Aromatherapy and plant-based essential oils are widely used as complementary and alternative therapies for symptoms including anxiety. Furthermore, it was reportedly effective for the care of several diseases such as Alzheimer’s disease and depressive illness. To investigate the pharmacological effects of essential oils, we developed an
Trace nutrients contained in plants such as vitamins and minerals are essential for human health. Essential oils used in aromatherapy are also useful for health maintenance as with these trace nutrients contained in plants. Aromatherapy is one of the folk remedies that encompasses the use of essential oils derived from various types of plant sources for a variety of application methods and is widely used as a complementary and alternative therapy for symptoms including anxiety and depression [
The prevalence of senile dementia, such as Alzheimer’s disease (AD) and vascular-type senile dementia (VD), is increasing worldwide. In senile dementia, marked death of neurons in the cerebral cortex and hippocampus is observed. However, the prime cause of neuronal death is identical. VD is a cerebrovascular disease and mainly occurs after transient global ischemia. It is widely accepted that excess zinc (Zn) which is secreted during ischemia conditions causes neuronal death and plays a central role in the pathogenesis of VD. Meanwhile, it is widely accepted that the oligomerization of
Following this need, we attempted to evaluate the pharmacological effects of aromatic oils employing our previously developed rapid, sensitive, and convenient assay system for high-throughput screening of such substances using GT1–7 cells (immortalized hypothalamic neurons) [
TMX was purchased from Sigma Aldrich (St. Louis, MO, USA). This compound was diluted in dimethyl sulfoxide (DMSO) prior to use. H2O2 was purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). AlCl3, ZnCl2, and maltol were purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). Al was reacted with maltol to yield the Al-maltol complex to increase the cell membrane permeability of Al. AlCl3 and maltol were diluted in distilled water at a molar ratio of 1 : 3 and used as an Al-maltol complex solution. In this study, the concentration of Al equals the concentration of Al3+ in the Al-maltol complex solution. The essential oils were purchased from GAIA/NP (Tokyo, Japan) and diluted by adding 99.5% ethanol just before use. All of the essential oils used in this study are shown in Table
Characteristics of the essential oils.
Name | Abbreviation in Figures | Scientific name | Major component |
---|---|---|---|
Benzoin | BE |
|
Benzoic acid, benzyl benzoate, benzyl alcohol |
Bergamot | BM |
|
Linalyl acetate, limonene, linalool |
Chamomile | CH |
|
Chamazulene, |
Clove | CL |
|
Eugenol, |
Damask rose | DR |
|
Citronellol, geraniol, nerol |
Eucalyptus | EU |
|
1,8-Cineole |
Fennel | FE |
|
Anethole, fenchone, limonene |
Frankincense | FR |
|
|
Geranium | GE |
|
Citronellol, geraniol, limonene, |
Ginger | GI |
|
|
Grapefruit | GR |
|
Limonene, myrcene, |
Kabosu | KB |
|
Limonene, myrcene |
Lavender | LA |
|
Linalool, linalyl acetate |
Lemon | LE |
|
Limonene, |
Lime | LI |
|
|
Mandarin | MD |
|
|
Myrrh | MI |
|
Cuminaldehyde, limonene, |
Neroli | NE |
|
Linalool, limonene, trans-ocimene |
Orange | OR |
|
|
Rosalina | RS |
|
Linalool, 1,8 cineol, |
Rose | RO |
|
Citronellol, geraniol |
Rosemary | RM |
|
Camphene, |
Rosewood | RW |
|
Linalool, |
St. John’s wort | SW |
|
|
Ylang Ylang | YY |
|
Germacrene D, |
GT1–7 cells (provided by Dr. R. Weiner, University of California at San Francisco) were grown in Dulbecco’s Modified Eagle’s Medium/Nutrient Mixture F-12 Ham (DMEM/F-12) supplemented with 10% fetal bovine serum. After enzymatic digestion using trypsin, the cells were resuspended in a serum-free medium and plated onto culture plates [
Cell viability was assessed as described previously [
All statistical evaluations were performed using two-tailed Student’s
We examined the effects of essential oils on the viability of immortalized hypothalamic neurons (GT1–7 cells). Figure
GT1–7 cell viability after exposure to various essential oils. GT1–7 cells were treated with 25 ppm of various essential oils. After 24 h, the viability was analyzed using the WST-1 method. Data are presented as the mean ± SEM (
Cytotoxicity of H2O2, Al, Zn, and TMX. GT1–7 cells were treated with 20–50
The effect of essential oils on GT1–7 cells exposed with various cytotoxins. GT1–7 cells were treated with 20
With H2O2
With Al-maltol
With Zn
Dose response
The effect of essential oils on TMX-induced GT1–7 cell cytotoxicity. (a) GT1–7 cells were treated with 0.5
With TMX
Dose response
GT1–7 cells were treated with various essential oils and cytotoxic agents (H2O2, Al, and Zn) to investigate the protective activities of essential oils against neurotoxicity. H2O2 is known to produce a hydroxyl radical, thereby inducing cytotoxicity. Neuronal Al accumulation can result in neuron dysfunction and toxicity [
As shown in Figure
Damask rose and lemon oil increased the viability of Al-treated GT1–7 cells (Figure
The GT1–7 cell line is also a useful model for the investigation of endocrine-disrupting effects, and the antagonist of ER (TMX) was used to induce GT1–7 cell death [
We showed the effects of various essential oils on multiple kinds of cytotoxicity using a convenient
The GT1–7 cell line is a useful model of the neuroendocrine system, and the
The authors declare no conflict of interests.
The authors would like to thank Ms. Ayako Shimura, Ms. Noriko Itakura, Ms. Yui Tamura, Ms. Kaori Masaki, Mr. Naoya Murata, and Ms. Yasuka Yoshida for their technical assistance.