Larvicidal, molluscicidal and nematicidal activities of essential oils and compounds from Foeniculum vulgare

Plant-based products, namely essential oils (EOs), are environmentally friendly alternatives for the control of disease vectors, hosts and/or parasites. Here, we studied the general toxicity and biopesticidal potential of EOs and phenylpropanoids from Foeniculum vulgare var. vulgare (bitter fennel), a perennial plant well adapted to temperate climates. EO/compound toxicity was tested against a freshwater snail and potential intermediate host of Fasciola hepatica (Radix peregra), a mosquito and former European malaria vector (Anopheles atroparvus) and one of the most damaging plant-parasitic nematodes, the root-knot nematode (Meloidogyne javanica). Lethal concentrations (LC50; LC90) of EOs (infrutescences/stems with leaves) and compounds were calculated by probit analysis. All displayed noteworthy activity against R. peregra adults (LC50 21-39 A mu g ml(-1)) and A. atroparvus larvae (LC50 16-56 A mu g ml(-1)). trans-Anethole revealed acute nematicidal activity after 24 and 48 h (LC50 310 and 249 A mu g ml(-1), respectively), and estragole (1,000 A mu g ml(-1)) showed some effectiveness against M. javanica hatching and juveniles after 15 days. Plant and EO yields were determined to evaluate the bitter fennel productivity. The chemical composition of the EOs was analyzed by gas chromatography coupled to mass spectrometry. EOs extracted from whole plants, infrutescences and stems with leaves were characterized by estragole-dominant profiles (28-65 %), considerable amounts of phellandrene (10-34 %) and fenchone (6-16 %), and minor trans-anethole contents (1-4 %). Although additional toxicological studies against nontarget organisms are required, our study demonstrates that bitter fennel is a productive source of molluscicides and larvicides, and thus a potential sustainable biological agent to control particular host species, namely freshwater snails and mosquitoes.We would like to thank Jose Ferreira and Diara Rocha from the IHMT for the mosquito colony maintenance and larvae production and collaborators from the Nematology Laboratory of the University of Coimbra for kindly providing the nematode isolate. The authors are grateful to Susana Chaves for improving the use of English in the manuscript. This research was supported by FEDER through POFC-COMPETE and by Portuguese funds through the projects (PIDDAC)-PEst-OE/BIA/UI4050/2014 and PEst-OE/AGR/UI4033/2014. R.M. Sousa was supported by the Portuguese Foundation for Science and Technology (FCT) through a PhD grant (SFRH/BD/66041/2009).info:eu-repo/semantics/publishedVersio

Essential Oils from Aromatic and Medicinal Plants as Effective Weapons Against Mosquito Vectors of Public Health Importance

The fight against mosquito-borne diseases has recently seen the failure of control programmes based on synthetic chemical treatments to combat larvae and adults of mosquito vectors. This has led to several problems linked to residual substances causing a detrimental impact on environment and human health and to the development of resistance in mosquitoes. In this scenario, new eco-friendly and alternative strategies for the management of mosquito-borne diseases come from the use of plant essential oils (EOs). These are complex mixtures of small, volatile and lipophilic compounds, mostly belonging to monoterpenoids, sesquiterpenoids and phenylpropanoids, produced by aromatic plants belonging to several botanical families such as Apiaceae, Asteraceae, Geraniaceae, Lamiaceae, Lauraceae, Myrtaceae, Poaceae, Rutaceae, Verbenaceae and Zingiberaceae. An important ecological role played by EOs is defending plants from several enemies such as bacterial and fungal pathogens, viruses, insects and parasites. EOs represent ideal candidate ingredients to be incorporated in insecticidal formulations since scientific evidences have documented their efficacy against larvae and adults of several mosquitoes (e.g. Anopheles, Aedes and Culex) even at low doses (<50 ppm), the multiple mode of action and wide spectrum of efficacy, the low toxicity on nontarget organisms and environment and the unlikely capacity to induce insect resistance. In this chapter, we gave an overview of the most important EOs obtained from commercially important botanical families with documented efficacy against mosquito vectors. Particular attention has been paid to highlight their strengths and weakness and the future challenges leading to the replacement of conventional insecticides by agrochemical companies