Antifungal and Phytotoxic Activities of Essential Oils: In Vitro Assays and Their Potential Use in Crop Protection

Abstract

(1) Background: The use of natural products based on essential oils (EO) is nowadays arousing great interest as an alternative method to control plant pathogens and weeds. However, EO possess low bioavailability and are highly volatile, and their encapsulation in hydroxypropyl-ß-cyclodextrin (HP-β-CD) could be a means to enhance their stability and maintain their bioactivity. Thus, the current study aims at investigating, in the presence and the absence of HP-β-CD, the antifungal and phytotoxic activities of nine EO, distilled from plant species belonging to Alliaceae, Apiaceae, and Cupressaceae families, with considerations for their chemical composition. (2) Methods: EO antifungal activity was assessed by direct contact and volatility assays against Fusarium culmorum, a major phytopathogenic fungi, while phytotoxic effects were evaluated against lettuce (Lactuca sativa L.) and rye-grass (Lolium perenne L.), by seedling’s emergence and growth assays. (3) Results: These EO inhibit fungal growth in both direct contact and volatility assays, with half-maximal inhibitory concentrations (IC50) ranging from 0.01 to 4.2 g L−1, and from 0.08 up to 25.6 g L−1, respectively. Concerning phytotoxicity, these EO have shown great potential in inhibiting lettuce (IC50 ranging from 0.0008 up to 0.3 g L−1) and rye-grass (IC50 ranging from 0.01 to 0.8 g L−1) seedlings’ emergence and growth. However, the EO encapsulation in HP-β-CD has not shown a significant improvement in EO biological properties in our experimental conditions. (4) Conclusion: All tested EO present antifungal and phytotoxic activities, with diverse efficacy regarding their chemical composition, whilst no increase of their biological effects was observed with HP-β-CD.

Chemical Composition, Antioxidant and Anti-Inflammatory Activities of Clary Sage and Coriander Essential Oils Produced on Polluted and Amended Soils-Phytomanagement Approach

“…EO were analysed by electron ionization gas chromatography–mass spectrometry (QP 2010 Ultra, Shimadzu, Marne-la-Vallée, France). The system was operated using helium as a carrier gas at a constant linear velocity (60 cm s − 1 ), as previously described [ 73 ]. Essential oil’s samples were first diluted in ethyl acetate (ratio 1:200 ( v / v )) and 0.2 µL of the resulting solution was injected in a split mode (split ratio 1:10) in a ZB-5MS (5%-phenyl-arylene/95% dimethylpolysiloxane—10 m length, 0.10 mm inner diameter, 0.10 μm phase thickness—Phenomenex, Le Pecq, France) capillary column.…”

“…The capacity of the β -CD to encapsulate EO (retention capacity) was quantified through a static headspace-gas chromatography (SH-GC) analysis, performed according to [ 73 ]. Briefly, EO were added to 10 mL of either water or 10 mM aqueous β -CD solutions in 22 mL headspace glass vials.…”

In Vitro Potential of Clary Sage and Coriander Essential Oils as Crop Protection and Post-Harvest Decay Control Products

“…Essential oils' antifungal activity against F. culmorum was evaluated by using an in vitro direct contact assay. It was evaluated according to the method previously described [19,50], with slight modifications. A PDA medium (39 g L −1 ) was first prepared, complemented with 1% (v/v) DMSO (Thermo Fisher Scientific, Illkirch, France), in which EO were mixed at 50 • C, so as to obtain a final scale of 5 EO concentrations, ranging from 0.005 to 1.0% (v/v) of EO in the medium.…”

“…As part of an integrated pest management system, the use of natural products, including EO, considered as biocontrol tools, is then greatly encouraged [16,17], especially in the current context, where regulatory restrictions lead to the withdrawal of several commercial products [15,18]. Owing to their relatively low toxicity for humans and animals, EO are moreover registered as "Generally Recognized As Safe (GRAS)" products by the Food and Drug Administration, and regarded as less harmful to both environmental and human health, in comparison with commercial pesticides [19,20]. They also receive increasing public support, considered as eco-friendly products [4,20].…”

“…To tackle these problems, the use of appropriate EO formulations could offer a promising tool [4,5,21]. In particular, the use of β-cyclodextrins (β-CD), cyclic oligosaccharides able to encapsulate hydrophobic compounds in aqueous solutions, and cited in the Food and Drug Administration's list of Inactive Pharmaceutical Ingredients, may be of great interest to avoid degradation, while maintaining the products' efficiency [19,22].…”