Analysis of the Essential Oil of Elsholtzia ciliate Aerial Parts and Its Insecticidal Activities against Liposcelis bostrychophila

Water-distilled essential oil from Elsholtzia ciliate (Labiatae) aerial parts at flowering stage was analyzed by gas chromatography/mass spectrometry (GC/MS). Thirty-six compounds, accounting for 98.3% of the total oil content, were identified, and the main components of the essential oil were dehydroelsholtzia ketone (26.5%), ( R )-carvone (16.6%), elsholtzia ketone (14.6%), and D -limonene (4.1%). The essential oil contained higher amounts of monoterpenoids (83.4%) than of sesquiternoids (8.3%). Bioactivity-directed chromatographic separation of the essential oil on repeated silica gel columns led to the isolation of three monoterpenoids. The essential oil possessed fumigant toxicity against the booklice ( Liposcelis bostrychophila ) with an LC 50 value of 475.2 μg/l, while the isolated constituents, ( R )-carvone, dehydroelsholtzia ketone, and elsholtzia ketone had LC 50 values of 417.4, 658.2, and 547.3 μg/l, respectively. The essential oil also exhibited contact toxicity against L. bostrychophila with an LC 50 value of 145.5 μg/cm 2 . ( R )-Carvone, dehydroelsholtzia ketone, and elsholtzia ketone exhibited acute toxicity against the booklice with LC 50 values of 57.0, 151.5, and 194.1 μg/cm 2 , respectively. The results indicated that the essential oil and the isolated constituents have potential for the development into natural insecticides/fumigants for the control of insects in stored grains.