[P27] Chemo-Biological Analysis Applied to the Olfaction Field

International audienceHuman are surrounded by numerous odorant molecules in the air from a limited number of olfactory receptors (1), and the odor perceived from these molecules does not comes from the isolated molecules but from their mixture (2). According to the odor perceived from the mixture, we differentiate the heterogeneous perception which is the distinction between the odor components of the mixture and the homogeneous perception that corresponds to the perception of a single odor from the mixture preventing the distinction between odor components of the mixture. There are two types of homogeneous perceptions: the masking and the blending mixture. Masking occurs when one of the mixture components covers the other constituents and we can only smell the odor of one of the mixture components. And, we will speak of blending mixture when the perceived odor is different from each of the mixture components. In the present study, we focus on both types of homogeneous perception with a red cordial (RC) mixture involving vanillin, isoamyl acetate, frambinone, ethyl acetate, beta-ionone, beta-damascenone (blending mixture) (3) and a woody-fruity mixture (masking mixture) involving whiskey lactone (WL) and isoamyl acetate (IA) (4). The aim was to improve the understanding about homogeneous perception combining classification and pharmacophore approaches. By collecting from different data sources, we built a large dataset listing more than 5000 odorant molecules associated with their odors. Using the fingerprints representing the structure of these molecules, we performed a dimension reduction by the Uniform Manifold Approximation and Projection and then a Self-organizing map (SOM) classification on the coordinates of the reduced dimensions that led to define specific clusters. Pharmacophore modeling was performed to determine the presence of common features between the molecules for each of the mixtures. We used (i) subsets of the components of the aroma mixtures; and (ii) subsets of about ten of molecules selected on the basis of their odor notes in the SOM clusters containing the components of the mixtures. About the masking, relevant hypotheses were obtained from the WL and IA subsets, unlike the subsets constituted by the RC mixture components, from which no relevant hypotheses were generated. These results suggest that WL and IA could have common binding sites while the components of RC mixture have probably not. Consequently, two different ways for the formation homogeneous perception could exist. The configural perception of the masking could take place at the peripheral level whereas for the RC mixture, the configural perception might rather require the signal integration at higher levels, in the olfactory bulb and/or in the brain