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Ascaridole-rich essential oil from marsh rosemary (Ledum palustre) growing in Poland exerts insecticidal activity on mosquitoes, moths and flies without serious effects on non-target organisms and human cells

Benelli, Giovanni, Pavela, Roman, Cianfaglione, Kevin, Sender, Joanna, Danuta, Urban, Maślanko, Weronika, Canale, Angelo, Barboni, Luciano, Petrelli, Riccardo, Zeppa, Laura, Aguzzi, Cristina, Maggi, Filippo
Food and chemical toxicology 2020 v.138 pp. 111184
Culex quinquefasciatus, DNA damage, Daphnia magna, Eisenia fetida, Musca domestica, Rhododendron tomentosum, Spodoptera littoralis, botanical insecticides, chemotypes, comet assay, cypermethrin, cytotoxicity, earthworms, essential oils, fibroblasts, gas chromatography-mass spectrometry, human cell lines, humans, inhibitory concentration 50, insect pests, insect repellents, insecticidal properties, keratinocytes, lethal concentration 50, lethal dose 50, marshes, moths, nontarget organisms, p-cymene, rare species, rosemary, traditional medicine, Poland
Marsh rosemary (Ledum palustre, Ericaceae) has been widely used in the traditional medicine of various regions worldwide, and as insect repellent. Little is known on its essential oil insecticidal potential. This study explored the insecticidal effects of the essential oil obtained from L. palustre growing in Poland on selected insect pests and vectors. GC-MS analysis evidenced an uncommon chemotype characterized by ascaridole (35.3% as sum of cis-ascaridole and isoascaridole) and p-cymene (25.5%). The essential oil was effective against Culex quinquefasciatus, Spodoptera littoralis and Musca domestica, showing LC₅₀/LD₅₀ of 66.6 mg L⁻¹, 117.2 μg larva⁻¹ and 61.4 μg adult⁻¹, respectively. It was not toxic to non-target Eisenia fetida earthworms and moderately toxic to Daphnia magna microcrustaceans, over the positive control α-cypermethrin. The essential oil cytotoxicity on human keratinocytes and fibroblasts showed high IC₅₀ values (71.3 and 84.4 μg mL⁻¹, respectively). Comet assay data highlighted no DNA damages. Based on our findings, this essential oil, characterized by the ascaridole/p-cymene chemotype, could be a candidate for the formulation of botanical insecticides; large-scale production of green insecticides by this rare species may be assured by ex situ cultivation and biotechnological techniques.