Euclasta condylotricha flowers essential oils: A new source of juvenile hormones and its larvicidal activity against Anopheles gambiae s.s. (Diptera: Culicidae)

Abstract

The essential oil (EO) of plants of the Poaceae family has diverse chemical constituents with several biological properties. But, data on the chemical constituents and toxicity are still unavailable for some species belonging to this family, such as Euclasta condylotricha Steud (Eu. condylotricha). In this study, the chemical composition of the EOs of Eu. condylotricha flowers was evaluated by gas chromatography coupled with mass spectrometry (GC–MS). The EOs larvicidal property was assessed against third instar larvae of three Anopheles gambiae laboratory strains (Kisumu, Acerkis and Kiskdr) according to the WHO standard protocol. The percentage yields of the EOs obtained from hydro distillation of Eu. condylotricha flowers varied 0.070 to 0.097%. Gas Chromatography-Mass Spectrometry (GC-MS) applied to the EOs revealed fifty-five (55) chemical constituents, representing 94.95% to 97.78% of the total essential oils. Although different chemical profiles of the dominant terpenes were observed for each sample, EOs were generally dominated by sesquiterpenoids with juvenile hormones as the major compounds. The primary compounds were juvenile hormone C16 (JH III) (35.97–48.72%), Methyl farnesoate 10,11-diol (18.56–28.73%), tau-Cadinol (18.54%), and β-Eudesmene (12.75–13.46%). Eu. condylotricha EOs showed a strong larvicidal activity with LC50 values ranging from 35.21 to 52.34 ppm after 24 hours of exposition. This study showed that Eu. Condylotricha flowers essential oils are potent sources of juvenile hormones that could be a promising tool for developing an eco-friendly malaria vector control strategy.

Larvicidal, Ovicidal, and Repellent Activities of Leucas stachydiformis (Hochst. ex Benth.) Briq Essential Oil against Anopheles arabiensis

“…stephensi [28] and Euclasta condylotricha (38.46 ppm) against An. gambiae [29] and Pinus sylvestris essential oil which exhibited signifcant larvicidal activity against D. gallinae larvae with LC 50 values of 0.68 mg/mL [30].…”

“…Larvicidal properties of the essential oil of L. stachydiformis may be linked to its major constituents such as caryophyllene oxide, germacrene D, linalool, and α-humulene which have been reported to have strong larvicidal properties [27,[29][30][31]. However, the efect of these major constituents might have been strengthened by the cooccurrence of minor compounds that act in an additive and/or synergistic manner [32].…”

“…However, the efect of these major constituents might have been strengthened by the cooccurrence of minor compounds that act in an additive and/or synergistic manner [32]. Among the minor constituents of the oil, α-pinene, verbenone, bicyclogermacrene, δ-cadinene, and α-terpineol were reported to have larvicidal activity [1,29,32,33]. Diferent phytochemicals are known to cause neurotoxicity or direct contact toxicity to the midgut epithelium of mosquito larvae [34].…”