Evaluation of the Acute Sedative Effect of Fragrances Based on a Biochemical Marker

Abstract

The purpose of this study is to evaluate the usefulness of a biomarker, salivary amylase, as an indicator of the acute psychological sedative effects of four different types of fragrances. Twenty healthy female subjects in their late 30s were enrolled (36.3 ± 2.5 yr, mean ± SD). In order to induct the subjects a pre-stress, a cold pressor test was conducted as an uncomfortable distress task, prior to the inhalation of test samples. The salivary amylase activity was analyzed before, during and after the inhalation of the fragrance, using a hand-held salivary amylase activity monitor previously fabricated by the authors. Our results indicated that (i) fragrances containing no chemical materials which could directly activate the central nervous system, significantly induced a sedative effect in women, as assessed by both analysis of the biomarker and subjective evaluation; (ii) salivary amylase activity can be an excellent indicator for the evaluation of an acute, psychological sedative effect; and (iii) feel relaxed and refreshed might be a appropriate question to precisely describe the sedative state, rather than the questions fun, stressed or uplifted.

Key Word Index

Biochemical marker, salivary amylase, measurement, sympathetic nervous system, sedative induction.

Introduction

It is thought that there are two pathways for physiological effects of inhaled chemical materials; (i) a chemical material directly activates the central nervous system through mucus and blood circulation, regardless of whedier it can be recognized as a fragrance or not; (ii) a signal sensed by olfaction is transmitted to brain and acts on die memory and emotions. When a person inhales certain narcotics such as cannabis or cocaine, through the nostril, die chemical materials are transported to brain via blood circulation and exert a potent analgesic sedative action. On die otherhand, olfactory perception includes diverse phenomena from chemistry to physiology, commencing widi a chemical signal as a molecule of a certain fragrance, which is then converted into electrical signals that can be recognized in the brain. Buck and Axel (1) identified the genes for olfactory receptors and suggested that there might be approximately 1,000 different types of the olfactory receptor in mammalians. It has been considered that the olfactory information induced by chemosignals, such as a fragrance molecule (2) or pheromone (3,4), is transmitted to the brain through the nervous and endocrine systems, and this signal finally acts directly on the emotions. It has been observed that exposure to the components of plants and flowers by mice directly influenced their motility, either stimulating or sedating the mouse movement, suggesting a direct correlation between olfactory perception and voluntary movement (5,6).

The authors have an interest in the effects of chemosignal-induced olfactory information on the emotions, particularly the quantification of sedative effects in humans. Regarding quantitative evaluation of the physiological effects of fragrance, conventional methods include subjective evaluations by use of a questionnaire (4) and physical measurements such as electroencephalogram (EEG) (7,8), blood pressure (2) and heart rate measurement (9). However, these physical measurements require the subjects to be physicaUy restrained. If an acute psychological effect of fragrance can be quantified under a field-based (namely in use) condition rather than a laboratory-based investigation, it will be possible to quantitatively measure the sedative state induced by a fragrance contained in cosmetics, detergents or household care products, as a measure of comfort or relaxation. Thus, a product manufacturer can evaluate the fragrance ingretdient in a product in order to technically reinforce the commercial innovation idea to consumers.

In contrast, a mediod of quantification of physiological effects has been investigated, based on the biochemical mediod using a biomarker in saliva. Sampling saliva has the advantage that it is non-invasive, which makes multiple sampling easy and does not introduce distress. It is indicated that there are correlations between stress and the measurement of β-endorphin, as well as a criterion standard such as Cortisol (10,11). However, changes in Cortisol reflect activity and reactivity in a completely different physiological system than salivary amylase does. Moreover, there is a lag time in the response of these biomarkers, generally with the reaction being delayed by 20-30 min after the application of the stimuli. Thus, it is considered that these biomarkers may not be suitable for quantitative evaluation of an acute, physiological effect.

Salivary amylase activity was found to increase slighdy with increased flow rates, and large increments in amylase concentration have been observed during sympathetic control by Speirs et al. (12). Salivary amylase activity can be a useful index of plasma norepinephrine concentration under a variety of stressful conditions, since it appears that increased sympathetic nervous activity is a major stimulus of amylase secretion (13,14). Only Morse et al. reported that salivary amylase activity was increased during states of relaxation (15). Although, not only exercise (16-19), but also psychological stresses are able to stimulate salivary amylase (20-24). It has been suggested that salivary amylase may not only function as a digestive enzyme but may also have antibacterial action (25-26). The antibacterial action may be one of the reasons why secretion of salivary amylase is increased by activation of the sympathetic nervous system.