where the independent variables are solute descriptors: π 2 H is the dipolarity/polarizability, ∑α H 2 and ∑β 2 H are the overall or effective hydrogen-bond acidity and basicity, and L 16 is the solute Ostwald solubility coefficient on hexadecane at 25 °C. Surprisingly, the aliphatic aldehydes and carboxylic acids fit the correlation and with respect to nasal pungency thresholds in man for brief (1-3 s) presentations must be regarded as `nonreactive' compounds. It is suggested mere transport of the compound from the air stream to the receptor area largely determines the potency to produce pungency. Various chemical properties of the receptor area are deduced from the coefficients in Eq. i.

is the gas-hexadecane partition coefficient. The number of data points is n, the correlation coefficient is r, the standard deviation is sd, and F is the F-statistic. LogSP is then either [log(DES/P o ) -0.66], or log(1/EIT). It is suggested that equation i can be used to predict eye irritation of organic vapours and pure liquids as eye irritation thresholds.Abbreviations: DES = Draize eye scores; EIT = eye irritation threshold; VOCs = volatile organic compounds.3

No abstract

COMETTO-MUÑIZ, J. E., W. S. CAIN, M. H. ABRAHAM AND R. KUMARSINGH. Trigeminal and olfactory chemosensory impact of selected terpenes. PHARMACOL BIOCHEM BEHAV. In Experiment 1, four normosmics and four anosmics (3 congenital, 1 idiopathic) provided odor and nasal pungency thresholds, respectively, for the following terpenes: ∆ 3 -carene, p-cymene, linalool, 1,8-cineole, and geraniol, plus the structurally-related compound cumene. Additionally, all subjects provided nasal localization (i.e., right/left) and eye irritation thresholds. Trigeminally-mediated thresholds (i.e., nasal pungency, nasal localization, and eye irritation) lay about three orders of magnitude above odor thresholds -which ranged between 0.1 and 1.7 ppm. The results implied uniform chemesthetic sensitivity across tasks and sites of impact. In Experiment 2, normosmics and anosmics provided odor and nasal pungency thresholds, respectively, for three pairs of isomeric terpenes: α-and γ-terpinene, α-and ß-pinene, and R(+)-and S(-)-limonene.Odor thresholds ranged between 1.4 and 19 ppm -that is, about an order of magnitude higher than those of the previous terpenes -with no substantial differences between odor thresholds of members of a pair. Regarding chemesthetic impact, only α-terpinene evoked nasal pungency. The overall outcome suggests comparable trigeminal chemosensitivity between nose and eyes and between normosmics and anosmics, as shown before for homologous n-alcohols. It also lends support to a previously-derived solvation model of the chemesthetic potency of airborne substances, and indicates the likely importance of certain molecular-size restrictions for effective trigeminal impact.

: Draize eye scores (DES) of 37 pure organic liquids have been converted into scores for the corresponding vapors, DES/P0, where P0 is the liquid vapor pressure in atmospheres at 298 K. It is shown that there is a constant difference of 6.7 between values of log(DES/P0) and log (1/EIT), where EIT is the eye irritation threshold in parts per million (ppm, by volume) of eight vapors for human subjects. The 37 log(DES/P0) values can be combined with log(1/EIT) values for 17 vapors into one quantitative structure‐activity relationship (QSAR) for sensory potency (SP) using our general solvation equation, where R2 is an excess molar refraction, π2H the compound polarizability/dipolarity, Σα2H and Σβ2H are the compound hydrogen‐bond acidity and basicity, and L16 is the gas‐hexadecane partition coefficient at 298 K. n is the number of data points, r the correlation coefficient, SD the standard deviation, and F the F‐statistic. LogSP is then either [log(DES/P0) ‐ 0.66] or log (1/EIT), confirming the result for the eight common compounds. It is suggested that the equation can be used to predict eye irritancy of organic vapors and pure liquids. It is further suggested that for the compounds in the data set, the main process in eye irritation is transfer of the compound from the vapor or pure liquid to a biological phase, and a number of chemical properties of the biological phase have been mapped out through the equation. These properties are consistent with corresponding properties for a number of organic liquid phases.