Antimicrobial Activity, Larvicidal Efficacy and Chemical Composition of Essential Oil from the Rhizome of Alpinia napoensis

Essential oil hydrodistilled from the rhizomes of Alpinia naopensis H.G. Dong & G.J. Xu was characterised by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The antimicrobial activity was evaluated by microdilution broth susceptibility assay while the larvicidal efficacy on Aedes albopictus and Culex quinquefasciatus was determined by the World Health Organization protocol. The main constituents of the essential oil were 1,8-cineole (18.2 %), γ-terpinene (12.5 %), terpinene-4-ol (9.6 %), β-pinene (9.2 %) and fenchyl acetate (7.7 %). From the antimicrobial study, the essential oil showed activity towards six of the eight tested microorganisms with MIC < 50.0 μg/mL. At concentration 100 μg/mL, the essential oil exhibited 100 % mortality towards Ae. albopictus and Cx. quinquefasciatus under 24 h and 48 h. The oil displayed larvicidal activity against Ae. albopictus with median lethal concentrations (LC50) values of 56.39 μg/mL (24 h) and 53.85 μg/mL (48 h), as well LC50 values of 46.67 μg/mL (24 h) and 38.29 μg/mL (48 h) towards Cx. quinquefasciatus.