The effects of the inhalation of
Plants synthesize around 200,000 secondary metabolites or specialized phytochemicals, of which essential oils (EOs) constitute an important group [
Geraniol, the major constituent of
Aromatherapy is a traditional treatment that uses EOs. Its effects begin when the aromatic molecule passes through the nasal cavity and adheres to the olfactory epithelium, causing nerve stimulation directly to the hippocampus and limbic amygdaloidal body. This consequently triggers stimuli that control the autonomic nervous system and internal secretory control by changing a number of vital reactions [
Reports in the literature describe the benefits of using EOs in aromatherapy on the wellbeing of individuals, including improvements in mood, stress, anxiety, depression, and chronic pain, and promote so therapeutic, psychological, and physiological effects [
Volatile organic compounds are highly lipophilic and may easily cross the blood-brain barrier and easily exert their neuropharmacological and toxicological effects. While studies on the toxic effects of these compounds are relatively easy to perform, the central effects induced by the perception of odor (e.g., in aromatherapy) are inherently complex. This is why the toxicological studies performed using volatile compounds are much more advanced [
Many studies have been conducted
Since people are often use EOs, it is important to evaluate the possible hepatotoxic effects of these oils. Liver is the main detoxification organ; the catabolism of both endogenous and exogenous compounds takes place in the liver. As a result it is exposure to toxic agents which can cause drug-induced hepatic dysfunction. Therefore, studies on serum activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which are biomarkers of liver damage, are important. The serum activity of ALT and AST is frequently used in clinical settings for diagnostic hepatic toxicity [
Numerous chronic degenerative diseases are associated with oxidative stress, which occurs when there is excess formation of reactive oxygen species (e.g., superoxide, hydroxyl, and hydrogen peroxide) and insufficient defense by the antioxidant system (enzymatic and nonenzymatic). This imbalance between pro- and antioxidants may cause cell injury and death, which consequently lead to tissue dysfunction [
Our aim was to investigate the effect of inhalation of the
The experimental procedure was approved by the Ethical Committee from Institute of Biological Science, São Paulo State University, Botucatu, Brazil, and the animals experiments were carried out in accordance with the principles and guidelines of the Canadian Council on Animal Care as outlined in the Guide to the Care and Use of Experimental Animals.
Male Wistar rats (290–310 g) were reared in polypropylene cages maintained in a controlled environment (temperature
The rats were randomly distributed into three groups (
The rats from all groups were placed individually into chambers (180 mm × 300 mm × 290 mm) adapted from de Almeida et al. [
Food and water consumption were measured daily at the same time and body weights were determined once a week.
After 30 days, the animals were fasted overnight (12–14 h) and euthanized by cervical decapitation under anesthesia (solution containing 10% ketamine chloride and 2% xylazine chloride with a dose of 0.1 mL/100 g body weight). Blood was collected and the serum was obtained by centrifugation at 6000 rpm for 15 minutes. Serum glucose was determined using an enzymatic colorimetric method after incubation with glucose oxidase/peroxidase. The total amount of protein was estimated using the biuret reagent and the total cholesterol concentration was determined using the cholesterol esterase/oxidase enzymatic procedure. Triacylglycerols levels were measured by enzymatic hydrolysis and the final formation of quinoneimine, which is proportional to the concentration of triacylglycerols present in the sample. Serum urea was determined by addition of urease and phenol-hypochloride, which leads to the formation of an indophenol-blue complex. The serum creatinine levels were estimated using a reaction with picric acid in alkaline buffer to form a yellow-orange complex, whose color intensity is proportional to the creatinine concentration in the sample. ALT and AST activities were determined by using pyruvate and oxaloacetate as substrates, wherein NADH is converted into NAD+ proportional to the activities of these enzymes. Hepatic samples (200 mg) were removed and homogenized in 0.1 M phosphate buffer, pH 7.4, using a Teflon-glass Potter-Elvehjem homogenizer. The homogenate was centrifuged (10,000 g for 15 minutes) and the supernatant was used to determine the concentration of hepatic lipid hydroperoxide (LH) and activities of antioxidant enzymes. Lipid hydroperoxide activity was determined by the oxidation of Fe+2 in the presence of a reactive mixture containing methanol, xylenol orange, sulfuric acid, and butylated hydroxytoluene. Catalase activity was assayed using phosphate buffer containing hydrogen peroxide. The activity of glutathione peroxidase (GSH-Px) was determined in the presence of phosphate buffer, NADPH2, reduced glutathione, and glutathione reductase. Superoxide dismutase (SOD) activity was assayed according to the method by measuring the rate of reduction of nitroblue-tetrazole (NBT) in the presence of free radicals generated by hydroxylamine.
Results are expressed as the mean ± SD. The statistical significance between the groups was assessed using one-way analysis of variance (ANOVA) with Tukey’s test to compare the means of the experimental group. The probability with
Inhalation of geraniol (G2) and of
General characteristics and serum protein levels after 30 days for all experimental groups.
Parameters | Groups | ||
---|---|---|---|
G1 | G2 | G3 | |
Final body weight g | 348.57 ± 43.65 | 328.40 ± 29.82 | 320.98 ± 39.90 |
Body weight gain g | 37.47 ± 9.25 | 36.86 ± 8.22 | 38.53 ± 17.06 |
Final food consumption g/day | 20.30 ± 4.40 | 19.25 ± 4.14 | 18.52 ± 3.78 |
Final water consumption mL/day | 248.75 ± 21.84c | 248.75 ± 16.20c | 211.88 ± 10.67a,b |
Serum protein g/dL | 5,13 ± 0,83 | 5,39 ± 1,39 | 5,95 ± 1,13 |
Values are given as the mean ± SD for each group of eight animals. aSignificantly different from G1;
Serum glucose, total cholesterol, and triglycerides levels after 30 days for all experimental groups. Values are given as the mean ± SD for each group of eight animals.
Serum urea and creatinine levels after 30 days for all experimental groups. Values are given as the mean ± SD for groups of eight animals each.
ALT activity was higher in the group exposed to geraniol when compared to the other groups, which did not differ from each other. No change was found in the AST activity between the groups (Figure
Serum activity of ALT and AST after 30 days for all experimental groups. Values are given as the mean ± SD for each group of eight animals.
Hepatic lipid hydroperoxide levels after 30 days for all experimental groups. Values are given as the mean ± SD for each group of eight animals.
Hepatic activities of catalase, SOD, and GSH-Px after 30 days for all experimental groups. Values are given as the mean ± SD for each group of eight animals.
EOs are widely used in aromatherapy procedures and there is interest in reports on the hepatic toxicity of these natural products. However, few studies have explored the effects of EOs on an organism when administered by inhalation. Since EOs have been extensively used in aromatherapy due to their therapeutic properties and also used in food products, in dermatology, and in the fragrance and cosmetic industries [
There were no changes in serum glucose levels between the groups, indicating maintenance of glycemic homeostasis in these animals. However, other experimental studies have demonstrated that
The inhalation of both geraniol (G2) and
Our results are also in agreement with Costa et al. [
Since urea is formed in the liver and excreted by kidneys, estimation of this nitrogenous compound in the bloodstream is important to estimate both hepatic and renal functions. Animals treated with geraniol and EO did not show altered serum urea levels, suggesting a normal degree of protein catabolism, which was confirmed by a normal concentration of hepatic protein. Although there was no alteration in the levels of serum urea in the G2 group, we cannot exclude the involvement of possible changes in the glomerular filtration rate in these animals. In clinical practice, serum creatinine, a biomarker for renal failure, is used as an indicator of renal function [
Plasma membrane damage from some cells types, such as hepatic cells, is accompanied by release of cytosolic enzymes into bloodstream, a phenomenon that always occurs under several pathophysiological conditions [
ROS, such as superoxide anion (
Lipid peroxidation is an important toxic event because involves the removal of hydrogen from fatty acid chains mediated by ROS [
The endogenous antioxidant enzyme includes superoxide dismutase that catalyzes the dismutation of superoxide radicals [
Significantly high LH was observed in rats exposed to geraniol (G2), while the beneficial effect of
Rats exposed to geraniol (G2) had higher catalase, SOD, and GSH-Px activities, indicating that antioxidant enzyme activities were not sufficient to inhibit the ROS action and, consequently, the lipoperoxide generation in liver of these animals.
According to Koek et al. [
Since lipid hydroperoxide has been widely studied as marker of lipoperoxidation [
In another study, geraniol reduced lipid peroxidation and inhibited the release of NO, indicating its possible antioxidant potential in inflammatory lung diseases, in which oxidative stress plays key role in these pathogenesis [
In conclusion,
Essential oil
Essential oils
Alanine aminotransferase
Aspartate aminotransferase
Reactive oxygen species
Lipid hydroperoxide
Glutathione peroxidase
Superoxide dismutase
Nitroblue-tetrazole.
The authors declare that there is no conflict of interests regarding the publication of this paper.