Smelling lavender and rosemary increases free radical scavenging activity and decreases cortisol level in saliva
Introduction
In recent years, there has been an increasing interest in free radicals, reactive oxygen species (ROS), and antioxidant defense mechanisms and oxidative stress in degenerative diseases (Halliwell et al., 1992, Battino et al., 1999). Oxygen is required for all mammalian energy needs. But the reduction of molecular oxygen to water is accompanied by the production of free radicals and/or reactive oxygen species (ROS) (Davies, 1995). Therefore, the body possesses several antioxidant systems (free radical scavenging activity, FRSA) that are very important for the prevention of oxidative stress, and saliva contains such activity (Mandel, 1987, Nagler et al., 2002, Battino et al., 2002). Oxidative stress is produced when the dynamic redox balance between oxidative and various antioxidant systems is intensity shifted toward oxidative potentials (Sies, 1997).
Individual antioxidant moieties, enzymatic or nonenzymatic, play specific roles in combating oxidative stress and the measurement of single antioxidants may be beneficial to some studies. However, individual results may not be indicative of the overall effect of multiple antioxidants working in concert with one another. The capacity of known and unknown antioxidants, their cumulative action and the synergistic interaction of all the antioxidants present in body fluids are all of considerable importance to understand. Therefore, an important index that could be used in oxidative stress studies may be the measurement of the total antioxidant potential of the biological system (Ghiselli et al., 2000, Serafini and Rio, 2004).
We have focused on non-protein low-molecular fractions in saliva, and designed a simple method of determining total FRSA based on the reduction of a stable radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH) (Atsumi et al., 1999). In the report, we found that the FRSA of saliva using DPPH was correlated to that of serum (Atsumi et al., 1999). Saliva samples are useful in order to measure the effects of physical and mental changes. We previously reported that FRSA decreased in response to physical stimulation (fatigue of exercise) (Atsumi et al., 1999), and increased in response to pleasant mental stimulation (watching a pleasant video) (Atsumi et al., 2004) and the inhalation of a pleasant aroma (Atsumi and Tonosaki, 2003). We have recently clarified that lavender, which is widely used in aromatherapy, stimulates parasympathetic nerves and increases FRSA, while a typical unpleasant odor, isovaleric acid, does not increase FRSA, but increases the level of a stress hormone, cortisol (Atsumi and Tonosaki, in press). Lavender essential oil contains abundant esters and has the main action of relaxation, under the control of parasympathetic nerves, as well as sedative and anticonvulsive actions on the nervous system (Cavanagh and Wilkinson, 2002, Lis-Balchin and Hart, 1999). On the other hand, rosemary essential oil contains abundant oxides and monoterpenes, and has the main action of stimulating the nervous system under sympathetic control, leading to increases in memorizing and concentrating abilities (Sanders et al., 2002). In a former study, it was not clear whether pleasant smell stimulation could universally increase FRSA, or if this effect was restricted to lavender, which having a sedative activity activates parasympathetic nerves.
Therefore, in the present study, using both lavender, (parasympathetic nerve stimulation) and rosemary (sympathetic nerve stimulation) at high and low concentrations, salivary FRSA was measured. At the same time, physiological substances in saliva: cortisol, secretory IgA, and α-amylase activity, were measured, and the free radical scavenging effects of the aromas and their mechanisms were investigated. An inverse correlation was noted between FRSA and the cortisol level.
Section snippets
Subjects
The subjects were 22 healthy volunteers who understood the objective of this study and consented verbally to cooperate in the experiment according to university guidelines. (lavender experiment: 10 males and 10 females, aged 22.7 years on average; rosemary experiment: 15 males and 7 females, aged 22.5 years on average). Eating, smoking cigarettes, and strenuous exercise were prohibited from 1 h before the experiment. The experiments were performed between 16:30 and 17.30 h every day.
Test solution
Commercial
Changes in FRSA
Changes in salivary FRSA stimulated by the smells of lavender and rosemary are shown in Fig. 1. In the lavender experiment (a), the median FRSA values for 20 subjects after stimulations with A, B, and C were 38.21, 40.72, and 36.03 μmol/ml, respectively, showing a significant increase at the low concentration (B) compared with the control (A) (P < 0.05), but no significance was noted at the high concentration (C). The increases in rates for A were 1.0, 1.11, and 1.09 for A, B, and C, respectively.
Discussion
In our previous report (Atsumi and Tonosaki, in press), the pleasant smell of lavender potentiated salivary FRSA, but the unpleasant smell of isovarelic acid did not change it. In this study, the smells of both lavender (Fig. 1a) and rosemary (Fig. 1b) increased FRSA. The effect of lavender was exhibited at a low concentration, whereas that of rosemary was exhibited at a high concentration. Generally, an excessively high concentration of smell is felt to be unpleasant (Moskowitz and Gerbers,
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