Essential Oil Composition and Larvicidal Activity of Clinopodium gracile (Benth) Matsum (Labiatae) Aerial Parts against the Aedes albopictus Mosquito

Purpose: To determine larvicidal activity of essential oil derived from Clinopodium gracile (Benth.) Matsum. (Labiatae) aerial parts against the larvae of Aedes albopictus Skuse．Methods: Essential oil of C. gracile aerial parts was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The activity of the essential oil was evaluated, using World Health Organization (WHO) procedures, against the fourth larvae of A. albopictus for 24 h and larval mortality recorded at a various essential oil concentrations ranging from 12.5 – 200.0 μg/mL.Results: A total of 34 components of the essential oil of C. gracile were identified. The essential oil has higher content of sesquiterpenoids (70.49 %) than monoterpenoids (12.21 %). The other principal compounds of the essential oil were germacrene D (20.59 %), nootkatone (8.22 %), morillol (7.74 %), β- elemene (7.38 %), α-bergamotene (6.08 %), cis-β-farnesene (5.47 %) and caryophyllene (5.17 %). The essential oil exhibited larvicidal activity against A. albopictus with a median lethal concentration (LC50) of 42.56 μg/mL.Conclusion: The findings obtained indicate that the essential oil of C. gracile has potentials for use in the control of A. albopictus larvae and could be useful in the search for new, safer and more effective natural compounds as larvicides.Keywords: Clinopodium gracile, Aedes albopictus, Larvicidal activity, Mosquito, Essential oil