Biomedical subjects

R Kumarsingh

Publications and source records attributed to R Kumarsingh.

4 recordsLinked to original sources

PubMed1998

Sensory properties of selected terpenes. Thresholds for odor, nasal pungency, nasal localization, and eye irritation.

We tested four normosmics and four anosmics in detection thresholds for six terpenes commonly found indoors: cumene, p-cymene, delta-3-carene, linalool, 1,8-cineole and geraniol. Normosmics provided odor thresholds and anosmics provided nasal pungency thresholds. All subjects provided nasal localization (i.e., right/left nostril) and eye irritation thresholds. Each type of threshold was measured eight times per subject-stimulus combination. Stimuli were presented from squeeze bottles in a two-alternative forced-choice procedure via an ascending method of limits. Odor thresholds ranged between 0.1 and 1.0 parts per million (ppm, by volume). Nasal pungency thresholds lay about three orders of magnitude above odor thresholds. Nasal localization and eye irritation thresholds did not differ between normosmics and anosmics, and fell close to nasal pungency thresholds. Olfactory thresholds could be obtained for all stimuli in all repetitions using the criterion of five correct choices in a row. Trigeminal thresholds (i.e., pungency, localization and eye irritation) could be obtained on all repetitions only for some terpenes using that same criterion. Carene and cineol produced nasal pungency and eye irritation on all repetitions. None of the terpenes could be localized on all repetitions, but cineol was localized a higher percentage of instances than were the other stimuli. At the other extreme, geraniol failed to evoke any of the three trigeminal responses in most instances. Overall, the results indicate that the three trigeminal thresholds produce a uniform view of the potency of these terpenes, with nasal pungency and eye irritation being slightly more sensitive than nasal localization. Furthermore, application of a previously derived linear solvation energy relationship to the results reinforced the view that physicochemical properties can predict the chemesthetic impact of volatile organic compounds.

Eye↗

PubMed1998

Draize eye scores and eye irritation thresholds in man can be combined into one QSAR.

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, [formula: see text] where R2 is an excess molar refraction, pi 2H is the compound polarizability/dipolarity, sigma alpha 2H and sigma beta 2H 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.

Animals↗

PubMed1998

An algorithm for nasal pungency thresholds in man.

Nasal pungency thresholds (NPT) in man have been determined by Cometto-Muniz and Cain for 44 varied compounds, including esters, aldehydes, ketones, alcohols, carboxylic acids, aromatic hydrocarbons and pyridine. With the exclusion of acetic acid, 43 of these NPT values are well correlated through the general linear free energy equation of Abraham, leading to the algorithm, log(1/NPT) = -8.519 + 2.154 pi(2)H + 3.522 sigma alpha(2)H + 1.397 sigma beta(2)H + 0.860 logL16. N = 43, r2 = 0.955, SD = 0.27, F = 201 (i) where the independent variables are solute descriptors: pi(2)H is the dipolarity/polarizability, sigma alpha(2)H and sigma beta(2)H are the overall or effective hydrogen-bond acidity and basicity, and L16 is the solute Ostwald solubility coefficient on hexadecane at 25 degrees 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.

Air Pollutants↗

PubMed1998

Trigeminal and olfactory chemosensory impact of selected terpenes.

In Experiment 1, four normosmics and four anosmics (three congenital, one idiopathic) provided odor and nasal pungency thresholds, respectively, for the following terpenes: delta3-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 thresholis. 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: alpha- and gamma-terpinene, alpha- and beta-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 alpha-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.

Acyclic Monoterpenes↗