Antifungal activity of some essential oil nanoemulsions against Saprolegniasis in rainbow trout (Oncorhynchus mykiss) eggs Antifungal activity of essential oil nanoemulsions

In this study, thyme (Coridothymus capitatus L.), laurel (Laurus nobilis), lavender (Lavandula officinalis), cumin (Cuminum cyminum), cinnamon (Cinnamon zeylanicum), and eucalyptus (Eucalyptus globulus) essential oil nanoemulsions were screened for their antifungal activity against isolated Saprolegnia parasitica strains by disc diffusion and tube dilution methods. The constituents of the essential oil nanoemulsions were analyzed using gas chromatography/mass spectrometry (GC/MS). The major constituents of the essential oils were carvacrol (46.17%) in thyme, eucalyptol (1,8-cineole; 45.57%) in laurel, linalyl acetate (32.95%) in lavender, thymoquinone (44.86%) in cumin, eugenol (58.59%) in cinnamon, and 1,8-cineole (68.97%) in eucalyptus. The thyme essential oil nanoemulsions were showed the highest antifungal potency (MIC; 50-100 mu L mL(- 1) and MLC; 100-125 mu L mL(- 1)) while cinnamon essential oil nanoemulsions were less effective (MIC; 250-500 mu L mL(- 1) and MLC; 500-1000 mu L mL(- 1)) against S. parasitica. The thyme essential oil nanoemulsions were more effective on fungal strains than the positive control group (formalin) at a range of 250-1000 mu L mL(- 1) concentrations. Following in vitro studies, the antifungal effect of thyme and cinnamon essential oil nanoemulsions was determined in rainbow trout eggs experimentally infected with S. parasitica strains. The highest survival rates were recorded in thyme essential oil nanoemulsions at 50 mg L- 1 (76.60%) and the positive control (81%) (p < 0.05). These results indicate that thyme and cinnamon essential oil nanoemulsions could be new plant-based antifungals against Saprolegniasis. Besides, they are eco-friendly and safe for use in aquaculture.