Structure-odour relationship

Takane, S.-Y. and Mitchell, J.B.O. (2004) A structure-odour relationship study using EVA descriptors and hierarchical clustering. Org. Biomol. Chem.,... 

M. G. J. Beets, Structure-Activity Relationship in Human Chemoreception. Applied Science Publishers. London, 1978. B. Winter, Helt Chim. Acta, 72, 1278 (1989). 141. Ring-opened Analogues of Ambrox. Synthesis and Structure Odour Relationships. 

Multivariate data obtained from different strains of bacteria are especially suitedforPCA mostexamplesthusconcemantibacterials [1,20-25,181,184,187, 208]. Other applications deal with herbicides [26], opioids [4], structure-odour relationships [186], anti-inflammatory compounds [27, 182] and with the quantification of toxic compounds [207], respectively. Niemi et al. carried out a PCA of 90 molecular connectivity indices and needed eight PCs to explain more... 

Partial least squares regression analysis (PLS) has been used to predict intensity of sweet odour in volatile phenols. This is a relatively new multivariate technique, which has been of particular use in the study of quantitative structure-activity relationships. In recent pharmacological and toxicological studies, PLS has been used to predict activity of molecular structures from a set of physico-chemical molecular descriptors. These techniques will aid understanding of natural flavours and the development of synthetic ones. 

Chastrette, M., Zakarya, D. and Peyraud, J.F. (1994). Structure-Musk Odour Relationships for Indan and Tetralins Using Neural Network. On the Contribution of Descriptors to Classification. Eur.J.Med.Chem., 29, 343-348. 

Wagner R., Czerny M., Bielohradsky J, and Grosch W. (1999) Structure-odour-activity relationships of alkylpyr-azines. European Food Res. Technol., 208, 308-16. 

The problem is further complicated by the fact that the detection threshold of a chemical compound in a complex odour can differ from that when it is on its own, i.e. as a simple odour. For example, compound A and B may not smell as individuals but when mixed together they do elicit an olfactoiy response. Thus, the structure-activity relationship may be straightforward and exist for simple odours but can be highly non-linear in mixtures. This makes it very difficult to understand and model the mechanisms by which the human olfactory system works and thus to develop an electronic analogue. 

Syst., 48, 35-46 (1999). Structure-Camphor Odour Relationships using the Generation and Selection of Pertinent Descriptors Approach. 

Another approach ( biogenetic analyses ) involves considerations of a reasonable biogenesis of a target compound. Reflections on relationships of components which belong to the same odour bouquet or which have already been known from related species may suggest structures to be expected and, thus, be helpful in the identification process. 

The relationship between odour quality and chemical structure is of considerable practical and theoretical interest. A numt r of methods have been used to determine quantitatively the relationships between the structure of a molecule and its odour quality (7). Though quantitative results were not obtained, a number of interesting theories were present in that the intermolecular interaction in olfaction involved electrostatic attraction, hydrophobic bonding, van der Waals forces, hydrogen bonding, and dipole-dipole interactions. Hydrophobic interactions also appeared to be a major force for substrate binding in olfaction. It had previously been shown that lipophilicity and water solubility were factors diat significandy influenced the odour thresholds of the pyrazines (8),... 

Another common failing in the logic behind odour theories is the inability to distinguish between cause and effect. All too often, someone finds a correlation between two parameters and assumes a causal relationship, without asking whether this correlation could simply be between two effects of a common cause. An example of this in the field of olfaction is the assumption that a correlation between the infrared spectra of a set of odorants and their odours demonstrates that the odour was caused by those specific vibrations. The odours and the spectra are both effects of a common cause, that is, the molecular structure. 

P. Laffort, Relationships between Molecular Structure and Olfactory Activity, in Odours and Deodorization in the Environment, G. Martin and P. Laffort (eds), VCH, 1994. 

ADAPT has been developed and used by Jurs in a wide range of S AR applications. In the field of olfaction, these include the correlation of odour intensities for 58 structurally and organoleptically diverse odorants (Edwards and Jurs, 1989), and the investigation of the relationship between molecular structure and musk odour (Jurs and Ham, 1977 Ham and Jurs, 1985 Narvaez et al., 1985). To date, no one has used pattern-recognition techniques in the study of muguet odorants. 

Although there has been much study of the relationship between the structure and the sensory activity of odorous molecules, it frequently appears impossible to predict the odour from its chemical structure. In other words, very similar chemical structures can have quite different smells (e.g. the para versus the meta form, optical isomers). Contrarily, different compounds in terms of functional group, shape, etc can have similar smells [2]. 

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