Introduction
Pelargonium genus as perennial small shrubs compromises more than 250 species [
1],
P. graveolens (
Pelargonium roseum) is highly valued by industries for producing geranium essential oil [
2]. According to BS ISO 4371-2012,
P. graveolens essential oil from different geographical origins should have geraniol (5–20%), citronellol (18–43%), citronellyl formate (4–12%), geranyl formate (1–8%), and linalool (2–11%) as the main components [
3]. The chemical profile of
P. graveolens essential oil is affected from its geographical origin. The pharmacological effects of
P. graveolens essential oil such as antioxidant [
4,
5], antimicrobial [
6‐
9], anti-inflammatory [
10,
11] and wound healings [
12] activities is well documented. Furthermore, evaluation the antifungal activities of
P. graveolens essential oil have been the subject of different experimental studies [
13‐
16]. The antifungal activities of
P. graveolens essential oil were confirmed against
Trichophyton spp. [
15], and
Candida albicans [
13,
14,
16]. Although, there are one report on anti-dermatophyte effects of
P. graveolens essential oil against
Trichophyton spp. [
15], but there is no investigation to compare the anti-dermatophyte effects of
P. graveolens essential oils against different kinds of dermatophytes (
Microsporum canis,
M. gypseum,
Trichophyton rubrum,
T. mentagrophytes, and
T. schoenleinii).
Dermatophytes (
Trichophyton,
Microsperum,
Epidermophyton) are one of major cause of superficial fungal infections with an estimate lifetime risk of 20–25% [
17]. The use of topical and systemic drugs (Azoles/allylamines, terbinafine) is used for treatment of dermatophytes that are associated with adverse effects and appearance of resistant microbial strains [
18]. Different kinds of essential oils have been evaluated against dermatophytes.
Prunus armeniaca,
Prunus dulcis var. amara,
Olea europaea,
Mentha piperita [
19],
Artemisia sieberi [
20],
Juniperus communis ssp. alpina,
J. oxycedrus ssp.
oxycedrus and
J. turbinate [
21] were effective against dermatophytes.
Therefore, the subject of this study was to evaluate the anti-dermatophyte effects of nine different P. graveolens essential oils from Iran, Germany and India against dermatophytes.
Results and discussion
Essential oils are favorable natural compounds that can be used as natural alternative treatment for management of dermatophytosis. Citronellol (0.2–48.3%), geraniol (3.4–95.6%), citronellyl formate (0.3–16.2%), geranyl formate (1.6–10.8%), and linalool (0.7–13.4%) were the main components of 9 samples of
P. graveolens essential oils (Table
1). The highest and lowest amounts of geraniol (95.6%) and citronellol (0.2%) were found in
P. graveolens essential oil E
20 from India. Trans-caryophyllene was the second main component of this essential oil (3.5%), followed by geranyl formate (1.6%), and linalool (0.7%). The highest amounts of citronellol were in
P. graveolens essential oil E
21 (48.3%), E
9 (48.0%), E
11 (45.6%), and E
6 (41%).
Citronellol was the first main component of 8 samples of P. graveolens essential oils, while geraniol was the second main component of 2 samples of P. graveolens essential oils (E4 and E14). Linalool was the second main component of one sample P. graveolens essential oil. Citronellyl formate was found in 5 samples of P. graveolens essential oil as the second main component.
The chemical profiles and main components of
P. graveolens essential oil were changed from one sample to others. The chemical profile of
P. graveolens essential oils were not according to standard
P. graveolens essential oil (BS ISO 4371-2012) [
3].
The anti-dermatophyte effects of
P. graveolens essential oils against dermatophytes by mycelium growth inhibition test exhibited that
P. graveolens essential oil E
20 had the highest mycelium growth inhibition percent against dermatophytes (30.9–53.3%), followed by E
4 (17.8–43.6%) and E
14 (19.9–43.6%), respectively.
T. rubrum had the higher mycelium inhibition percent (22.5–53.3%) by
P. graveolens essential oils, followed by
M. gypseum (17–45.4%), and
T. mentagrophytes (16.5–43.6%).
M. canis and
T. schoenleinii had the less mycelium inhibition percent by
P. graveolens essential oils
(Table
2).
Table 2
Mycelium growth inhibition of dermatophytes by 200 ppm P. graveolens essential oils
E21 | 15.9 | 17.0 | 16.5 | 22.5 | 17.2 |
E6 | 14.5 | 23.1 | 20.4 | 31.8 | 13.9 |
E22 | 9.8 | 18.7 | 22.6 | 28.5 | 10.3 |
E14 | 19.9 | 25 | 22.8 | 35.0 | 16.0 |
E20 | 30.9 | 45.4 | 36.3 | 53.3 | 41.4 |
E3 | 14.0 | 20.7 | 15.8 | 28.5 | 11.3 |
E11 | 20.5 | 20.0 | 19.5 | 28.8 | 8.8 |
E4 | 17.8 | 23.3 | 43.6 | 26.8 | 16.1 |
E9 | 14.9 | 18.0 | 31.0 | 27.6 | 17.2 |
In micro-broth dilution assay, the MIC and MFC values for E
20 were in the ranges of 0.03–0.125 and 0.06–0.25 μl/ml, respectively. E
14 (MIC, MFC values of 0.06–0.125, 0.125–0.25 μl/ml), E
4 and E
21 (MIC, MFC values of 0.06–0.25, 0.125–0.5 μl/ml) showed anti-dermatophyte activity, followed by E
11, E
9 (MIC, MFC values of 0.125–0.25, 0.125–0.5 μl/ml), E
3 (MIC, MFC values of 0.125–0.25, 0.25–0.5) μl/ml), E
6 (MIC, MFC values of 0.125–0.5, 0.25–0.5 μl/ml). E
22 (MIC, MFC values of 0.125–0.5, 0.25–1 μl/ml) had the higher MIC and MFC values against dermatophytes than the others
(Table
3).Table 3
The antifungal activity of P. graveolens essential oils against dermatophytes
E3 | 0.25 | 0.25 | 0.25 | 0.5 | 0.125 | 0.25 | 0.125 | 0.25 | 0.25 | 0.5 |
E4 | 0.125 | 0.125 | 0.125 | 0.25 | 0.125 | 0.25 | 0.06 | 0.125 | 0.25 | 0.5 |
E6 | 0.125 | 0.25 | 0.125 | 0.25 | 0.125 | 0.25 | 0.125 | 0.25 | 0.25 | 0.5 |
E9 | 0.125 | 0.25 | 0.125 | 0.25 | 0.25 | 0.25 | 0.125 | 0.25 | 0.25 | 0.5 |
E11 | 0.125 | 0.125 | 0.25 | 0.25 | 0.125 | 0.25 | 0.125 | 0.25 | 0.25 | 0.5 |
E14 | 0.125 | 0.125 | 0.125 | 0.25 | 0.06 | 0.125 | 0.125 | 0.25 | 0.125 | 0.25 |
E20 | 0.06 | 0.125 | 0.125 | 0.25 | 0.03 | 0.06 | 0.06 | 0.125 | 0.125 | 0.25 |
E21 | 0.125 | 0.125 | 0.125 | 0.5 | 0.125 | 0.25 | 0.06 | 0.125 | 0.25 | 0.25 |
E22 | 0.125 | 0.125 | 0.25 | 0.5 | 0.25 | 0.5 | 0.25 | 0.5 | 0.5 | 0.5 |
Amphotericin | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.5 | 1 | 0.5 | 0.5 |
As the results of anti-dermatophyte screening exhibited that E20 with high amount of geraniol had the highest activity against dermatophytes, followed by E4, E14. Indeed the P. graveolens essential oils with high amount of citronellol and geraniol as the first and second main components had the higher anti-dermatophyte effects. The essential oil with high amounts of citronellol or citronellyl formate showed anti-dermatophytes effects lower than the essential oils with citronellol and geraniol as the main components.
The results of anti-dermatophyte effects of
P. graveolens essential oils have not been in according to their anti-candidal effects. There was no significant difference in anti-candidal activities of six samples of
P. graveolens essential oils with citronellol (7.7–43.7%) and geraniol (19.3–48.5%) against clinical isolates of
C. albicans in regard to inhibition zone diameters and the MIC and MFC values [
23].
The results of this study confirmed that corresponding components responsible for anti-dermatophyte activity of
P. graveolens essential oils were geraniol and citronellol. The mechanism of action for geraniol and citronellol is interfering with cell membrane of dermatophytes and decreasing the ergosterol content of cell by inhibition of ergosterol biosynthesis [
24,
25], while the anti-candidal activity against
C. albicans is not mediated by ergosterol biosynthesis [
26].
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