2009; but see Wysocki et al. Overall, acute toxic effect of eugenol in mammals is low, and the US Environmental Protection Agency has classified eugenol as category 3; the oral LD 50 value is >1930 mg kg −1 in rodents.
Finally, because anosmics can differ from normosmics with respect to irritation sensitivity, anosmics may not be a perfect model (Frasnelli et al.
All aspects of the study were approved by the University of Pennsylvania Institutional Review Board.
2011).
For eugenol, the mean number correct was 10.1 (SD ±1.2) (Figure 1).
Thresholds were obtained using a similar 2-alternative forced-choice modified staircase method.
An additional group of subjects attempted to lateralize a higher fixed concentration of eugenol (neat) to provide additional evidence that intranasal eugenol can stimulate the trigeminal nerve. Their ages ranged from 22 to 39 (mean ± standard deviation [SD] = 30 ± 10.4), and all signed informed consent approved by the University of Pennsylvania Institutional Review Board. Published work suggests that people are unable to lateralize volatile chemicals based on olfaction but are able to do so when concentrations reach levels high enough to feel (Kobal et al.
Furthermore, it may not be possible to depend on published results, unless the method of stimulation is exactly the same. We used eugenol (CAS 97-53-0: Sigma Aldrich, >99% pure) and L-menthol (menthol; CAS 2216-51-5: Fisher Scientific, Acros Organics, labeled >99% pure). Olfactory Deprivation and Enrichment: An Identity of Opposites? The subjects were able to detect eugenol (to discriminate it from a blank), and the staircase procedure was able to successfully characterize ODTs for the compound in all participants. 2009 ).
Details of the correlation between IR patterns in these two regions and ring substitution are available in the literature references linked in the left frame (especially the books by Shriner and Fuson, Silverstein et. Spectroscopy: Structure Determination.
The characteristic overtones are seen from about 2000-1665. This is a very useful tool for interpreting IR spectra: Only alkenes and aromatics show a CH stretch slightly higher than 3000 cm.
In a previous experiment, anosmics reported that this common flavor and fragrance ingredient did not produce noticeable irritation (Doty et al. After both sets had been sampled, the subject indicated which set contained the odorant. Both the olfactory and the trigeminal systems are able to respond to intranasal presentations of chemical vapor. Implications and strategies for selection of model odorants are discussed.
Of 11 subjects, 9 were able to correctly lateralize the eugenol-stimulated side, which was significantly greater than chance according to binomial statistics (P = 0.027).
Two identical sets for each odorant were used to allow the headspace to regenerate between trials. In contrast, the distinction is critical in laboratory experiments that focus on olfaction or interactions between olfaction and chemesthesis (Cain and Murphy 1980; Hummel et al. 2003). 2003). Rather than searching for a “pure odor,” a more direct solution is to present a lower concentration that is able to produce a clear odorous sensation but without rendering a measurable trigeminal response.
2011).
To take one example, Chen et al. In each block of trials, stimulation of the left or right nostril followed a pseudorandomized sequence, with each nostril stimulated either 5 or 6 times. 2009). Based on these data, we recommend that eugenol should not be used in chemosensory experiments unless the expressed interest is merely to produce the perceptual quality of cloves.
However, eugenol has long been used as local anesthetic in dentistry (Lee et al. X ÿÿ ÿÿ ÿÿ ¤ , Š
Menthol crystals (20 g) also were presented in identical amber glass sniff bottles. These results support those of Experiment 2 in suggesting that intranasal eugenol in fact does stimulate the trigeminal nerve and agree with the findings of Hummel and Kobal (1994) and Cometto-Muñiz et al.
1997), a procedure that is commonly used by chemosensory researchers to measure olfactory thresholds (Wysocki and Wise 2003). Regardless, one should keep in mind that compounds that produce no clear irritation at room temperature may do so when vapor-phase concentration is increased by heating, although this does not occur for vanillin (Cometto-Muñiz et al. The current experiments studied nasal lateralization of eugenol more thoroughly, using 3 different experimental methods.
This is a very useful tool for interpreting IR spectra: Only alkenes and aromatics show a C–H stretch slightly higher than 3000 cm-1. al., and the Aldrich Library of IR Spectra). Eugenol, a phenylpropene extracted from clove oil, nutmeg, cinnamon, basil, and bay leaf, is a particularly interesting stimulus.
How to Identify Carbonyls, Alkenes, Alkynes, and Aromatics in the IR Spectrum; How to Identify Carbonyls, Alkenes, Alkynes, and Aromatics in the IR Spectrum . The =C–H stretch in aromatics is observed at 3100-3000 cm-1.
2005; Frasnelli, Hummel, et al. The lateralization threshold was then calculated as the mean of the concentration of irritant at which the 4 reversals occurred.
IR (infrared) spectroscopy is useful in organic chemistry because it enables you to identify different functional groups. Neat eugenol (20 mL) was presented in amber glass sniff bottles (as described above for Experiment 1). Other work, however, has shown that eugenol can be lateralized when presented monorhinally (Hummel and Kobal 1994) or when presented roughly 3 times in a session, over multiple sessions, in which 12 odorants were evaluated for nasal lateralization (Cometto-Muñiz et al. Filtered light mineral oil served as a blank in lateralization trials but was not tinged because amber bottles were used. 2009) and has for many years been used as such in dentistry clinics (though it has not been shown that sniffing eugenol vapor can anesthetize the nasal mucosa). The sequence terminated after at least 5 legitimate reversals had occurred. Oxford University Press is a department of the University of Oxford. The purity of the eugenol was verified using gas chromatography/mass spectrometry to ensure that lateralization performance was unlikely to be influenced by trace contaminants.
4 ”. 2004). Regardless, the extent to which eugenol stimulates the trigeminal nerve will almost certainly depend on concentration and method of presentation, which future studies can elucidate in more detail.
Most volatile compounds can stimulate both sensory systems, though higher concentrations are generally required to stimulate the trigeminal nerve. Thus, we prepared and presented 11% (v/v) eugenol (diluted as above) versus a blank (diluent only) and asked 11 individuals (2 males) to take a single sniff from the Teflon nosepieces atop the bottles (the nostril that received eugenol was randomized). 2005).
In Experiment 2, subjects attempted to lateralize a moderate fixed concentration in a single trial. The olfactory system detects chemicals using specialized receptor neurons distributed on a limited dorsal area of the nasal mucosa and sends signals to the brain via the first cranial (olfactory) nerve.