Abstract
Developing effective and eco-friendly antiparasitic drugs and insecticides is an issue of high importance nowadays. In this study, we evaluated the anthelminthic and insecticidal potential of the leaf essential oil obtained from Origanum syriacum against the L3 larvae of the parasitic nematode Anisakis simplex and larvae and adults of the mosquito Culex quinquefasciatus. Tests on A. simplex were performed by standard larvicidal and penetration assays, while mosquito toxicity was assessed relying on larvicidal, tarsal contact, and fumigation tests. To shed light on the possible mode of action, we analyzed the oil impact as acetylcholinesterase (AChE) inhibitor. This oil was particularly active on L3 larvae of A. simplex, showing a LC50 of 0.087 and 0.067 mg mL−1 after 24 and 48 h treatment, respectively. O. syriacum essential oil was highly effective on both larvae and adults of C. quinquefasciatus, showing LC50 values of 32.4 mg L−1 and 28.1 µg cm−2, respectively. Its main constituent, carvacrol, achieved larvicidal LC50(90) of 29.5 and 39.2 mg L−1, while contact toxicity assays on adults had an LC50(90) of 25.5 and 35.8 µg cm−2, respectively. In fumigation assays, the LC50 was 12.1 µL L−1 after 1 h and decreased to 1.3 µL L−1 in 24 h of exposure. Similarly, the fumigation LC50 of carvacrol was 8.2 µL L−1 after 1 h of exposure, strongly decreasing to 0.8 µL L−1 after 24 h of exposure. These results support the folk usage of Lebanese oregano as an antiparasitic agent, providing new insights about its utilization for developing new effective and eco-friendly nematocidal and insecticidal products.
Highlights
The development of new drugs to fight parasitic infections such as anisakiasis is highly needed.Anisakiasis, the parasitic infection of the gastrointestinal tract caused by the members of the genusAnisakis, such as A. simplex Dujardin larvae, is a public health concern worldwide, in Asian countries such as Japan, and in Mediterranean areas, such as Spain and Italy [1,2]
We investigated whether one of the possible modes of action of the O. syriacum essential oil may be the inhibition of acetylcholinesterase (AChE), an enzyme ensuring the breakdown of acetylcholine, which acts as a neurotransmitter in both invertebrate species
Penetration assay data showed that A. simplex larvae did not penetrate in the agar treated with O. syriacum essential oil at the LC50 concentration
Summary
The development of new drugs to fight parasitic infections such as anisakiasis is highly needed.Anisakiasis, the parasitic infection of the gastrointestinal tract caused by the members of the genusAnisakis, such as A. simplex Dujardin larvae, is a public health concern worldwide, in Asian countries such as Japan, and in Mediterranean areas, such as Spain and Italy [1,2]. Among Culex species of medical relevance, Culex quinquefasciatus Say attracts the attention of scientists worldwide being the main vector of filariasis, currently recognized as one of the most important neglected tropical diseases [10,11], while its competence as a Zika virus vector is still debated [12,13,14]. The management of this mosquito species is based on the employment of synthetic insecticides though this is challenged by the quick development of resistance in targeted populations [15]. In agreement with the Integrated Vector Management (IVM) [16] and One Health criteria [17,18], the development of novel and environmentally sustainable ovicides, larvicides, and pupicides to be used in aquatic environments, as well as adulticides and repellents, is a major target for current entomological research [19,20,21,22]
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