Geraniol

Pharm Biol. 2015 May 12:1-6.

Anti-Trichomonas vaginalis properties of the oil of Amomum tsao-ko and its major component, geraniol.[Pubmed: 25963227]

Trichomonosis, caused by the flagellate protozoan Trichomonas vaginalis, is the most common non-viral sexually transmitted disease (STD) and 5-nitroimidazole drugs are used for the treatment. However, a growing number of T. vaginalis isolates are resistant to these drugs, which make it becomes an urgent issue. The current study was designed to evaluate the anti-T. vaginalis activity of the essential oil from A. tsao-ko used in traditional Chinese medicine and as a spice and its main component, Geraniol.
METHODS AND RESULTS:
The anti-T. vaginalis activities of A. tsao-ko essential oil and Geraniol were evaluated by the minimum lethal concentration (MLC) and 50% inhibitory concentration (IC50) in vitro. The morphological changes of T. vaginalis were observed by transmission electron microscopy (TEM). Additionally, sub-MLC concentration treatment with sub-MLC A. tsao-ko essential oil and Geraniol was also performed. This study shows that MLC/IC50 of A. tsao-ko essential oil was 44.97 μg/ml/22.49 μg/ml for T. vaginalis isolate Tv1, and 89.93 μg/ml/44.97 μg/ml for T. vaginalis isolate Tv2. Those of Geraniol were 342.96 μg/ml/171.48 μg/ml, respectively. After A. tsao-ko essential oil or Geraniol treatment, obvious similar morphological changes of T. vaginalis were observed by TEM: the nuclear membrane was damaged, nuclei were dissolved, and the chromatin was accumulated; in the cytoplasm, numerous vacuoles appeared, rough endoplasmic reticulum dilated, the number of ribosomes were reduced, organelles disintegrated, the cell membrane was partially damaged, with cytoplasmic leakage, and cell disintegration was observed. The action time did not increase the effect of A. tsao-ko essential oil or Geraniol against T. vaginalis, as no significant difference was observed after sub-MLC concentration treatment for 1, 3, and 5 h with A. tsao-ko essential oil and Geraniol.
CONCLUSIONS:
The study describes the first report on the activity and morphological changes of A. tsao-ko essential oil and Geraniol against T. vaginalis. The results obtained herein presented new opportunities for antitrichomonal drugs.

Basic Clin Pharmacol Toxicol. 2014 Dec;115(6):534-44.

Geraniol blocks calcium and potassium channels in the Mammalian myocardium: useful effects to treat arrhythmias.[Pubmed: 24862086]

Geraniol is a monoterpene present in several essential oils, and it is known to have a plethora of pharmacological activities. In this study, we explored the contractile and electrophysiological properties of Geraniol and its antiarrhythmic effects in the heart.
METHODS AND RESULTS:
The Geraniol effects on atrial contractility, L-type Ca(2+) current, K(+) currents, action potential (AP) parameters, ECG profile and on the arrhythmia induced by ouabain were evaluated. In the atrium, Geraniol reduced the contractile force (~98%, EC = 1,510 ± 160 μM) and diminished the positive inotropism of CaCl2 and BAY K8644. In cardiomyocytes, the IC a,L was reduced by 50.7% (n = 5) after perfusion with 300 μM Geraniol. Moreover, Geraniol prolonged the AP duration (APD) measured at 50% (n = 5) after repolarization, without changing the resting potential. The increased APD could be attributed to the blockade of the transient outward K(+) current (Ito ) (59.7%, n = 4), the non-inactivation K(+) current (Iss ) (39.2%, n = 4) and the inward rectifier K(+) current (IK 1 ) (33.7%, n = 4). In isolated hearts, Geraniol increased PRi and QTi without affecting the QRS complex (n = 6), and it reduced both the left ventricular pressure (83%) and heart rate (16.5%). Geraniol delayed the time to onset of ouabain-induced arrhythmias by 128%, preventing 30% of the increase in resting tension (n = 6).
CONCLUSIONS:
Geraniol exerts its negative inotropic and chronotropic responses in the heart by decreasing both L-type Ca(2+) and voltage-gated K(+) currents, ultimately acting against ouabain-induced arrhythmias.

Med Mycol. 2015 Apr 1;53(3):275-84.

Investigating the antifungal activity and mechanism(s) of geraniol against Candida albicans strains.[Pubmed: 25480017]

Candida albicans can be a yeast that is a commensal on the human body but can cause opportunistic or pathogenic infections. Candida infections may create serious health problems and as a result has initiated a search for new drugs with an antifungal action. Geraniol is an acyclic monoterpene alcohol with known pharmacological properties, including antimicrobial activity. The aim of this work was to evaluate the antifungal activity and mechanism(s) of Geraniol against C. albicans strains. The minimum inhibitory concentration (MIC) was determined through broth microdilution techniques.
METHODS AND RESULTS:
We investigated possible Geraniol activity on the fungal cell wall (sorbitol protect effect), cell membrane (Geraniol to ergosterol binding), the time-kill curve, and its biological activity on the yeast's morphology. Amphotericin B was used as control, and all tests were performed in duplicate. The MIC of Geraniol was 16 μg/ml (for 90% of isolates) but its probable mechanism of action did not involve the cell wall and ergosterol binding. In the morphological interference assay, we observed that the product inhibited pseudohyphae and chlamydoconidia formation. Time-dependent kill curve assay demonstrated that the fungicidal activity for MIC × 2 started at 2 h for the ATCC 76485 strain, and at 4 h for the LM-70 strain. Geraniol showed in vitro antifungal potential against strains of C. albicans but did not involve action on the cell wall or ergosterol.
CONCLUSIONS:
This study contributes to the development of new antifungal drugs, especially against Candida spp.

Contact Dermatitis. 2014 Nov;71(5):280-8.

Cross-reactivity between citral and geraniol - can it be attributed to oxidized geraniol?[Pubmed: 25209002]

The fragrance compound Geraniol is susceptible to autoxidation when in contact with air, and to cutaneous metabolism. In both processes, the isomeric aldehydes geranial and neral are formed. Citral consists of geranial and neral. Among patients with positive reactions to citral, we have previously detected concomitant reactions to Geraniol in 85% of cases and to oxidized Geraniol in 73% of cases. To study the pattern of concomitant reactions to Geraniol and citral and its isomers geranial and neral, and to determine whether these isomers are important sensitizers in contact allergy to Geraniol and oxidized Geraniol.
METHODS AND RESULTS:
The irritancy of geranial and citral was studied. Six hundred and fifty-five patients were patch tested with geranial, neral and citral at 3.5% pet., pure Geraniol at 6.0% and 11.0% pet., and oxidized Geraniol at 6.0% pet. Twenty-six per cent of citral-positive patients reacted to oxidized Geraniol, and 10.5% reacted to pure Geraniol. Citral and/or its isomers gave positive reactions in 25% of the patients who reacted to pure Geraniol.
CONCLUSIONS:
There is little cross-reactivity between pure Geraniol and citral; however, concomitant reactions to citral and oxidized Geraniol were common, owing to geranial. Geranial was also the main sensitizer in the mixture citral.