 

The procedures for doing the quantitative structure odor intensity relationship study involved the following ... 

Egolf, L.M. and Jurs, P.C. (1993b). Quantitative Structure-Retention and Structure-Odor Intensity Relationships for a Diverse Group of Odor-Active Compounds. AnaLChem., 65, 3119-3126. 

The use of computer techniques in the correlation of biological activity with substrate physical-chemical properties has received much attention in the area of medicinal chemistry. The use of these techniques, denoted Quantitative Structure Activity Relationships (QSAR), were developed mostly by Hansch and his coworkers eind have been reviewed by Tute te), Purcell et. al. (9) and Dunn (10). These techniques were utilized by Greenberg (1 l) ln the correlation of odor threshold and suprathreshold data with Log P, the log (n-octanol/water partition coefficient). In the same study it was reported that steric and polar effects as measured by the Taft Steric and Polar Constants poorly correlated with odor intensity data. 

The physicochemical approach to odor detection involves instrumental analysis of the chemical structure and concentration of an odorant. The relationship between the sensation of an odor as perceived by a human and the physical or chemical properties of the odor is not as simple as other sensations such as color or sound, which can be related to known physical forms such as intensity and wavelength. Measurement of odorant structure and concentration is possible through quantitative chemical analytical techniques. The ideal situation is to develop an instrument that is capable of replicating the human olfactory system without the added problems of human variability, sensitivity, and perception. 

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